Features of dissociation differentially predict antidepressant response to ketamine in treatment-resistant depression

How-To Study Dissociative Symptoms in a Broad Range of Mental Disorders: A Methodological Primer

Dissociative symptoms constitute a transdiagnostic phenomenon not only characterizing dissociative disorders but also occurring across a broad range of other mental disorders such as posttraumatic stress disorder or borderline personality disorder. In the latter disorders, dissociative symptoms such as depersonalization, derealization, or gaps in awareness significantly burden patients' wellbeing and functioning. Many efforts have been undertaken to better understand these debilitating symptoms. However, empirical findings have not yet converged in many areas (e.g., considering neurobiological correlates or effects of dissociative psychopathology on treatment outcome), which might partially be due to the heterogeneity and limitations of employed methodology. Here, we critically review the current state-of-the-art methodology in dissociation research, comparing methods to assess dissociative symptoms, provoke dissociative symptoms in the laboratory, select the participant sample, and consider critical sample characteristics. Discussing the informative value and limits of various standard and novel methodological approaches, we aim to provide information and nuanced guidance for future research. By these means, we aim to raise and harmonize standards in dissociation research and enable researchers of all career stages to enter, navigate, and make a significant and lasting contribution to research on dissociative symptoms in a broad range of mental disorders, ultimately contributing to a better understanding of dissociative psychopathology.

Psychedelic Drugs in Mental Disorders: Current Clinical Scope and Deep Learning-Based Advanced Perspectives

Mental disorders are a representative type of brain disorder, including anxiety, major depressive depression (MDD), and autism spectrum disorder (ASD), that are caused by multiple etiologies, including genetic heterogeneity, epigenetic dysregulation, and aberrant morphological and biochemical conditions. Psychedelic drugs such as psilocybin and lysergic acid diethylamide (LSD) have been renewed as fascinating treatment options and have gradually demonstrated potential therapeutic effects in mental disorders. However, the multifaceted conditions of psychiatric disorders resulting from individuality, complex genetic interplay, and intricate neural circuits impact the systemic pharmacology of psychedelics, which disturbs the integration of mechanisms that may result in dissimilar medicinal efficiency. The precise prescription of psychedelic drugs remains unclear, and advanced approaches are needed to optimize drug development. Here, recent studies demonstrating the diverse pharmacological effects of psychedelics in mental disorders are reviewed, and emerging perspectives on structural function, the microbiota-gut-brain axis, and the transcriptome are discussed. Moreover, the applicability of deep learning is highlighted for the development of drugs on the basis of big data. These approaches may provide insight into pharmacological mechanisms and interindividual factors to enhance drug discovery and development for advanced precision medicine.

Ketamine's Altered States Meta-Analysis: The Relationship Between Psychomimetic and Clinical Effects With Focus in Depression

BACKGROUND

In recent years, there has been a significant focus on exploring the potential therapeutic impact of altered states of consciousness on treatment outcomes for mental illness, with the goal of enhancing therapeutic strategies and patient results.

METHODS

This meta-analysis was designed to investigate the potential link between the psychomimetic effects of ketamine and clinical outcomes in mental health, which adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.

RESULTS

Eleven studies were selected for meta-analysis, and the main result did not find a significant correlation between the psychoactive effects of ketamine and clinical outcomes either in mental illness (n = 11; n's = 27; r = 0.06 [-0.05, 0.17]; P = 0.268) or depression exclusively (n = 10; n's = 25; r = 0.03 [-0.07, 0.13]; P = 0.561). High heterogeneity was found for general analysis ( I2 = 80.78). Egger's regression did not indicate publication bias (intercept = 1.57; SE = 1.49, P = 0.30). No significant Kendall's rank correlation coefficient was observed ( τ = 0.02, P = 0.88) indicating funnel plot symmetry. The sub-analyses, aimed at minimizing study variability by specifically examining factors such as patient disorders (limited to depression), methods of administration (exclusively intravenous), types of assessment instruments, and the timing of evaluations, also yielded no significant findings.

CONCLUSION

This meta-analysis suggests that the altered states of consciousness experienced during ketamine sessions are not directly linked to clinical outcomes. However, it is important to acknowledge that the limited number of studies and their heterogeneity render this conclusion preliminary, warranting further investigation over time.

Arketamine: a scoping review of its use in humans

Arketamine (R-ketamine), an enantiomer of ketamine, has historically been less studied than esketamine (S-ketamine) and the racemic mixture. Recent preclinical studies suggest that arketamine may offer prolonged antidepressant effects and a superior safety profile. This scoping review aims to assess and synthesise existing literature on the clinical use of arketamine in humans. This review follows the PRISMA for Scoping Reviews guidelines, with a comprehensive search conducted in PubMed, Embase, ClinicalTrials.gov, and the WHO International Clinical Trials Registry. Eligible studies included those reporting the administration of arketamine to humans. Data were extracted and synthesised descriptively. A total of 20 studies involving 410 subjects were included. Arketamine was primarily investigated for pain management and depression. While early evidence suggests arketamine may be effective in reducing pain, most studies were small and conducted in non-clinical settings. In psychiatry, trials indicate potential antidepressant effects, but results are inconsistent, and some studies remain unpublished. A consistent observation across most studies is arketamine's favourable safety profile, showing lower incidences of dissociative and psychotomimetic effects compared to esketamine and racemic ketamine. Arketamine may have a role in pain management and psychiatry, with a favourable safety profile compared to other forms of ketamine. However, the small scale of many studies limits the generalizability of findings, and results in depression trials are mixed. Larger, well-designed studies, possibly with higher doses, are needed to determine its therapeutic potential and establish its place in clinical practice.

Personalized use of ketamine and esketamine for treatment-resistant depression

A large and disproportionate portion of the burden associated with major depressive disorder (MDD) is due to treatment-resistant depression (TRD). Intravenous (R,S)-ketamine (ketamine) and intranasal (S)-ketamine (esketamine) are rapid-acting antidepressants that can effectively treat TRD. However, there is variability in response to ketamine/esketamine, and a personalized approach to their use will increase success rates in the treatment of TRD. There is a growing literature on the precision use of ketamine in TRD, and the body of evidence on esketamine is still relatively small. The identification of reliable predictors of response to ketamine/esketamine that are easily translatable to clinical practice is urgently needed. Potential clinical predictors of a robust response to ketamine include a pre-treatment positive family history of alcohol use disorder and a pre-treatment positive history of clinically significant childhood trauma. Pre-treatment versus post-treatment increases in gamma power in frontoparietal brain regions, observed in electroencephalogram (EEG) studies, is a promising brain-based biomarker of response to ketamine, given its time of onset and general applicability. Blood-based biomarkers have shown limited usefulness, with small-effect increases in brain-derived neurotrophic factor (BDNF) being the most consistent indicator of ketamine response. The severity of treatment-emergent dissociative symptoms is typically not associated with a response either to ketamine or esketamine. Future studies should ensure that biomarkers and clinical variables are obtained in a similar manner across studies to allow appropriate comparison across trials and to reduce the signal-to-noise ratio. Most predictors of response to ketamine/esketamine have modest effect sizes; therefore, the use of multivariate predictive models will be needed.

Psychometric properties of the 23-Item Clinician Administered Dissociative States Scale (CADSS) in a psychological trauma population

OBJECTIVE

Dissociative symptoms are both a pathological consequence of exposure to psychological trauma as well as a side effect of N-methyl-d-aspartate (NMDA) receptor antagonist medications; therefore, accurate and valid assessment of these symptoms is important. The psychometric properties of the 23-item Clinician Administered Dissociative States Scale (CADSS) have been characterized in the ketamine and esketamine literatures. Here, we examine its performance in a sample with and without posttraumatic stress disorder (PTSD) and a history of exposure to psychological trauma.

METHODS

Participants with a history of psychological trauma with (N = 148) and without (N = 100) the diagnosis of PTSD and healthy participants without a psychiatric disorder or history of trauma (N = 28) were assessed with the 23-item CADSS and other psychometric and neuropsychological assessments. Analyses were performed to examine internal consistency, convergent and discriminant validity, factor structure, differential performance in populations reported to be more or less likely to report dissociative symptoms (e.g., patients with and without PTSD), and sensitivity to change resulting from exposure to trauma-related sights and sounds.

RESULTS

The 23-item CADSS was found to have high internal consistency (Cronbach's alpha 0.91) and a single-factor structure. CADSS total scores in trauma-exposed participants with PTSD were higher than those in trauma-exposed participants without PTSD and non-traumatized non-PTSD participants. Finally, veterans with Iraq combat-related PTSD showed a significant increase in CADSS total score after exposure to combat-related slides and sounds.

CONCLUSION

The 23-item CADSS, already validated as a tool to measure dissociation related to administration of NMDA receptor antagonist medication, performs in a reliable and valid manner in the assessment of dissociation in psychologically traumatized participants.

Ketamine-induced altered states of consciousness: a systematic review of implications for therapeutic outcomes in psychiatric practices

This systematic review aims to elucidate the nexus between ketamine's psychoactive properties and its efficacy in treating a broad spectrum of psychiatric disorders. We searched three databases and used citation tracking to include 29 studies. Predominantly, mood disorders, including bipolar disorder (BD) and major depressive disorder (MDD) (MDD + BD: + n = 25 studies), a large part of them involve treatment-resistant patients (n = 14 studies), substance use disorder (SUD, n = 3 studies), and social anxiety disorder (SAD, n = 1 study). From all included studies (n = 29), 15 (51.72%) of them identified a positive relation between ketamine-induced altered states of consciousness and clinical outcomes, while 13 studies (44.83%) showed no linkage between them, and one study (3.45%) delineated a negative association. Focusing solely on intravenous (IV) ketamine infusions (n = 25), 14 studies (56%) reported a positive modulation of ketamine's psychoactive effects and therapeutic benefits, whereas 10 studies (40%) confirmed no relationship, and one study (4%) showed a negative association. The single study (33.34%) involving subcutaneous ketamine and all three studies (66.6%) intranasal administration did not demonstrate a significant interaction between ketamine's psychoactive effects and therapeutic response. All three SUD studies reported a positive correlation between ketamine's psychoactive effects and therapeutic response. In contrast, the single SAD study did not find a relationship between these parameters. For studies involving mood disorders (n = 25), 12 studies (48%) reported a positive relationship between psychoactive effects and therapeutic response. Others 12 studies (48%) identified a null relationship, and one study (4%) found a significant negative association. Although we have found a larger association than previous studies between ketamine's psychoactive properties and its efficacy in treating a broad spectrum of psychiatric disorders, its topic remains indeterminate, mainly due to the high heterogeneity.

Therapeutic Protocols Using Ketamine and Esketamine for Depressive Disorders: A Systematic Review

Depression is one of the most prevalent mental health disorders globally, causing severe emotional suffering, reducing life expectancy and increasing the risk of suicide. Recently, the use of dissociative psychedelic substances such as ketamine and esketamine for depressive disorders has expanded treatment options. We sought to analyze, through a systematic review, the existing protocols for the treatment of depression with ketamine and esketamine. The search adopted PRISMA criteria and was performed using PubMed and Web of Science databases. Procedures in each study were compared, focusing on the sample recruited, therapeutic approaches, including the clinical team and professionals engaged in treatment, medical procedures, description of the setting (including music) and factors such as specific medication (ketamine or esketamine), route of administration and dosage employed. Results indicated the predominance of a medical approach, with a limited number of studies on ketamine assisted psychotherapy (KAP) and other modalities of psychedelic assisted therapy. Additionally, there is limited information on psychosocial elements such as preparation, psychological support during session and integration of experience. Altogether these findings suggest that treatment of depression with ketamine or esketamine diverges in relation to the practices employed with psychedelic substances. This is discussed considering future research directions in the field.

Disembodiment and Affective Resonances in Esketamine Treatment of Depersonalized Depression Subtype: Two Case Studies

INTRODUCTION

Dissociative experiences are considered undesirable ketamine's adverse events. However, they might be crucial for ketamine's antidepressant effects, at least in some depression subtypes. Current understandings of ketamine's therapeutic potentials converge on the so-called "relaxed prior hypothesis," suggesting that glutamatergic blockage up-weights bottom-up surprising somatosensory/affective states. As a result, ketamine improves short-term plasticity in depression by enhancing sensitivity to interoceptive signals.

METHODS

We selected 2 case studies for their paradigmatic description of "depersonalized depression" (Entfremdungsdepression) symptoms. Patients were included in a 6-month-long esketamine program for treatment resistant depression, during which we collected their spontaneous experience with esketamine. According to a neurophenomenological approach, we combined subjective reports from unstructured clinical interviews and the review of previous objective neuroimaging results and neurocomputational models to unveil the relation between esketamine antidepressant effects and interoceptive sensitivity.

RESULTS

According to our clinical observations, esketamine-induced dissociation might be particularly effective in the depersonalized depression subtype, in which interoceptive awareness and interaffectivity are particularly compromised. Ketamine and esketamine's dissociative effects and particularly disembodiment might suspend previously acquired patterns of feeling, sensing, and behaving.

CONCLUSIONS

Coherently with previous research, we suggest that esketamine-induced disembodiment allows for a transient window of psychological plasticity and enhanced sensitivity, where the body recovers its permeability to affective affordances.

The Use of Ketamine for the Treatment of Anhedonia in Depression

Anhedonia, a complex symptom rooted in deficits across reward processes, is primarily linked to depression and schizophrenia but transcends diagnostic boundaries across various mental disorders. Its presence correlates with poorer clinical outcomes, including an increased risk of suicide and diminished response to treatment. The neurobiological underpinnings of anhedonia remain incompletely understood despite advancements in biomarkers and imaging that contribute to deeper insights. Ketamine, known for its rapid-acting antidepressant properties, appears to possess antianhedonic effects through a mechanism of action not fully elucidated. This effect appears to be independent of its antidepressant properties. Explorations into alternative antianhedonic treatments have been underway, yet lingering questions persist, underscoring the imperative need for ongoing research to advance the field.

Enhancing Agency in Posttraumatic Stress Disorder Therapies Through Sensorimotor Technologies

Posttraumatic stress disorder (PTSD) is a significant public health concern, with only a third of patients recovering within a year of treatment. While PTSD often disrupts the sense of body ownership and sense of agency (SA), attention to the SA in trauma has been lacking. This perspective paper explores the loss of the SA in PTSD and its relevance in the development of symptoms. Trauma is viewed as a breakdown of the SA, related to a freeze response, with peritraumatic dissociation increasing the risk of PTSD. Drawing from embodied cognition, we propose an enactive perspective of PTSD, suggesting therapies that restore the SA through direct engagement with the body and environment. We discuss the potential of agency-based therapies and innovative technologies such as gesture sonification, which translates body movements into sounds to enhance the SA. Gesture sonification offers a screen-free, noninvasive approach that could complement existing trauma-focused therapies. We emphasize the need for interdisciplinary collaboration and clinical research to further explore these approaches in preventing and treating PTSD.

Experiences of Awe Mediate Ketamine's Antidepressant Effects: Findings From a Randomized Controlled Trial in Treatment-Resistant Depression

Background

Ketamine, an NMDA receptor antagonist, provides rapid antidepressant effects. Although much research has focused on neural and molecular mechanisms of action, it is critical to also consider psychological mechanisms that may contribute to its therapeutic efficacy. The construct of an awe-inducing experience, which is a well-validated psychological phenomenon tied to emotional well-being, had not been applied previously in ketamine research.

Methods

One hundred sixteen participants with depression, 77 of whom received a ketamine infusion (0.5 mg/kg over 40 minutes) and 39 patients who received saline placebo, completed a validated measure of awe (the Awe Experience Scale [AWE-S]) at 40 minutes postinfusion. AWE-S scores were examined as potential mediators of depression outcomes (% improvement in Montgomery-Åsberg Depression Rating Scale score) at 5 postinfusion time points (24 hours and 5, 12, 21, and 30 days). Dissociative effects, measured by Clinician-Administered Dissociative States Scale scores, were tested in parallel mediation models for comparison.

Results

We found that the psychological experience of awe was strongly reported by participants during ketamine infusion, but not saline infusion, and there were significant associations between total AWE-S scores and Montgomery-Åsberg Depression Rating Scale score improvement (% change) in the ketamine arm at all 5 time points. Furthermore, at all 5 time points, total AWE-S scores statistically mediated the relationship between ketamine and Montgomery-Åsberg Depression Rating Scale scores. By contrast, Clinician-Administered Dissociative States Scale scores did not mediate outcomes at any time point.

Conclusions

Ketamine infusion strongly induced heightened feelings of awe, and these experiences consistently mediated depression outcomes over a 1- to 30-day period, unlike general dissociative side effects. The specific awe-inspiring properties of ketamine may contribute to its antidepressant effects.

Cortical thickness of the posterior cingulate cortex is associated with the ketamine-induced altered sense of self: An ultra-high field MRI study

Subanesthetic doses of ketamine induce an antidepressant effect within hours in individuals with treatment-resistant depression while it furthermore induces immediate but transient psychotomimetic effects. Among these psychotomimetic effects, an altered sense of self has specifically been associated with the antidepressant response to ketamine as well as psychedelics. However, there is plenty of variation in the extent of the drug-induced altered sense of self experience that might be explained by differences in basal morphological characteristics, such as cortical thickness. Regions that have been previously associated with a psychedelics-induced sense of self and with ketamine's mechanism of action, are the posterior cingulate cortex (PCC) and the pregenual anterior cingulate cortex (pgACC). In this randomized, placebo-controlled, double-blind cross-over magnetic resonance imaging study, thirty-five healthy male participants (mean age ± standard deviation (SD) = 25.1 ± 4.2 years) were scanned at 7 T. We investigated whether the cortical thickness of two DMN regions, the PCC and the pgACC, are associated with disembodiment and experience of unity scores, which were used to index the ketamine-induced altered sense of self. We observed a negative correlation between the PCC cortical thickness and the disembodiment scores (R = -0.54, p < 0.001). In contrast, no significant association was found between the pgACC cortical thickness and the ketamine-induced altered sense of self. In the context of the existing literature, our findings highlight the importance of the PCC as a structure involved in the mechanism of ketamine-induced altered sense of self that seems to be shared with different antidepressant agents with psychotomimetic effects operating on different classes of transmitter systems.

Acute Dissociation and Ketamine's Antidepressant and Anti-Suicidal Ideation Effects in a Midazolam-Controlled Trial

OBJECTIVE

We sought to explore relationships of acute dissociative effects of intravenous ketamine with change in depression and suicidal ideation and with plasma metabolite levels in a randomized, midazolam-controlled trial.

METHODS

Data from a completed trial in suicidal, depressed participants (n = 40) randomly assigned to ketamine was used to examine relationships between ketamine treatment-emergent dissociative and psychotomimetic symptoms with pre/post-infusion changes in suicidal ideation and depression severity. Nonparametric correlational statistics were used. These methods were also used to explore associations between dissociative or psychotomimetic symptoms and blood levels of ketamine and metabolites in a subset of participants (n = 28) who provided blood samples immediately post-infusion.

RESULTS

Neither acute dissociative nor psychotomimetic effects of ketamine were associated with changes in suicidal ideation or depressive symptoms from pre- to post-infusion. Norketamine had a trend-level, moderate inverse correlation with dissociative symptoms on Day 1 post-injection (P  = .064; P =.013 removing 1 outlier). Dehydronorketamine correlated with Clinician-Administered Dissociative States Scale scores at 40 minutes (P = .034), 230 minutes (P = .014), and Day 1 (P = .012).

CONCLUSION

We did not find evidence that ketamine's acute, transient dissociative, or psychotomimetic effects are associated with its antidepressant or anti-suicidal ideation actions. The correlation of higher plasma norketamine with lower dissociative symptoms on Day 1 post-treatment suggests dissociation may be more an effect of the parent drug.

Modeling the structural relationships between trauma exposure with substance use tendency, depression symptoms, and suicidal thoughts in individuals with earthquake trauma experience: the mediatory role of peritraumatic dissociation and experiential avoidance

BACKGROUND

Despite the fact that studies indicate that earthquake trauma is associated with numerous psychological consequences, the mediating mechanisms leading to these outcomes have not been well-studied. Therefore, this study investigates the relationship between trauma exposure with substance use tendency, depression, and suicidal thoughts, with the mediating role of peritraumatic dissociation and experiential avoidance.

METHODS

The descriptive-correlational approach was employed in this study. The participants were people who had experienced the Kermanshah earthquake in 2017. A total of 324 people were selected by convenient sampling method. The Traumatic Exposure Severity Scale, the Peritraumatic Dissociative Experiences Questionnaire, the Acceptance and Action Questionnaire, the Iranian Addiction Potential Scale, Beck's Depression Inventory [BDI-II], and Beck's Suicidal Thoughts Scale were used to collect data. The gathered data was analyzed‌ using structural equation modeling in ‌SPSS Ver. 24 and LISREL Ver. 24.

RESULTS

The study findings indicated that the intensity of the trauma exposure is directly and significantly associated with depression symptoms, peritraumatic dissociation, and experiential avoidance. The severity of exposure to trauma had a significant indirect effect on the tendency to use substances through experiential avoidance. This is while the severity of the trauma experience did not directly correlate with substance use and suicidal thoughts. In addition, peritraumatic dissociation did not act as a mediator in the relationship between the severity of trauma exposure with substance use, depression, and suicidal thoughts.

CONCLUSIONS

The severity of exposure to the earthquake was associated with symptoms of depression and these findings indicate the importance of experiential avoidance in predicting the tendency to use drugs. Hence, it is essential to design and implement psychological interventions that target experiential avoidance to prevent drug use tendencies and to establish policies that lower depression symptoms following natural disasters.

Are "mystical experiences" essential for antidepressant actions of ketamine and the classic psychedelics?

The growing interest in the rapid and sustained antidepressant effects of the dissociative anesthetic ketamine and classic psychedelics, such as psilocybin, is remarkable. However, both ketamine and psychedelics are known to induce acute mystical experiences; ketamine can cause dissociative symptoms such as out-of-body experience, while psychedelics typically bring about hallucinogenic experiences, like a profound sense of unity with the universe or nature. The role of these mystical experiences in enhancing the antidepressant outcomes for patients with depression is currently an area of ongoing investigation and debate. Clinical studies have shown that the dissociative symptoms following the administration of ketamine or (S)-ketamine (esketamine) are not directly linked to their antidepressant properties. In contrast, the antidepressant potential of (R)-ketamine (arketamine), thought to lack dissociative side effects, has yet to be conclusively proven in large-scale clinical trials. Moreover, although the activation of the serotonin 5-HT2A receptor is crucial for the hallucinogenic effects of psychedelics in humans, its precise role in their antidepressant action is still under discussion. This article explores the importance of mystical experiences in enhancing the antidepressant efficacy of both ketamine and classic psychedelics.

Ketamine-assisted psychotherapy, psychedelic methodologies, and the impregnable value of the subjective-a new and evolving approach

Psychiatry is in a growth phase in which several psychedelic medicines have entered its arena with great promise. Of these, presently, ketamine is the only medicine that may be legally prescribed. We hypothesize that at subanesthetic doses, ketamine produces a unique spectrum of altered states, ranging from psychoactive to deep ego-dissolving experiences, that are intrinsic to ketamine's therapeutic effects. When these experiences are embedded in a therapeutic relationship-a setting-that fosters an amplification of the recipient's subjective consciousness, personal growth, inner healing, greater clarity, and better relationships may well ensue. While much of the literature on ketamine labels its dissociative effects as 'side effects', alteration of consciousness is a component and unavoidable 'effect' of its therapeutic impact. From its inception in the clinical trials of the 1960s, ketamine was recognized for producing dissociative, psychedelic effects on consciousness in subjects as they emerged from ketamine-induced anesthesia. Unanticipated and unintegrated, these experiences of 'emergence phenomena' were felt to be disturbing. Accordingly, such experiences have been typically labeled as dissociative side effects. However, in a conducive set and settings, these experiences have been demonstrated to be of positive use in psychiatry and psychotherapy, providing a time-out from usual states of mind to facilitate a reshaping of self-experience along with symptomatic relief. In this way, ketamine-assisted psychotherapy (KAP) offers a new potential in psychiatry and psychotherapy that is powerfully valanced toward recognizing experience, individuality, and imagination. Essential to a successful therapeutic experience and outcome with KAP is close attention to the subjective experience, its expression by the recipient and integration of the ketamine experience as a healing opportunity.

Effects of a dissociative drug on fronto-limbic resting-state functional connectivity in individuals with posttraumatic stress disorder: a randomized controlled pilot study

RATIONALE

A subanesthetic dose of ketamine, a non-competitive N-methyl-D-aspartate glutamate receptor (NMDAR) antagonist, elicits dissociation in individuals with posttraumatic stress disorder (PTSD), who also often suffer from chronic dissociative symptoms in daily life. These debilitating symptoms have not only been linked to worse PTSD trajectories, but also to increased resting-state functional connectivity (RSFC) between medial prefrontal cortex (mPFC) and amygdala, supporting the conceptualization of dissociation as emotion overmodulation. Yet, as studies were observational, causal evidence is lacking.

OBJECTIVES

The present randomized controlled pilot study examines the effect of ketamine, a dissociative drug, on RSFC between mPFC subregions and amygdala in individuals with PTSD.

METHODS

Twenty-six individuals with PTSD received either ketamine (0.5mg/kg; n = 12) or the control drug midazolam (0.045mg/kg; n = 14) during functional magnetic resonance imaging (fMRI). RSFC between amygdala and mPFC subregions, i.e., ventromedial PFC (vmPFC), dorsomedial PFC (dmPFC) and anterior-medial PFC (amPFC), was assessed at baseline and during intravenous drug infusion.

RESULTS

Contrary to pre-registered predictions, ketamine did not promote a greater increase in RSFC between amygdala and mPFC subregions from baseline to infusion compared to midazolam. Instead, ketamine elicited a stronger transient decrease in vmPFC-amygdala RSFC compared to midazolam.

CONCLUSIONS

A dissociative drug did not increase fronto-limbic RSFC in individuals with PTSD. These preliminary experimental findings contrast with prior correlative findings and call for further exploration and, potentially, a more differentiated view on the neurobiological underpinning of dissociative phenomena in PTSD.

EEG-vigilance regulation is associated with and predicts ketamine response in major depressive disorder

Ketamine offers promising new therapeutic options for difficult-to-treat depression. The efficacy of treatment response, including ketamine, has been intricately linked to EEG measures of vigilance. This research investigated the interplay between intravenous ketamine and alterations in brain arousal, quantified through EEG vigilance assessments in two distinct cohorts of depressed patients (original dataset: n = 24; testing dataset: n = 24). Clinical response was defined as a decrease from baseline of >33% on the Montgomery-Åsberg Depression Rating Scale (MADRS) 24 h after infusion. EEG recordings were obtained pre-, start-, end- and 24 h post- infusion, and the resting EEG was automatically scored using the Vigilance Algorithm Leipzig (VIGALL). Relative to placebo (sodium chloride 0.9%), ketamine increased the amount of low-vigilance stage B1 at end-infusion. This increase in B1 was positively related to serum concentrations of ketamine, but not to norketamine, and was independent of clinical response. In contrast, treatment responders showed a distinct EEG pattern characterized by a decrease in high-vigilance stage A1 and an increase in low-vigilance B2/3, regardless of whether placebo or ketamine had been given. Furthermore, pretreatment EEG differed between responders and non-responders with responders showing a higher percentage of stage A1 (53% vs. 21%). The logistic regression fitted on the percent of A1 stages was able to predict treatment outcomes in the testing dataset with an area under the ROC curve of 0.7. Ketamine affects EEG vigilance in a distinct pattern observed only in responders. Consequently, the percentage of pretreatment stage A1 shows significant potential as a predictive biomarker of treatment response.Clinical Trials Registration: https://www.clinicaltrialsregister.eu/ctr-search/trial/2013-000952-17/CZ Registration number: EudraCT Number: 2013-000952-17.

Listening to music during intranasal (es)ketamine therapy in patients with treatment-resistant depression correlates with better tolerability and reduced anxiety

Background

Although the effectiveness of (es)ketamine for therapy-resistant depression (TRD) has been established, potential treatment-limiting factors include side effects like dissociation, anxiety, or elevated blood pressure. Music can reduce stress and negative emotions as anxiety. This study aimed to investigate the impact of listening to music during intranasal (es)ketamine administration on both tolerability and efficacy.

Methods

Records of 494 sessions (of 37 patients) with intranasal (es)ketamine administration, each containing data of blood pressure measurements, DSS-IV (dissociation symptoms scale-IV), anxiety and euphoria analogue scale, MADRS (Montgomery-Åsberg Depression Rating Scale) and BDI (Beck's Depression Inventory) were evaluated.

Results

The between-group analysis, comparing participants who listened to music with those who did not, revealed significant differences in the administered dose (p-value: 0.003, mean: 131.5 mg with music vs. 116.7 mg without music), scores on the DSS Item 1 (p-value: 0.005, mean: 3 points vs. 2.4 points), levels of anxiety (p-value: <0.001, mean: 0.4 points vs. 1.4 points), and measurements of maximal systolic blood pressure after administration (p-value: 0.017, mean: 137.9 mmHg vs. 140.3 mmHg). Listening to music had no impact on the MARDS-change score between the sessions.

Limitations

Key limitations include a non-randomized naturalistic design and the non-standardized selection of music, which was based on individual patient preferences.

Conclusion

Listening to music during intranasal (es)ketamine therapy appears to be linked to reduced anxiety and lower blood pressure, stable or increased dissociation levels, and improved tolerance for higher doses. These findings could potentially contribute to the optimization of (es)ketamine therapy, both in terms of treatment efficacy and managing side effects.

The Psychedelic Future of Post-Traumatic Stress Disorder Treatment

Post-traumatic stress disorder (PTSD) is a mental health condition that can occur following exposure to a traumatic experience. An estimated 12 million U.S. adults are presently affected by this disorder. Current treatments include psychological therapies (e.g., exposure-based interventions) and pharmacological treatments (e.g., selective serotonin reuptake inhibitors (SSRIs)). However, a significant proportion of patients receiving standard-of-care therapies for PTSD remain symptomatic, and new approaches for this and other trauma-related mental health conditions are greatly needed. Psychedelic compounds that alter cognition, perception, and mood are currently being examined for their efficacy in treating PTSD despite their current status as Drug Enforcement Administration (DEA)- scheduled substances. Initial clinical trials have demonstrated the potential value of psychedelicassisted therapy to treat PTSD and other psychiatric disorders. In this comprehensive review, we summarize the state of the science of PTSD clinical care, including current treatments and their shortcomings. We review clinical studies of psychedelic interventions to treat PTSD, trauma-related disorders, and common comorbidities. The classic psychedelics psilocybin, lysergic acid diethylamide (LSD), and N,N-dimethyltryptamine (DMT) and DMT-containing ayahuasca, as well as the entactogen 3,4-methylenedioxymethamphetamine (MDMA) and the dissociative anesthetic ketamine, are reviewed. For each drug, we present the history of use, psychological and somatic effects, pharmacology, and safety profile. The rationale and proposed mechanisms for use in treating PTSD and traumarelated disorders are discussed. This review concludes with an in-depth consideration of future directions for the psychiatric applications of psychedelics to maximize therapeutic benefit and minimize risk in individuals and communities impacted by trauma-related conditions.

[Ketamine in antidepressant treatment: a revolution?]

Thirty percent of depressed patients are treatment resistant (TRD) suggesting the need of new therapeutic strategy. Recently, it has been shown that ketamine, an anesthetic agent with dissociative effects, has potent and rapid antidepressant properties. Ketamine is a ionotropic glutamatergic NMDA antagonist that inhibits gabaergic neurons. Its antidepressant effect peaks at 24 h post-treatment. Several meta-analyses of placebo randomized clinical trials emphasized its efficacy. More recently, a meta-analysis showed its efficiency in real-world population of TRD patients. Although there is no clear biological or clinical predictors of response or remission to ketamine, patients with high level of resistance were found to remit less often. Restoring both the optimism bias and the asymmetry in belief updating mediates the antidepressant ketamine's effect. Consistent with predictive bayesian model and terror management theory, this suggests that dissociation induced by ketamine may contribute to its clinical antidepressant action. Although increasing access to ketamine and esketamine is welcome, legitimate concerns have been raised with respect to long-term safety and abuse risk.

Storm on predictive brain: A neurocomputational account of ketamine antidepressant effect

For the past decade, ketamine, an N-methyl-D-aspartate receptor (NMDAr) antagonist, has been considered a promising treatment for major depressive disorder (MDD). Unlike the delayed effect of monoaminergic treatment, ketamine may produce fast-acting antidepressant effects hours after a single administration at subanesthetic dose. Along with these antidepressant effects, it may also induce transient dissociative (disturbing of the sense of self and reality) symptoms during acute administration which resolve within hours. To understand ketamine's rapid-acting antidepressant effect, several biological hypotheses have been explored, but despite these promising avenues, there is a lack of model to understand the timeframe of antidepressant and dissociative effects of ketamine. In this article, we propose a neurocomputational account of ketamine's antidepressant and dissociative effects based on the Predictive Processing (PP) theory, a framework for cognitive and sensory processing. PP theory suggests that the brain produces top-down predictions to process incoming sensory signals, and generates bottom-up prediction errors (PEs) which are then used to update predictions. This iterative dynamic neural process would relies on N-methyl-D-aspartate (NMDAr) and α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic receptors (AMPAr), two major component of the glutamatergic signaling. Furthermore, it has been suggested that MDD is characterized by over-rigid predictions which cannot be updated by the PEs, leading to miscalibration of hierarchical inference and self-reinforcing negative feedback loops. Based on former empirical studies using behavioral paradigms, neurophysiological recordings, and computational modeling, we suggest that ketamine impairs top-down predictions by blocking NMDA receptors, and enhances presynaptic glutamate release and PEs, producing transient dissociative symptoms and fast-acting antidepressant effect in hours following acute administration. Moreover, we present data showing that ketamine may enhance a delayed neural plasticity pathways through AMPAr potentiation, triggering a prolonged antidepressant effect up to seven days for unique administration. Taken together, the two sides of antidepressant effects with distinct timeframe could constitute the keystone of antidepressant properties of ketamine. These PP disturbances may also participate to a ketamine-induced time window of mental flexibility, which can be used to improve the psychotherapeutic process. Finally, these proposals could be used as a theoretical framework for future research into fast-acting antidepressants, and combination with existing antidepressant and psychotherapy.

The 5-HT1A receptor biased agonists, NLX-204 and NLX-101, display ketamine-like RAAD and anti-TRD activities in rat CMS models

OBJECTIVES

NLX-101 and NLX-204 are highly selective serotonin 5-HT1A 'biased' agonists, displaying potent and efficacious antidepressant-like activity upon acute administration in models such as the forced swim test.

METHODS

we compared the effects of repeated administration of NLX-101, NLX-204 and ketamine in the chronic mild stress (CMS) model of depression, considered to have high translational potential, on sucrose consumption (anhedonia measure), novel object recognition (NOR; working memory measure) and elevated plus maze (EPM; anxiety measure) in male Wistar and Wistar-Kyoto rats (the latter being resistant to classical antidepressants).

RESULTS

in Wistar rats, NLX-204 and NLX-101 (0.08-0.16 mg/kg i.p.), like ketamine (10 mg/kg i.p.) dose-dependently reversed CMS-induced sucrose intake deficit from treatment Day 1, with nearly full reversal observed at the higher dose at Days 8 and 15. These effects persisted for 3 weeks following treatment cessation. In the NOR test, both doses of NLX-101/NLX-204, and ketamine, rescued the deficit in discrimination index caused by CMS on Days 3 and 17; all three compounds increased time spent in open arms (EPM) but only NLX-204 achieved statistical significance on Days 2 and 16. In Wistar-Kyoto rats, all 3 compounds were also active in the sucrose test and, to a lesser extent, in the NOR and EPM. In non-stressed rats (both strains), the three compounds produced no significant effects in all tests.

CONCLUSIONS

these observations further strengthen the hypothesis that biased agonism at 5-HT1A receptors constitutes a promising strategy to achieve rapid-acting/sustained antidepressant effects combined with activity against TRD, in addition to providing beneficial effects against memory deficit and anxiety in depressed patients.

Case report: Maintaining altered states of consciousness over repeated ketamine infusions may be key to facilitate long-lasting antidepressant effects: some initial lessons from a personalized-dosing single-case study

Background

The interest in psychoactive agents for treating mental disorders has gathered a growing body of scientific interest. However, research on the relationship between altered states of consciousness (ASCs) and ketamine's antidepressant properties is still limited. Likewise, approaches to sustain early treatment success for the long-term are needed. Taking both aspects into account, the question arises whether the persistence of recurrent ASCs during the subsequent infusion sessions is crucial for the preservation of antidepressant effects during prolonged continued ketamine therapy.

Aim

In this case study we explored whether recurrent ASC experiences across a large number of infusions are associated with improved antidepressant effects in a single case study.

Methods

A 62-year-old patient with treatment-resistant depression, who has been suffering from depressive episodes for over 20 years, was observed for 12 consecutive infusions across 16 weeks. ASCs during ketamine sessions were measured with the 5D-ASC, and pre/post-infusion depression scores with the BDI-II questionnaire. To emphasize psychoactive experiences a personalized antidepressant dose regimen was used.

Results

We found a strong correlation between the experienced ASCs during ketamine infusions and the antidepressant effect: the stronger the ASCs overall, the stronger the resulting antidepressant effect. This correlation was consistently observed throughout the infusion series, independent of the number of ketamine sessions completed before. However, despite a personalized dose regimen, neither peri-infusion ASCs nor antidepressant effects could be established on a regular basis, leading overall to no improvement in treatment outcome.

Conclusion

Maintaining psychoactive effects over repeated ketamine infusions may be key to facilitate long-lasting antidepressant effects. However, for some depressed individuals maintenance of antidepressant effects and/or peri-infusion ASCs might not be achieved, even when personalized dosing is used.

Ketamine's acute effects on negative brain states are mediated through distinct altered states of consciousness in humans

Ketamine commonly and rapidly induces dissociative and other altered states of consciousness (ASCs) in humans. However, the neural mechanisms that contribute to these experiences remain unknown. We used functional neuroimaging to engage key regions of the brain's affective circuits during acute ketamine-induced ASCs within a randomized, multi-modal, placebo-controlled design examining placebo, 0.05 mg/kg ketamine, and 0.5 mg/kg ketamine in nonclinical adult participants (NCT03475277). Licensed clinicians monitored infusions for safety. Linear mixed effects models, analysis of variance, t-tests, and mediation models were used for statistical analyses. Our design enabled us to test our pre-specified primary and secondary endpoints, which were met: effects of ketamine across dose conditions on (1) emotional task-evoked brain activity, and (2) sub-components of dissociation and other ASCs. With this design, we also could disentangle which ketamine-induced affective brain states are dependent upon specific aspects of ASCs. Differently valenced ketamine-induced ASCs mediated opposing effects on right anterior insula activity. Participants experiencing relatively higher depersonalization induced by 0.5 mg/kg of ketamine showed relief from negative brain states (reduced task-evoked right anterior insula activity, 0.39 SD). In contrast, participants experiencing dissociative amnesia showed an exacerbation of insula activity (0.32 SD). These results in nonclinical participants may shed light on the mechanisms by which specific dissociative states predict response to ketamine in depressed individuals.

Phenomenology and therapeutic potential of patient experiences during oral esketamine treatment for treatment-resistant depression: an interpretative phenomenological study

BACKGROUND

Ketamine and its enantiomers are widely researched and increasingly used to treat mental disorders, especially treatment-resistant depression. The phenomenology of ketamine-induced experiences and their relation to its psychotherapeutic potential have not yet been systematically investigated.

AIMS

To describe the phenomenology of patient experiences during oral esketamine treatment for treatment-resistant depression (TRD) and to explore the potential therapeutic relevance of these experiences.

METHODS

In-depth interviews were conducted with 17 patients after a 6-week, twice-weekly 'off label' generic oral esketamine (0.5-3.0mg/kg) treatment program. Interviews explored participants' perspectives, expectations, and experiences with oral esketamine treatment. Audio interviews were transcribed and analyzed using an Interpretative Phenomenological Analysis (IPA) framework.

RESULTS

The effects of ketamine were highly variable, and psychological distress was common in most patients. Key themes included (a) perceptual effects (auditory, visual, proprioceptive), (b) detachment (from body, self, emotions, and the world), (c) stillness and openness, (d) mystical-type effects (transcendence, relativeness, spirituality), and (e) fear and anxiety. Key themes related to post-session reports included (a) feeling hungover and fatigued, and (b) lifting the blanket: neutralizing mood effects.

CONCLUSION

Patients reported several esketamine effects with psychotherapeutic potential, such as increased openness, detachment, an interruption of negativity, and mystical-type experiences. These experiences deserve to be explored further to enhance treatment outcomes in patients with TRD. Given the frequency and severity of the perceived distress, we identify a need for additional support in all stages of esketamine treatment.

[Combination of ketamine and esketamine with Exposure and Response Prevention (ERP) therapy for Obsessive-Compulsive Disorder]

Obsessive-Compulsive Disorder (OCD), characterized by the combination of obsession and compulsion, is a clinical and therapeutic challenge. Many patients with OCD do not respond to first-line treatments such as serotonin selective reuptake inhibitors (SSRIs) and exposure and response prevention psychotherapy (ERP). For these resistant patients, some preliminary studies have shown that ketamine, a non-selective glutamatergic NMDA receptors antagonist, could improve the obsessive symptoms. A number of these studies have also suggested that the combination of ketamine with ERP psychotherapy may jointly potentiate the effectiveness of ketamine and ERP. In this paper, we present the existing data on the combined use of ketamine with ERP psychotherapy for OCD. We suggest that modulation of NMDA receptor activity and glutamatergic signaling by ketamine may promote the therapeutic mechanisms involved in ERP such as fear extinction and brain plasticity mechanisms. Finally, we propose a ketamine-augmented ERP psychotherapy (KAP-ERP) protocol in OCD, and we present the limitations associated with its application in clinical practice.

Reconsidering "dissociation" as a predictor of antidepressant efficacy for esketamine

RATIONALE

The relationship between subjective drug experience and antidepressant outcomes for ketamine derivatives is poorly understood but of high clinical relevance. Esketamine is the patented (S)-enantiomer of ketamine and has regulatory approval for psychiatric applications.

OBJECTIVES

We examined the relationship between acute dissociation, as measured by the Clinician-Administered Dissociative States Scale (CADSS), and antidepressant efficacy, as measured by the Montgomery-Åsberg Depression Rating Scale (MADRS), for esketamine across the 4-week induction phase of treatment.

METHODS

This post hoc analysis combined data (N = 576) from the TRANSFORM-1 and TRANSFORM-2 clinical trials of esketamine for treatment-resistant depression. Linear mixed models were performed using total MADRS score as the outcome variable with the following independent variables: baseline MADRS score, treatment condition × time interaction, and CADSS × time interaction. To assess whether initial dissociation predicted rapid antidepressant benefit with esketamine, a separately planned regression was performed with day 2 MADRS as the outcome variable with the following dependent variables: baseline MADRS, treatment condition, and day 1 CADSS.

RESULTS

The linear mixed model did not show any effect of a CADSS × time interaction (p = 0.7). Looking solely at the effect of day 1 CADSS on day 2 MADRS revealed that each additional CADSS point was associated with a - .04 [95% CI - .08, - .002] (p = .04) decrease in MADRS score.

CONCLUSIONS

We found no evidence of a clinically significant positive or negative association between dissociation and antidepressant effect for esketamine. Our findings suggest that subsequent inquiry in this area will benefit from improved characterization of drug experiences relevant to therapeutic outcomes.

Adverse Events and Measurement of Dissociation After the First Dose of Esketamine in Patients With TRD

BACKGROUND

"Dissociation" comprises distinct phenomena, some of which are associated with esketamine treatment and some may overlap with positive symptoms of psychosis. Relationships between dissociation and psychotic symptoms assessed by -clinician report vs conventional rating scales were investigated in a post hoc analysis of data from the initial treatment session in an -open-label, -long-term safety, phase 3 study of esketamine plus a newly initiated oral antidepressant in patients with treatment-resistant depression.

METHODS

Adverse events of dissociation or psychosis were examined via investigator report and the Clinician Administered Dissociative States Scale (CADSS) and Brief Psychiatric Rating Scale-Plus, respectively, 40 minutes post first esketamine dose. The range of CADSS total scores associated with investigator-reported severity of dissociation was determined by equipercentile linking. Logistic regression models and receiver operating curve analysis explored the CADSS cutoff point for determining presence/absence of dissociation. Frequency of response to specific CADSS items was examined to investigate qualitative differences in the pattern of symptoms reported across investigator-reported levels of adverse event severity.

RESULTS

Dissociation was reported as an adverse event in 14.3% (109/764) of patients. Severity of most CADSS items increased with the severity of investigator-reported dissociation. No CADSS cutoff point discriminated well between the presence and absence of dissociation events. Hallucinations were reported as adverse events in 5 patients; none reported delusions.

CONCLUSIONS

CADSS scores and severity of dissociation adverse events move generally in the same direction; however, there is substantial variability in this relationship. No signature profile of dissociative experiences was revealed, and psychotic symptoms were uncommon.

TRIAL REGISTRATION

Clinical Trials.gov identifier: NCT02497287.

Association of the delayed changes in glutamate levels and functional connectivity with the immediate network effects of S-ketamine

Ketamine shows rapid antidepressant effects peaking 24 h after administration. The antidepressant effects may occur through changes in glutamatergic metabolite levels and resting-state functional connectivity (rsFC) within the default mode network (DMN). A multistage drug effect of ketamine has been suggested, inducing acute effects on dysfunctional network configuration and delayed effects on homeostatic synaptic plasticity. Whether the DMN-centered delayed antidepressant-related changes are associated with the immediate changes remains unknown. Thirty-five healthy male participants (25.1 ± 4.2 years) underwent 7 T magnetic resonance spectroscopy (MRS) and resting-state functional magnetic resonance imaging (rsfMRI) before, during, and 24 h after a single S-ketamine or placebo infusion. Changes in glutamatergic measures and rsFC in the DMN node pregenual anterior cingulate cortex (pgACC) were examined. A delayed rsFC decrease of the pgACC to inferior parietal lobe (family-wise error corrected p (p_FWEc) = 0.018) and dorsolateral prefrontal cortex (PFC; p_FWEc = 0.002) was detected that was preceded by an immediate rsFC increase of the pgACC to medial PFC (p_FWEc < 0.001) and dorsomedial PFC (p_FWEc = 0.005). Additionally, the immediate rsFC reconfigurations correlated with the delayed pgACC glutamate (Glu) level increase (p = 0.024) after 24 h at trend level (p = 0.067). Baseline measures of rsFC and MRS were furthermore associated with the magnitude of the respective delayed changes (p's < 0.05). In contrast, the delayed changes were not associated with acute psychotomimetic side effects or plasma concentrations of ketamine and its metabolites. This multimodal study suggests an association between immediate S-ketamine-induced network effects and delayed brain changes at a time point relevant in its clinical context.

The Relationship Between Acute Dissociative Effects Induced by Ketamine and Treatment Response in Adolescent Patients with Treatment-Resistant Depression

Objective: Ketamine has proven effective as a rapid-acting antidepressant agent. Several adult studies have investigated the association between ketamine's acute dissociative effects and depression response, but no studies have examined the association in adolescents with treatment-resistant depression (TRD). Methods: We conducted a secondary data analysis of 16 adolescent participants who participated in a randomized, single-dose, midazolam-controlled crossover trial of ketamine in adolescents with depression. We examined the association between the acute dissociative symptoms (measured at 60 minutes following start of infusion using the Clinician-Administered Dissociative States Scale [CADSS], and its three subscales: depersonalization, derealization, amnesia) and response and depression symptom improvement at 1'day (using the Montgomery-Åsberg Depression Rating Scale). Results: Within the ketamine group, there were no significant associations between dissociation symptoms or CADSS subscale scores and magnitude of depression symptom improvement or likelihood of ketamine response. When receiving midazolam, there was no significant association between overall dissociation symptoms and magnitude or likelihood of response of depressive symptoms. Higher levels of symptoms on the 'depersonalization' CADSS subscale when receiving midazolam were associated with less improvement in depression symptoms at 1 day following infusion. Conclusions: In contrast to some adult literature, the current data do not show a relationship between acute dissociative effects and antidepressant response to ketamine in pediatric patients with TRD. Interpretation may be limited by the small sample size, reducing the power to detect small or medium associations. Future research should utilize larger samples to more definitively measure the magnitude of association between acute dissociative symptoms and later antidepressant response to ketamine and to assess the relationship to trial design (e.g., crossover vs. parallel trial, comparison condition utilized and number of infusions) within both adult and pediatric populations. ClinicalTrials.gov identifier: NCT02579928.

Pedunculopontine-induced cortical decoupling as the neurophysiological locus of dissociation

Mounting evidence suggests an association between aberrant sleep phenomena and dissociative experiences. However, no wake-sleep boundary theory provides a compelling explanation of dissociation or specifies its physiological substrates. We present a theoretical account of dissociation that integrates theories and empirical results from multiple lines of research concerning the domain of dissociation and the regulation of rapid eye movement (REM) sleep. This theory posits that individual differences in the circuitry governing the REM sleep promoting Pedunculopontine Nucleus and Laterodorsal Tegmental Nucleus determine the degree of similarity in the cortical connectivity profiles of wakefulness and REM sleep. We propose that a latent trait characterized by elevated dissociative experiences emerges from the decoupling of frontal executive regions due to a REM sleep-like aminergic/cholinergic balance. The Pedunculopontine-Induced Cortical Decoupling Account of Dissociation (PICDAD) suggests multiple fruitful lines of inquiry and provides novel insights. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Ketamine and its metabolites: Potential as novel treatments for depression

Depression is a well-known serious mental illness, and the onset of treatment using traditional antidepressants is frequently delayed by several weeks. Moreover, numerous patients with depression fail to respond to therapy. One major breakthrough in antidepressant therapy is that subanesthetic ketamine doses can rapidly alleviate depressive symptoms within hours of administering a single dose, even in treatment-resistant patients. However, specific mechanisms through which ketamine exerts its antidepressant effects remain elusive, leading to concerns regarding its rapid and long-lasting antidepressant effects. N-methyl-d-aspartate receptor (NMDAR) antagonists like ketamine are reportedly associated with serious side effects, such as dissociative symptoms, cognitive impairment, and abuse potential, limiting the large-scale clinical use of ketamine as an antidepressant. Herein, we reviewed the pharmacological properties of ketamine and the mechanisms of action underlying the rapid antidepressant efficacy, including the disinhibition hypothesis and synaptogenesis, along with common downstream effector pathways such as enhanced brain-derived neurotrophic factor and tropomyosin-related kinase B signaling, activation of the mechanistic target of rapamycin complex 1 and transforming growth factor β1. We focused on evidence supporting the relevance of these potential mechanisms of ketamine and its metabolites in mediating the clinical efficacy of the drug. Given its reported antidepressant efficacy in preclinical studies and limited undesirable adverse effects, (R)-ketamine may be a safer, more controllable, rapid antidepressant. Overall, understanding the potential mechanisms of action of ketamine and its metabolites in combination with pharmacology may help develop a new generation of rapid antidepressants that maximize antidepressant effects while avoiding unfavorable adverse effects. This article is part of the Special Issue on 'Ketamine and its Metabolites'.

Impact of Repeated Doses of Subcutaneous Esketamine on Acute Dissociative Symptoms in Treatment-Resistant Depression

BACKGROUND

Esketamine has been approved by the US Food and Drug Administration (FDA) as an adjunctive treatment for use in conjunction with an oral antidepressant for patients with treatment-resistant depression (TRD), but dissociative symptoms are common adverse effects.

METHODS

A retrospective analysis of 394 subcutaneous esketamine injections given to 70 patients with TRD that were administered once a week during a six-week trial in conjunction with oral antidepressant therapy. Doses between 0.5 to 1.0 mg/kg were administered according to the patient's response. Dissociative symptoms were assessed using the Clinician-Administered Dissociative States Scale (CADSS) 30 and 60 min after every weekly treatment (day 1, 8, 15, 22, 29 and 36).

RESULTS

Seventy patients received a total of 394 subcutaneous esketamine injections over six weeks. Over time, the evolution of CADSS scores demonstrated a significant mean difference of CADSS at 60 min post-injection (p = 0.010) throughout the six infusions. The mean CADSS scores at 60 min on day 22, 29 and 36 were similar. There were no differences between mean CADSS scores 30 min after the injections, no clinical correlation between response and dissociative symptoms, no correlation between time and demographic and clinical characteristics and no interactions between time and combined medication.

CONCLUSIONS

Our results suggest that repeated subcutaneous esketamine doses are safe and well-tolerated regarding their acute dissociative and psychotomimetic symptoms. Symptoms usually peak at 30 min and decrease at 60 min post-injection, returning to their pretreatment levels at 120 min. Dissociative symptoms do not correlate with antidepressant response.

Association between peripheral biomarkers and clinical response to IV ketamine for unipolar treatment-resistant depression: An open label study

BACKGROUND

Major Depression is the leading cause of disability worldwide. A cohort of patients do not respond adequately to available antidepressants, leading to treatment-resistant depression (TRD). We evaluated the antidepressant efficacy of an acute intravenous ketamine treatment (0.5 mg/kg) for patients with unipolar TRD, and measured peripheral blood-based biomarkers associated with response to treatment.

METHODS

Fifteen adults diagnosed with TRD completed an open label study of ten infusions of subanesthetic ketamine over four weeks. Out of fifteen patients, blood was collected from eleven patients at three timepoints to analyze peripheral biomarkers in isolated plasma, including IL-6, IL-10, TNF-α, BDNF, and irisin. Irisin analysis was completed using an ELISA assay, and the remaining biomarkers were analyzed together simultaneously using a multiplex immunoassay.

RESULTS

Repeated ketamine infusions produced a significant decrease in total average depressive symptoms (MADRS) at all timepoints. Improvements in depressive symptoms were significant at one week, and continued to significantly decrease until two weeks, where it was maintained. Ketamine was generally well tolerated, and we observed improvements in functional impairment, anhedonia, and psychiatric symptoms, with no increases in manic symptoms. Levels of BDNF throughout treatment inversely correlated to decreases in MADRS scores, and higher levels of baseline BDNF predicted mood responses at one- and four weeks.

LIMITATIONS

The study was observational and uncontrolled, with a sample size of 15. Outpatients remained on their course of medications, unless they were pharmacological agents that have previously been identified to block ketamine's effects.

CONCLUSIONS

Ketamine may be an efficacious and safe pharmacological option for the acute treatment of patients suffering from severe TRD. BDNF has the potential to function as a prognostic biomarker for predicting response to ketamine treatments.

At-home, sublingual ketamine telehealth is a safe and effective treatment for moderate to severe anxiety and depression: Findings from a large, prospective, open-label effectiveness trial

BACKGROUND

At-home Ketamine-assisted therapy (KAT) with psychosocial support and remote monitoring through telehealth platforms addresses access barriers, including the COVID-19 pandemic. Large-scale evaluation of this approach is needed for questions regarding safety and effectiveness for depression and anxiety.

METHODS

In this prospective study, a large outpatient sample received KAT over four weeks through a telehealth provider. Symptoms were assessed using the Patient Health Questionnaire (PHQ-9) for depression, and the Generalized Anxiety Disorder scale (GAD-7) for anxiety. Demographics, adverse events, and patient-reported dissociation were also analyzed. Symptom trajectories were identified using Growth Mixture Modeling, along with outcome predictors.

RESULTS

A sample of 1247 completed treatment with sufficient data, 62.8 % reported a 50 % or greater improvement on the PHQ-9, d = 1.61, and 62.9 % on the GAD-7, d = 1.56. Remission rates were 32.6 % for PHQ-9 and 31.3 % for GAD-7, with 0.9 % deteriorating on the PHQ-9, and 0.6 % on the GAD-7. Four patients left treatment early due to side effects or clinician disqualification, and two more due to adverse events. Three patient subpopulations emerged, characterized by Improvement (79.3 %), Chronic (11.4 %), and Delayed Improvement (9.3 %) for PHQ-9 and GAD-7. Endorsing side effects at Session 2 was associated with delayed symptom improvement, and Chronic patients were more likely than the other two groups to report dissociation at Session 4.

CONCLUSION

At-home KAT response and remission rates indicated rapid and significant antidepressant and anxiolytic effects. Rates were consistent with laboratory- and clinic-administered ketamine treatment. Patient screening and remote monitoring maintained low levels of adverse events. Future research should assess durability of effects.

Buddhist-like opposite diminishing and non-judging during ketamine infusion are associated with antidepressant response: an open-label personalized-dosing study

Background: Cognition that is not dominated by thinking in terms of opposites (opposite diminishing) or by making judgments (non-judging) can be found both in Buddhist/mindfulness contexts and in mental states that are fostered by dissociative psychedelics (N-methyl-D-aspartate antagonists) such as ketamine. Especially for the Buddhist/mindfulness case, both opposite diminishing and non-judging have been proposed to relate to mental well-being. Whether ketamine-occasioned opposite diminishing and/or non-judging relate to increased mental well-being in the form of antidepressant response is unknown, and was investigated in the present study.

Methods: In this open-label outpatient study, the dose level and frequency for the ketamine infusions were adjusted individually in close consultation with the patients suffering from depression with the overall goal to maximize antidepressant benefits—a novel dose regimen that we term personalized antidepressant dosing. In general, treatment started with an initial series of ketamine infusions with a dosage of 0.5 mg/kg body weight and was then adjusted (usually increased). A possible relationship between ketamine-induced antidepressant benefits and retrospectively reported peri-infusion experiences of opposite diminishing and non-judging was assessed based on a total of 45 ketamine-infusion treatment sessions from 11 different patients suffering from depression. Opposite diminishing and non-judging were measured with the two items from the Altered States of Consciousness Inventory (ASCI) that measure these concepts. Depression was measured with the Beck Depression Inventory (BDI-II).

Results: Peri-infusion experiences of both opposite diminishing and non-judging were associated with antidepressant responses confirming our hypothesis. Furthermore, opposite diminishing and non-judging were closely related to one another while relating to antidepressant response in distinguishable ways.

Conclusion: Future controlled randomized trials with dissociative and other psychedelics and with a larger number of participants are needed to establish the possible link of psychedelically induced opposite diminishing and non-judging with an antidepressant response more firmly.

The Clinician-Administered Dissociative States Scale (CADSS): Validation of the German Version

The Clinician-Administered Dissociative States Scale (CADSS) is a structured clinical interview to assess state dissociation rated by clinicians. The current study aimed to validate the German version of CADSS by comparing it to the established self-report measures for dissociation and exploring its underlying factor structure. Severity of within-session state dissociation was assessed directly following a standard psychotherapy session in a trauma-exposed patient sample (N= 105; 81.9% female). Internal consistency, convergent validity with other dissociation measures, and the factorial structure of the instrument were analyzed. The German version exhibited excellent internal consistency (Cronbach's α = .94) and correlated significantly with self-report measures of state dissociation (r = .86) and trait dissociation (r = .77) indicative of high convergent validity. Exploratory factor analysis revealed a three-factor solution with the factors (1) Depersonalization/Derealization, (2) Identity Confusion/Alteration, and (3) Amnesia. Results support the CADSS as a useful instrument to assess state dissociation, conceptualized as a multidimensional construct, in clinical practice.

Does body mass index predict response to intravenous ketamine treatment in adults with major depressive and bipolar disorder? Results from the Canadian Rapid Treatment Center of Excellence

BACKGROUND

Higher body mass index (BMI) has been found to predict greater antidepressant response to intravenous (IV) ketamine treatment. We evaluated the association between BMI and response to repeat-dose IV ketamine in patients with treatment-resistant depression (TRD).

METHODS

Adults (N = 230) with TRD received four infusions of IV ketamine at a community-based clinic. Changes in symptoms of depression (ie, Quick Inventory for Depressive Symptomatology-Self-Report 16; QIDS-SR16), suicidal ideation (SI; ie, QIDS-SR16 SI item), anxiety (ie, Generalized Anxiety Disorder-7 Scale), anhedonic severity (ie, Snaith-Hamilton Pleasure Scale), and functioning (ie, Sheehan Disability Scale) following infusions were evaluated. Participants were stratified by BMI as normal (18.0-24.9 kg/m2; n = 72), overweight (25-29.9 kg/m2; n = 76), obese I (30-34.9 kg/m2; n = 47), or obese II (≥35.0 kg/m2; n = 35).

RESULTS

Similar antidepressant effects with repeat-dose ketamine were reported between BMI groups (P = .261). In addition, categorical partial response (P = .149), response (P = .526), and remission (P = .232) rates were similar between the four BMI groups.

CONCLUSIONS

The findings are limited by the observational, open-label design of this retrospective analysis. Pretreatment BMI did not predict response to IV ketamine, which was effective regardless of BMI.

Views on Using Psychoactive Substances to Self-Manage Functional Neurological Disorder: Online Patient Survey Results

Objective: Functional neurological disorder (FND) causes a high burden of disability and distress. Although it is a common disorder, there is a pressing need for improved access to evidence-based treatments. With difficulties in finding effective treatment, some people with FND may seek alternative means of symptom relief, such as legal and illicit psychoactive substances, although the prevalence and nature of such self-management strategies are currently unclear. Additionally, psychoactive substances may represent novel treatment research opportunities, particularly for those with suboptimal improvement. The investigators examined the use of self-management techniques, as well as perspectives on novel therapies, in this patient population. Methods: An online survey was created to assess self-management strategies and views on novel treatments for FND, including psychedelic therapy. The survey was accessible for 1 month, and respondents were recruited internationally through social media and patient groups. A total of 1,048 respondents from 16 countries completed the survey. Results: Almost half (46%) of 980 respondents reported having tried legal psychoactive substances for the management of their FND symptoms and, on average, nicotine, alcohol, and cannabidiol were reported as modestly effective. Additionally, 15% of respondents reported having used illicit substances, mostly cannabis, to manage FND, with the majority reporting moderate effectiveness and experiencing no or minimal physical (90%) and psychological (95%) sequelae. Many respondents (46%) reported that they would be willing to try medically supervised psychedelic therapy (with 19% of respondents ambivalent) if it were found to be safe and effective. Conclusions: Many people with FND seek alternative means of symptom management outside usual medical care, including legal and illicit psychoactive substances. Further research exploring novel treatment options, such as psychedelics, in FND may be warranted.

Vital Sign Changes During Intravenous Ketamine Infusions for Depression: An Exploratory Study of Prognostic Indications

PURPOSE/BACKGROUND

Subanesthetic dosing of intravenous ketamine has shown to be an effective treatment for patients with major depressive disorder. It is unknown whether sympathetic response is related to treatment outcomes. The purpose of this study is to evaluate sympathetic response to ketamine infusions as it relates to treatment outcomes.

METHODS/PROCEDURES

This retrospective study examines an outpatient population diagnosed with major depressive disorder or bipolar depression treated with ketamine infusions. Patient characteristics, depressive symptoms measured with the Patient Health Questionnaire (PHQ-9), and vital signs were retrieved by chart review. Patients (n = 145) were categorized as responders (50% reduction in PHQ-9 or less than 10 on final PHQ-9) or nonresponders. Changes in vital signs were recorded during each infusion for the initiation series.

FINDINGS/RESULTS

Ketamine responders (51.7%) showed a significant greater increase in systolic blood pressure response during the first infusion when compared with nonresponders. There was no difference seen in diastolic pressure, heart rate, or rate pressure product. Changes in vital signs for subsequent infusions also did not approach significance.

IMPLICATIONS/CONCLUSIONS

Physiologic sensitivity to the effects of ketamine may predict treatment responsiveness. Blood pressure and heart rate did not always increase. Further work should examine possible influences on physiologic responses.

Long-term safety of ketamine and esketamine in treatment of depression

INTRODUCTION

Ketamine is an NMDA receptor antagonist that can produce rapid-acting antidepressant effects. Esketamine (Spravato), the S-enantiomer of racemic ketamine, was approved by the FDA for treatment-resistant depression in 2019. Here we review what is known about the long-term safety of both racemic ketamine and esketamine as therapies for psychiatric disorders.

AREAS COVERED

In this article, we conducted a safety review of ketamine and esketamine. In looking at ketamine and esketamine long-term safety effects, we considered data available from experimental studies and several phase-three clinical trials.

EXPERT OPINION

Based on available data, the most common side effects of ketamine/esketamine are generally transient, mild, and self-limited. These include dissociation, nausea, headache, elevated heart rate, and blood pressure. Treatment with esketamine may lead to an increased risk of lower urinary tract symptoms, such as dysuria or urgency. However, severe bladder pathology has not been reported among patients receiving doses of esketamine/ketamine in line with prescribing guidelines for depression. There is considerable data that ketamine at high doses can lead to long-term impairments in cognition. However, the esketamine clinical trials found that cognition generally remains stable or improves over time, suggesting that when used appropriately, there is no increased risk of cognitive impairment.

A comparison of the safety, feasibility, and tolerability of ECT and ketamine for treatment-resistant depression

INTRODUCTION

Treatment-resistant depression (TRD) is a problematic and prevalent public health and societal concern. Although electroconvulsive therapy (ECT) is the gold standard TRD intervention, the treatment evokes apprehension due to public perceptions, feasibility, and tolerability. Despite significant medical advancements, few medications have been approved by the U.S. Food and Drug Administration for TRD. In 2019, intranasal esketamine, the S-isomer of racemic ketamine, was approved for TRD, garnering significant excitement about the potential for the drug to act as an alternative treatment to ECT.

AREAS COVERED

The goal of this narrative review is to compare the safety, efficacy, and tolerability of ketamine and ECT; clarify whether ketamine is a reasonable alternative to ECT; and to facilitate improved treatment assignment for TRD. Empirical quantitative and qualitative studies and national and international guidelines these treatments are reviewed.

EXPERT OPINION

: The field awaits the results of two ongoing large comparative effectiveness trials of ECT and IV ketamine for TRD, which should help guide clinicians and patients as to the relative risk and benefit of these interventions. Over the next five years we anticipate further innovations in neuromodulation and in drug development which broadly aim to develop more tolerable versions of ECT and ketamine, respectively.

Ketamine for treatment of mood disorders and suicidality: A narrative review of recent progress

BACKGROUND

Mood disorders are a leading cause of morbidity. Many patients experience treatment-resistant depression (TRD), and suicide rates are rising. Faster-acting and more effective antidepressant medications are needed. Four decades of research has transformed the use of ketamine from an anesthetic to an outpatient treatment for major depressive disorder (MDD). Ketamine is a N-methyl-d-aspartate (NMDA) receptor antagonist and has been shown to rapidly improve mood symptoms and suicidal ideation by targeting the glutamate system directly.

METHODS

We used the PubMed database to identify relevant articles published until September 1, 2020. We focused on meta-analyses, randomized controlled trials, and original observational studies. We included relevant studies for depression, MDD, TRD, bipolar disorder, anxiety, posttraumatic stress disorder (PTSD), suicide, ketamine, and esketamine.

RESULTS

Both racemic ketamine and esketamine have been shown to rapidly treat depression and suicidality. There is evidence that ketamine can be helpful for anxiety and PTSD; however, more research is needed. Intranasal esketamine has been FDA approved to treat depression.

CONCLUSIONS

This narrative review describes the evolution of ketamine to treat mood disorders and suicidality. We provide the evidence supporting recent developments using esketamine as well as unresolved issues in the field, such as dosing and safety.

Relationship Between Dissociation and Antidepressant Effects of Esketamine Nasal Spray in Patients With Treatment-Resistant Depression

BACKGROUND

In this post-hoc analysis, data from 2 positive, pivotal, phase 3 trials of esketamine nasal spray (ESK) in treatment-resistant depression (TRD)-short-term study (TRANSFORM-2) and maintenance study (SUSTAIN-1)-were analyzed to evaluate the relationship between dissociation and antidepressant effects of ESK.

METHODS

Analysis by responder status, correlation analysis, and mediation analysis were performed to assess the relationships between peak Clinician Administered Dissociative States Scale (CADSS) scores after first (day 1) and last (day 25) ESK dose and change in Montgomery-Åsberg Depression Rating Scale (MADRS) total scores at the first (day 2) and last assessments (day 28) in TRANSFORM-2 and peak CADSS after first maintenance ESK dose and time to relapse in SUSTAIN-1 (only for mediation analysis).

RESULTS

In TRANSFORM-2, the percentage of responders (>50% reduction in MADRS) at day 2 and day 28 did not significantly differ between patients who did vs did not manifest significant dissociation (peak CADSS scores >4 or ≤4, respectively) following the first ESK dose. Spearman correlation coefficients between dissociation and depression improvement were nonsignificant and close to zero. CADSS scores did not significantly mediate the reduction in MADRS at day 2 or 28 in TRANSFORM-2 or the time to depression relapse in SUSTAIN-1. The mean difference in MADRS between ESK and active-control arms persisted beyond day 2 without significant change across time, although the mean peak CADSS scores significantly decreased across consecutive doses and fewer patients experienced significant dissociation after the last ESK dose compared with the first.

CONCLUSION

Within the dose range tested, the dissociative and antidepressant effects of ESK were not significantly correlated.

TRIAL REGISTRATION

NCT02417064 (TRANSFORM-1); NCT02418585(TRANSFORM-2); NCT02493868 (SUSTAIN-1).

The effect of sexual abuse and dissociation on suicide attempt

BACKGROUND

Suicide attempt is the most predictive risk factor of suicide. Trauma - especially sexual abuse - is a risk factor for suicide attempt and suicide. A common reaction to sexual abuse is dissociation. Higher levels of dissociation are linked to self-harm, suicide ideation, and suicide attempt, but the role of dissociation in suicidal behavior is unclear.

METHODS

In this naturalistic study, ninety-seven acute psychiatric patients with suicidal ideation, of whom 32 had experienced sexual abuse, were included. Suicidal behaviour was assessed with The Columbia suicide history form (CSHF). The Brief trauma questionnaire (BTQ) was used to identify sexual abuse. Dissociative symptoms were assessed with Dissociative experiences scale (DES).

RESULTS

Patients who had experienced sexual abuse reported higher levels of dissociation and were younger at onset of suicidal thoughts, more likely to self-harm, and more likely to have attempted suicide; and they had made more suicide attempts. Mediation analysis found dissociative experiences to significantly mediate a substantive proportion of the relationship between sexual abuse and number of suicide attempts (indirect effects = 0.17, 95% CI = 0.05, 0.28, proportion mediated = 68%). Dissociative experiences significantly mediated the role of sexual abuse as a predictor of being in the patient group with more than four suicide attempts (indirect effects = 0.11, 95% CI = 0.02, 0.19, proportion mediated = 34%).

CONCLUSION

The results illustrate the importance of assessment and treatment of sexual abuse and trauma-related symptoms such as dissociation in suicide prevention. Dissociation can be a contributing factor to why some people act on their suicidal thoughts.

Pharmacological modelling of dissociation and psychosis: an evaluation of the Clinician Administered Dissociative States Scale and Psychotomimetic States Inventory during nitrous oxide ('laughing gas')-induced anomalous states

RATIONALE

A significant obstacle to an improved understanding of pathological dissociative and psychosis-like states is the lack of readily implemented pharmacological models of these experiences. Ketamine has dissociative and psychotomimetic effects but can be difficult to use outside of medical and clinical-research facilities. Alternatively, nitrous oxide (N₂O) - like ketamine, a dissociative anaesthetic and NMDAR antagonist - has numerous properties that make it an attractive alternative for modelling dissociation and psychosis. However, development and testing of such pharmacological models relies on well-characterized measurement instruments.

OBJECTIVES

To examine the factor structures of the Clinician Administered Dissociative States Scale (CADSS) and Psychotomimetic States Inventory (PSI) administered during N₂O inhalation in healthy volunteers.

METHODS

Secondary analyses of data pooled from three previous N₂O studies with healthy volunteers.

RESULTS

Effect sizes for N₂O-induced dissociation and psychotomimesis were comparable to effects reported in experimental studies with sub-anaesthetic ketamine in healthy volunteers. Although, like ketamine, a three-factor representation of N₂O-induced dissociation was confirmed, and a more parsimonious two-factor model might be more appropriate. Bayesian exploratory factor analysis suggested that N₂O-induced psychosis-like symptoms were adequately represented by two negative and two positive symptom factors. Hierarchical cluster analysis indicated minimal item overlap between the CADSS and PSI.

CONCLUSION

N₂O and ketamine produce psychometrically similar dissociative states, although parallels in their psychosis-like effects remain to be determined. The CADSS and PSI tap largely non-overlapping experiences under N₂O and we propose the use of both measures (or similar instruments) to comprehensively assess anomalous subjective states produced by dissociative NMDAR antagonists.