Real-world effectiveness of ketamine in treatment-resistant depression: A systematic review & meta-analysis

Glutamate plus glutamine to GABA ratio as a predictor of ketamine response in treatment-resistant depression: A double-blind, randomized, open-label extension study

BACKGROUND

Approximately 30 % of patients with treatment-resistant depression (TRD) respond to ketamine; however, no replicable predictors of response have been reported. The imbalance between excitatory and inhibitory neurotransmissions may be implicated in the mechanism of action of ketamine. This study aimed to evaluate whether the ratio of glutamate and glutamine (Glx) to GABA levels at baseline in the dorsal anterior cingulate cortex (dACC) could predict ketamine response in patients with TRD.

METHOD

This exploratory study analyzed data from a double-blind randomized clinical trial with an open-label extension study (jRCTs031210124). Fifteen participants in the ketamine group and 15 of 16 participants in the placebo group received repeated intravenous ketamine during the double-blind and open-label extension periods, respectively. We measured Glx and GABA levels in the dACC before and after treatment during the double-blind period using proton magnetic resonance spectroscopy. The 17-item Hamilton Depression Rating Scale (HDRS-17) was measured for depressive symptomatology. General linear models were used to examine the relationship between baseline Glx/GABA ratio and HDRS-17 score changes.

RESULT

Changes in HDRS-17 scores (mean (±SD)) following ketamine treatment were -4.9 (6.5) and -4.9 (5.2) in the double-blind and open-label periods, respectively. A higher baseline dACC Glx/GABA ratio was correlated with greater improvement in HDRS-17 (β = -0.42, p = 0.040). In the ketamine group, a reduction in the dACC Glx/GABA ratio was correlated with greater HDRS-17 improvement (β = 0.74, p = 0.009) with no such association in the placebo group.

CONCLUSION

These results suggest that excitatory-inhibitory imbalance in the dACC may predict the efficacy of ketamine in TRD.

Advances in the study of NMDA receptors in depression pathogenesis and the antidepressant efficacy of their antagonists

N-methyl-D-aspartate receptors (NMDA receptors) play a crucial role as ionotropic glutamate receptors in regulating neuroplasticity, learning, memory, and a range of psychiatric disorders. Studies indicate that dysfunction of NMDA receptors is a key pathological mechanism in depression, where abnormal activation can result in neuronal excitotoxicity, excessive extracellular calcium ion accumulation, and disrupted neuroplasticity. As a non-competitive NMDA receptor antagonist, ketamine quickly relieves depressive symptoms by decreasing the activity of extracellular NMDA receptors and activating the mTOR signaling pathway. The treatment can improve severe depression and suicide thoughts within hours, but its potential for hallucinations, dissociative symptoms, and dependency restricts its broader application. Esketamine has demonstrated improvements in both side effects and efficacy and has received FDA approval, while other compounds with NMDA receptor modulating functions, such as memantine and rapastinel, are also showing potential in exploration. Future studies should concentrate on the molecular mechanisms of NMDA receptors, aiming to develop safer and more effective medications, and refine treatment strategies to offer personalized choices and longer-lasting efficacy for the treatment of depression.

Mapping the Use of Ketamine in Treatment-Resistant Depression and Other Psychiatric Disorders: A Scoping Review of Practice Patterns, Efficacy, and Patient Demographic Trends

BACKGROUND

Ketamine has emerged as a novel treatment for psychiatric disorders, particularly treatment-resistant depression (TRD). Although intravenous (IV) ketamine is not approved by the Food and Drug Administration (FDA) for TRD, esketamine, an FDA-approved therapeutic, has contributed to the widespread clinical use of off-label IV ketamine across the United States. This scoping review highlights significant shifts in ketamine therapy, particularly after FDA approval of esketamine, the impact of COVID-19 on treatment accessibility, and increased regulatory scrutiny from the Drug Enforcement Administration (DEA) and FDA.

AREAS OF UNCERTAINTY

What are the current practice patterns, patient demographics, and barriers to accessing ketamine for psychiatric disorders, particularly TRD?

DATA SOURCES

This scoping review focused on provider utilization patterns (including frequency of ketamine administration, provider roles, and treatment settings), preferred administration methods (IV infusions, intramuscular injections, and other routes), and patient characteristics (age, sex, socioeconomic status, and primary psychiatric diagnoses treated). The Web of Science, PubMed, CBM, MEDLINE, Cochrane Library, University Theses, and Embase databases were searched.

RESULTS

Two survey-based studies were included. IV administration was the most common method of administration reported in both studies, with alternative methods such as intramuscular and sublingual routes emerging in limited use. Patients receiving ketamine therapy were predominantly middle aged (36-64 years old), with financial barriers identified as a notable obstacle because of limited insurance coverage. Access to ketamine was limited in rural areas, illustrating the need for expanded provider networks. Private clinics exhibited greater flexibility in treatment approaches than hospital settings, which adhered to standardized protocols. The absence of long-term outcome data and variability in treatment protocols emphasize the need for standardized practices and further research.

CONCLUSIONS

This scoping review highlights the widespread use of ketamine for TRD, but reveals significant variability in practice patterns and accessibility barriers. Findings emphasize the need for standardized protocols, expanded insurance coverage, and further research to optimize the role of ketamine in psychiatric care.

Oral esketamine for patients with severe treatment-resistant depression: Effectiveness, safety, and tolerability of a six-week open-label treatment program

BACKGROUND

Oral esketamine for patients with treatment-resistant depression (TRD) could offer certain advantages over other routes, such as intravenous or intranasal, but it has not been systematically studied in a real-world setting.

AIMS

Here we present results from a relatively large naturalistic study to evaluate the effectiveness, tolerability, and safety of oral esketamine in patients with TRD.

METHODS

One hundred eighty-five adults with severe TRD (average of 8.1 antidepressant trials plus electroconvulsive therapy in 63% without beneficial outcome) received oral esketamine treatment twice-weekly for 6 weeks with individually titrated doses ranging from 0.5 to 3 mg/kg. Outcome measures included change from baseline to week 6 on the Hamilton Depression Rating Scale (HDRS17), Minimal Clinically Important Difference (MCID), response, remission, self-reported symptom improvement, functioning, and side effects.

RESULTS

Oral esketamine treatment improved depressive symptom severity on the HDRS17 from 21.2 to 15.8 (p < 0.001). MCID, response, and remission rates were 47.1%, 26.8% and 15.6% respectively. In 45.9% of participants, treatment was continued after 6 weeks to maintain initial positive effects. Side effects were reported frequently but were overall well tolerated. The drop-out rate was 7.6%. We found no significant adverse effects associated with urinary tract or cognition.

CONCLUSIONS

Repeated treatment with oral esketamine is effective in improving depressive symptom severity in highly treatment-resistant depressive patients. It is safe, well tolerated, and patient-friendly. Considering the level of treatment resistance, outcomes were in the range of studies investigating other routes of (es)ketamine administration.

Rectangular Repetitive Transcranial Magnetic Monophasic vs Biphasic Stimulation for Major Depressive Disorder: A Randomized Controlled Pilot Trial

OBJECTIVES

Biphasic sinusoidal repetitive transcranial magnetic stimulation (rTMS) is a noninvasive brain stimulation treatment that has been approved by the US Food and Drug Administration for treatment-resistant depression (TRD). Recent advances suggest that standard rTMS may be improved by altering the pulse shape; however, there is a paucity of research investigating pulse shape, owing primarily to the technologic limitations of currently available devices. This pilot study examined the feasibility, tolerability, and preliminary efficacy of biphasic and monophasic rectangular rTMS for TRD.

MATERIAL AND METHODS

Twenty adult participants with TRD received randomized biphasic and monophasic rectangular rTMS; 30 rectangular rTMS sessions (3000 pulses per session) were delivered as daily sessions over six weeks at 120% resting motor threshold. Neuropsychologic testing was conducted before and after the six-week treatment course, and at one, four, and 12 weeks after treatment.

RESULTS

Two participants withdrew, leaving a final sample size of 18. Both monophasic and biphasic rTMS protocols significantly reduced depressive symptoms in patients with TRD without any significant side effects. In contrast to our hypothesis, there were no differences between the two treatment groups in terms of change in depressive scores, response rates, or remission rates.

CONCLUSIONS

Findings from this pilot study revealed that both biphasic and monophasic rectangular rTMS are safe and well-tolerated. Larger, double-blind sham-controlled trials are needed to confirm the response and remission rates observed in this study.

CLINICAL TRIAL REGISTRATION

The Clinicaltrials.gov registration number for the study is NCT02667041.

Innovative approaches in the treatment-resistant depression: exploring different therapeutic pathways

Treatment-resistant depression (TRD) remains a vital challenge in psychiatry, affecting a significant number of patients with major depressive disorder. Current pharmacological approaches often do not provide sufficient therapeutic results, prompting the need for innovative treatments. This review summarizes recent advances in TRD management, including non-pharmacological therapies such as transcranial magnetic stimulation, deep brain stimulation, electroconvulsive therapy, and vagus nerve stimulation, and describes their mechanisms of action. Novel pharmacotherapies, particularly glutamatergic modulators like ketamine and esketamine, have shown promising results with esketamine being available to eligible patients in Poland since 2023 within a drug program. Electroconvulsive therapy remains an effective treatment for TRD, usually with small side effects mainly including transient memory impairment, headache, or cardiovascular changes. Transcranial magnetic stimulation is a non-invasive procedure with proven efficacy; therefore several psychiatric organizations recommend it as a treatment option for major depressive disorder in their clinical guidelines. Deep brain stimulation is a relatively new treatment modality for TRD, with its primary risk being associated with the required neurosurgical procedure. Vagus nerve stimulation seems to be a promising adjunctive treatment for TRD, showing significant improvements in depressive symptoms, especially at higher electrical doses but with no side effects. While these treatments appear to have potential, personalized approaches are crucial for optimizing outcomes. Future research should focus on refining the techniques, improving safety profiles, and validating the long-term efficacy.

Psychedelic iatrogenic structural dissociation: an exploratory hypothesis on dissociative risks in psychedelic use

This paper introduces the hypothesis of Psychedelic Iatrogenic Structural Dissociation (PISD), proposing that psychedelics may reactivate dissociated traumatic material, increasing the risk of psychological destabilization in trauma-exposed individuals. Grounded in structural dissociation theory, this framework suggests that psychedelics can disrupt the balance between daily functioning (the Apparently Normal Personality, ANP) and trauma-related responses (the Emotional Personality, EP), leading to the resurfacing of unintegrated memories. A review of recent studies highlights persistent adverse effects associated with psychedelic use, including emotional dysregulation, identity fragmentation, derealization, and perceptual disturbances, particularly among individuals with early trauma histories. To mitigate these risks and facilitate trauma processing, integration practices, body-focused therapies, and structured social support systems are proposed as key interventions. Additionally, emerging neurophysiological models suggest that psychedelics may reconfigure dissociative processes through the modulation of entrenched patterns, potentially facilitating trauma integration or increasing vulnerability to destabilization, depending on individual and contextual factors. These findings underscore the necessity of trauma-informed screening, preparation, and integration protocols to enhance the safety and efficacy of psychedelic therapies, particularly for vulnerable populations.

The diverse effects of ketamine, jack-of-all-trades: a narrative review

Ketamine, an N-methyl-D-aspartic acid receptor antagonist that was first discovered in 1962, has become established in anaesthesia providing dose-dependent anaesthetic, sedative, and analgesic effects. Ketamine, however, also acts on a wide range of other cellular targets, resulting in interesting and diverse effects on both physiological and pathological processes. Potential beneficial properties of ketamine include cardiovascular stability for patients undergoing sedation or anaesthesia, analgesia in both acute and chronic pain, bronchodilation in severe refractory asthma, anti-inflammatory properties particularly in sepsis, tumour inhibition, and antidepressant properties with marked ability to reverse suicidal ideation. The reluctance to adopt ketamine into routine practice is likely attributable in part to the stigma and negative reputation associated with its perceived side-effects and potential for abuse. This review explores the diverse properties and therapeutic potentials of ketamine being investigated across different fields whilst also identifying areas for ongoing and future research. Given the diverse range of potential benefits and promising early work, ketamine should be the focus of ongoing research in multiple different specialty areas. This includes areas relevant to anaesthesia and perioperative medicine, such as acute and chronic pain management, ICU sedation, and even tumour suppression in those undergoing surgical resection of malignancies.

Activation of SIRT1 by Hydroxysafflor Yellow A Attenuates Chronic Unpredictable Mild Stress-Induced Microglia Activation and Iron Death in Depressed Rats

BACKGROUND

Hydroxysafflor yellow A (HSYA), the main active ingredient in safflower, possesses antioxidant and anti-inflammatory activities. We confirmed in our previous study that HSYA exerts antidepressant effects, but further investigation is needed to uncover the exact mechanism. Herein, we aimed to explore the antidepressant effects of HSYA based on microglial activation and ferroptosis studies.

METHODS

The chronic unpredictable mild stress (CUMS) procedure was used to establish a depression model in rats. Behavioral tests were conducted on rats after HSYA administration. Iba-1 immunostaining was used to determine the activation of microglia in the hippocampus. We examined the iron ion level using a colorimetric method. Assayed by western blot for protein expression.

RESULTS

Rats receiving HSYA showed enhanced spatial learning and memory abilities, as well as improvements in depression-like behaviors. HSYA administration reduced Iba-1 expression in CUMS rats' hippocampus, indicating that HSYA suppressed microglial activation. HSYA inhibited CUMS-induced Fe2+ concentration and promoted ferroptosis-related protein GPX4 and SLC7A11 expression. HSYA treatment also elevated SIRT1 and Nrf2 protein levels, while p-p65 protein levels decreased in the hippocampus of CUMS rats.

CONCLUSION

HSYA exerts an antidepressant-like effect by inhibiting microglia activation in the hippocampus and inducing SIRT1/Nrf2/NF-kB signaling.

Investigating novel pharmacological strategies for treatment-resistant depression: focus on new mechanisms and approaches

INTRODUCTION

A substantial number of patients exhibit treatment-resistant depression (TRD), posing significant challenges to clinicians. The discovery of novel molecules or mechanisms that may underlie TRD pathogenesis and antidepressant actions is highly needed.

AREAS COVERED

Using the PubMed database, the authors searched for emerging evidence of novel approaches for TRD based on experimental and human studies. Herein, the authors discuss the mechanisms underlying glutamatergic antagonists, modulators of the opioid system, and tryptamine-derivate psychedelics as well as the emerging platforms to investigate novel pharmacological targets for TRD. A search for clinical trials investigating novel agents and interventions for TRD was also conducted.

EXPERT OPINION

The understanding of the multiple pathophysiological mechanisms involved in TRD may add further value to the effective treatment, contributing to a more personalized approach. Esketamine was approved for the treatment of TRD and novel drugs with rapid antidepressant actions such as psilocybin and buprenorphine have also been investigated as potential therapeutic strategies. Over the past decades, technological advances such as omics approaches have broadened our knowledge regarding molecular and genetic underpinnings of complex conditions like TRD. Omics approaches could open new avenues for investigating glial-mediated mechanisms, including their crosstalk with neurons, as therapeutic targets in TRD.

Examining the impact of comorbid posttraumatic stress disorder on ketamine's real-world effectiveness in treatment-resistant depression

Depression with comorbid posttraumatic stress disorder (PTSD) is associated with more severe symptoms and a reduced response to traditional treatments. Although ketamine shows promise as a rapid-acting antidepressant for treatment-resistant depression (TRD), its effectiveness in patients with comorbid PTSD remains underexplored. Therefore, we conducted a retrospective analysis of 134 patients from the Canadian Rapid Treatment Center of Excellence to compare the effectiveness of four ketamine infusions (0.5-0.75 mg/kg) in reducing symptoms of depression and PTSD in TRD patients with and without comorbid PTSD. A repeated-measures linear mixed model was used to evaluate the impact of comorbid PTSD on ketamine's antidepressant effectiveness, measured by the Quick Inventory of Depressive Symptomatology Self-Report (QIDS-SR16). Paired samples t-tests were used to assess changes in PTSD symptoms, measured by the PTSD Checklist for DSM-5 (PCL-5). We found a significant main effect of time on QIDS-SR16 scores, F(4, 209.32) = 36.67, p < 0.001, but no significant group-by-time interaction (p = 0.895), suggesting that comorbid PTSD did not impact the antidepressant effectiveness of ketamine. Significant improvements in PTSD symptoms were observed in overall PCL-5 scores, t(66) = 6.66, p < 0.001, and across all PCL-5 symptom clusters with moderate to large effect sizes. In a real-world sample of TRD patients, ketamine was effective in reducing symptoms of depression and PTSD, regardless of PTSD comorbidity. These findings highlight ketamine's potential as a novel intervention for a patient population that is frequently non-responders to conventional treatments. Future randomized controlled trials should explore mediating factors of improvement and long-term effects.

How Do People Who Undergo Ketamine Treatment for a Psychiatric Problem Subjectively Experience This Intervention? A Meta-Synthesis of Qualitative Studies

Ketamine treatment has shown promising effects for different mental disorders. Yet, little is known on how people who receive ketamine for a psychiatric problem subjectively experience undergoing this intervention. We conducted a systematic literature search to identify relevant qualitative research on the first-person experience of undergoing ketamine treatment in a psychiatric context. 24 eligible studies were identified and analysed using a thematic meta-synthesis approach. Three main themes were identified. First, 'The Ketamine treatment experience can be understood as a three-stage journey with unique clinical features at each stage'. Second, 'The subjective experience of acute ketamine treatment is multifaceted and complex'. Third, 'Ketamine treatment can have different positive effects-but what happens if it does not work?'. In summary, the subjective experience of receiving ketamine treatment for a psychiatric problem can be understood as a journey whereby patients move towards, then undergo, and eventually depart from ketamine. Before treatment, the experiential focus lies on expectations, hopes, and feelings towards the drug. During treatment, the drug's multifaceted psychotropic effects and how they are emotionally appraised become central to experience. Once treatment is finished, the focus is on the presence or absence of clinically relevant effects. The conceptual framework we propose can guide further qualitative research on this topic and aid mental health professionals to better understand the experience of patients who undergo ketamine treatment for a psychiatric problem.

Repeated subcutaneous esketamine on treatment-resistant depression: An open-label dose titration study

BACKGROUND

Ketamine has gained prominence as one of the most effective therapeutic options in unipolar treatment-resistant depression (TRD). However, most studies related to the antidepressant action of ketamine used intravenous (IV) or intranasal (IN) administration. The subcutaneous (SC) route of administration is a promising alternative, as it results in plasma levels comparable to IV, causes fewer side effects, and is easier and cheaper to administer than both IV and/or IN routes.

METHODS

In this context, we conducted an open-label clinical trial for investigating the efficacy and safety of 8 weekly sessions of SC esketamine in TRD patients (n = 30).

RESULTS

At the end of the treatment, a partial response rate of 26.09 %, a response rate of 52.17 % and remission rate of 34.78 % were observed, assessed by Montgomery-Åsberg Depression Rating Scale. Moreover, the self-reported depressive symptoms, as measured by the Beck Depression Inventory II (BDI-II), significantly decreased from the baseline to the final session, and the improvements were sustained throughout the week. Follow-up evaluations (BDI-II) up to the sixth month consistently showed scores lower than the baseline.

LIMITATIONS

The small sample size and the drop-out during the follow-up phase may limit the generalizability of the findings. Additionally, the absence of a control group necessitates cautious interpretation of causality.

CONCLUSIONS

This groundbreaking study, which addresses SC esketamine treatment for TRD, reported promising response and remission rates, as well as sustained antidepressant effects. It highlights the need for further research to improve and expand our knowledge of this innovative, more accessible, and cost-effective therapeutic approach.

Ketamine-Assisted Psychotherapy for Antisocial Personality Disorder: A Case Report

There are currently no evidence-based treatment guidelines for antisocial personality disorder (ASPD). Instead, treatment typically focuses on comorbid conditions. There is currently no literature documenting cases or research, theoretical or otherwise of using ketamine-assisted therapy or any other psychedelic therapy in cases of ASPD. In this case report, a 43-year-old man seeking ketamine-assisted psychotherapy (KAP) for alcoholism and depression was diagnosed with comorbid antisocial personality disorder. A series of psycholytic (low dose) ketamine therapy sessions and other integrative approaches over the course of 3 years results in resolution of severe alcoholism, reduction in violent thoughts about people and the world, and a reduction in depression symptoms. With additional precautions, utilizing a ketamine-assisted psychotherapy approach led to clinical improvements in depression, alcohol abuse, and ASPD traits.

Association of intravenous ketamine with change in depressive symptoms in a large integrated health care system

OBJECTIVE

Racemic ketamine intravenous treatments (KIT) are widely used in community clinics for treatment resistant depression (TRD), but we lack studies on symptom improvement during standardized delivery to clinically complex patients with TRD. We aimed to assess depression symptom change for patients receiving standardized KIT for TRD in a large integrated health care delivery system relative to similar patients receiving standard medication management.

METHODS

In this retrospective cohort study (n = 570), depression symptom change measured by the 9-item Patient Health Questionnaire (PHQ-9) was examined in 143 adults with TRD receiving 0.5mg/kg 40-minute KIT infusion twice weekly for 3 weeks from 01/01/2018 to 12/31/2022 and 427 contemporaneous patients with medication management (MM) matched on variables including sex, race, age, and baseline depression symptom score. We excluded patients with major neurocognitive disorder, schizophrenia, or pregnancy.

RESULTS

The KIT group was more likely to achieve depression response (PHQ-9 reduction >50 %) compared to MM (adjusted risk ratio [aRR]= 1.72, 95 % CI = 1.17 - 2.53; P = 0.006). The KIT group (8 % vs 5 %) was more likely to achieve depression remission (i.e. PHQ-9 < 5); however, the adjusted risk with KIT vs MM was not statistically significant. Baseline depression symptoms were associated with higher depression symptoms at follow up, as were co-occurring anxiety and personality disorders.

CONCLUSIONS

KIT was significantly associated with depression response and symptom improvement compared to MM. Clinicians should consider comorbid personality disorder, anxiety disorders, and baseline depression severity as potential predictors of KIT and other treatment response in TRD.

Rapid and sustained reduction of treatment-resistant PTSD symptoms after intravenous ketamine in a real-world, psychedelic paradigm

BACKGROUND

Traditional treatments for post-traumatic stress disorder (PTSD) often show limited success with high dropout. Ketamine, an N-methyl-D-aspartate antagonist known for rapid antidepressant effects, has decreased PTSD symptoms in some studies but not in others. Administering ketamine in ways that parallel psychedelic-assisted treatments-including preparatory, integration, sensory immersion, and psychotherapy sessions-could decrease PTSD symptoms meaningfully.

METHODS

A retrospective sample of 117 screened outpatients with elevated PTSD Checklist for DSM-5 (PCL-5) scores received intravenous ketamine in supportive environments. The protocol included preparation, intention-setting, and integration sessions accompanying at least six administrations. Administration sessions included eye shades and evocative music paralleling typical psychedelic therapy trials.

RESULTS

Mean PCL scores decreased from 52.54 (SD = 12.01) to 28.78 (SD = 16.61), d = 1.64. Patients tolerated treatment well, with no serious adverse events. Covariates, including age, gender, days between PCL assessments, number of psychiatric medications, and suicidal ideation were not significant moderators; concomitant psychotherapy did reach significance, d = 0.51. Of the 117 patients' final PCL scores, 88 (75.21%) measures suggested clinically meaningful improvement and 72 (61.54%) suggested remission of PTSD symptoms.

CONCLUSION

Intravenous ketamine in supportive environments, with hallmarks of psychedelic therapy, preceded large reductions in PTSD symptoms. These results highlight ketamine's potential when delivered in this manner, suggesting environmental factors might account for some variation seen in previous work. Given the molecule's cost, minimal interaction with other psychiatric medications, and legal status, intravenous ketamine in a psychedelic paradigm may be a promising option for PTSD unresponsive to other treatments.

Ketamine use in a large global sample: Characteristics, patterns of use and emergency medical treatment

BACKGROUND

Ketamine's popularity has surged globally in the past decade, especially among young men. Emergency department visits due to its toxicity remain relatively rare, often linked to co-occurring use of other substances.

AIMS

Using data from the Global Drug Survey (GDS) 2018, this study explored the correlates associated with lifetime and past-year ketamine use, and estimated the socio-demographic characteristics, usage patterns and experiences of respondents seeking emergency medical treatment (EMT) after ketamine use.

METHODS

Secondary analysis of GDS 2018, an online cross-sectional survey on drug use patterns conducted between November 2017 and January 2018.

RESULTS

The survey received 130,761 valid responses, with 5.93% reporting lifetime ketamine use, of which 57.70% used ketamine within the past year. Predominantly, respondents were from Germany, England and Denmark. Within the past year, 8.55% met the criteria for ketamine dependence. Respondents who used ketamine in their lifetime tended to be young (mean (x̄) = 27.37 years), men, heterosexual and of white ethnicity. Younger age (x̄ = 24.84 years), gay sexual orientation, student status, past-year use of other drugs and no lifetime mental health diagnosis were associated with past-year ketamine use. Among 4477 respondents reporting past-year ketamine use, 120 adverse events were reported, with less than 0.10% prompting EMT seeking.

CONCLUSION

The study reveals frequent ketamine use but low harm occurrence, underscoring the complex interplay between ketamine use, substance use and dependence, and related factors. This underscores the need to reassess EMT priorities, implement tailored harm reduction strategies and incorporate comprehensive screening for addressing ketamine and substance dependence challenges.

Modulation of the endocannabinoid system by (S)-ketamine in an animal model of depression

Ketamine (KET) is recognized as rapid-acting antidepressant, but its mechanisms of action remain elusive. Considering the role of endocannabinoids (eCB) in stress and depression, we investigated if S-KET antidepressant effects involve the regulation of the eCB system using an established rat model of depression based on selective breeding: the Flinders Sensitive Line (FSL) and their controls, the Flinders Resistant Line (FRL). S-KET (15 mg/kg) effects were assessed in rats exposed to the open field and forced swimming test (FST), followed by analysis of the eCB signaling in the rat prefrontal cortex (PFC), a brain region involved in depression neurobiology. Changes in eCB receptors and enzymes were assessed at mRNA and protein levels (qPCR and western blot), CB1 binding ([3H]SR141716A autoradiography) and endocannabinoid content (lipidomics). The results demonstrated that the depressive behavior in FSL was negatively correlated with 2-AG levels, which were restored upon acute S-KET treatment. Although S-KET decreased CB1 and FAAH gene expression in FSL, there were no significant changes at protein levels. [3H]SR141716A binding to CB1 receptors was increased by S-KET and in silico analysis suggested that it binds to CB1, CB2, GPR55 and FAAH. Overall, S-KET effects correlated with an increased endocannabinoid signaling in the PFC, but systemic treatment with rimonabant failed to block its behavioral effects. Altogether, our results indicate that S-KET facilitates eCB signaling in the PFC of FSL. The inability of rimonabant to block the antidepressant effect of S-KET highlights the complexity of its interaction with the ECS, warranting further investigation into the molecular pathways.

The quest for optimal ketamine dosing formula in treatment-resistant major depressive disorder

BACKGROUND

Emerging evidence indicates that intravenous ketamine is effective in managing treatment-resistant unipolar and bipolar depression. Clinical studies highlight its favorable efficacy, safety, and tolerability profile within a dosage range of 0.5-1.0 mg/kg based on actual body weight. However, data on alternative dosage calculation methods, particularly in relation to body mass index (BMI) and therapeutic outcomes, remain limited.

METHODS

This retrospective analysis of an open-label study aims to evaluate dose calculation strategies and their impact on treatment response among inpatients with treatment-resistant major depressive disorder (MDD) (n = 28). The study employed the Boer and Devine formulas to determine lean body mass (LBM) and ideal body weight (IBW), and the Mosteller formula to estimate body surface area (BSA). The calculated doses were then compared with the actual doses administered or converted to a dosage per square meter for both responders and non-responders.

RESULTS

Regardless of treatment response, defined as a reduction of 50% in the Montgomery-Åsberg Depression Rating Scale, the use of alternative ketamine dosing formulas resulted in underdosing compared to the standardized dose of 0.5 mg/kg. Only two participants received higher doses (102.7% and 113.0%) when the Devine formula was applied.

CONCLUSIONS

This study suggests that ketamine dosing formulas, alternative to the standardized 0.5 mg/kg based on body weight, may lead to underdosing and potentially impact outcome interpretation. To enhance dosing accuracy, future studies should consider incorporating body impedance analysis and waist-to-hip ratio measurements, as this study did not account for body composition.

Genetic ablation of the isoform γ of PI3K decreases antidepressant efficacy of ketamine in male mice

About one-third of major depressive disorder (MDD) patients demonstrate unresponsiveness to classic antidepressants, and even the clinical efficacy of fast-acting drugs such as ketamine varies significantly among patients with treatment-resistant depression. Nevertheless, the lack of suitable animal models that mimic a possible ketamine-resistant phenotype challenges the understanding of resistance to drug treatment. In this study, we showed that PI3Kγ knock-out (KO) mice do not respond to classical doses of ketamine and classical antidepressants. PI3Kγ KO mice were unresponsive to both the rapid and sustained antidepressant-like effects of a single dose of ketamine in the forced swimming test. Additionally, they were unresponsive to the antidepressant-like effects induced by the tricyclic antidepressant imipramine and the selective serotonin reuptake inhibitor fluoxetine. However, acute pharmacological inhibition of PI3Kγ did not block the antidepressant-like effect of ketamine, showing that a chronic deficiency of the PI3Kγ-mediated pathway is necessary for the effects of classic doses of ketamine and antidepressants. Therefore, we propose that PI3Kγ participates in the antidepressant activity and is likely implicated in the neurobiology and phenotype observed in patients with MDD who demonstrate treatment resistance.

Residual Depressive Symptoms in Treatment-Resistant Bipolar Depression Following Short-Term Ketamine Administration

BACKGROUND

Residual symptoms are frequently observed in a significant number of patients with depression, indicating an unmet need for effective management strategies to achieve functional recovery.

OBJECTIVE

This observational study aimed to evaluate the impact of ketamine infusions on depressive symptoms in patients with bipolar disorder who continued their baseline psychotropic and chronic somatic treatments.

METHODS

Datasets of the two consecutive real-world registries (NCT04226963 for 2019-2022; NCT05565352 from 2023 onward) for the tertiary reference center for psychiatry at the Medical University of Gdańsk (Poland) for the safety and tolerability of ketamine use in mood and anxiety disorders were retrospectively analyzed. Depressive symptoms were assessed using the Inventory of Depressive Symptomatology Self-Report 30 (IDS-SR30). Residual symptoms were identified in patients who achieved a treatment response, defined as a 50% or greater reduction in Montgomery-Åsberg Depression Rating Scale (MADRS) scores from baseline to the seventh infusion.

RESULTS

Overall, 14 out of 22 patients met the criteria for response. The most commonly persistent depressive symptoms included sad mood (85.7%), view of my future (78.6%), difficulty falling asleep, and leaden paralysis/physical energy (both 71.4%), with the most severe being difficulty falling asleep (64.3%) and sad mood (42.9%).

CONCLUSIONS

This observational post hoc analysis indicates that the most frequently observed residual depressive symptoms were low mood, altered view of future, sleep disturbances, and low energy levels. This study should be treated with caution as causality does not apply, however, it reports on a real-world population of subjects with treatment-resistant bipolar depression. Establishing standardized definitions for residual symptoms could enhance the quality and comparability of future research in this area.

Perioperative administration of sub-anesthetic ketamine/esketamine for preventing postpartum depression symptoms: A trial sequential meta-analysis

OBJECTIVE

Postpartum depression (PPD) is a major mental health issue affecting 10%-15% of women globally. This meta-analysis synthesized updated evidence on sub-anesthetic ketamine/esketamine's efficacy in preventing PPD.

METHODS

Randomized controlled trials (RCTs) comparing ketamine/esketamine to a placebo for PPD prevention were searched without language restriction. Primary outcomes were PPD risk at 1- and 4-6-week postpartum. Secondary outcomes included the difference in depression scores and risk of adverse events. Trial sequential analysis (TSA) was conducted to validate the reliability.

RESULTS

A meta-analysis of 22 RCTs (n = 3,463) showed that ketamine/esketamine significantly decreased PPD risk at 1- (risk ratio [RR], 0.41; 95% confidence interval [CI], 0.3-0.57) and 4-6-week (RR, 0.47; 95%CI, 0.35-0.63) follow-ups. Consistently, participants receiving ketamine/esketamine had lower depression-related scores at 1- (standardized mean difference [SMD], -0.94; 95%CI, -1.26 to -0.62) and 4-6-week (SMD, -0.89; 95%CI, -1.25 to -0.53) follow-ups. Despite potential publication bias, TSA confirmed the evidence's reliability. Subgroup analysis showed that ketamine/esketamine's preventive effect on 1-week PPD was consistent, regardless of administration timing, type of agents, or total dosage (<0.5 vs. ≥0.5 mg/kg). For the 4-6-week period, PPD risk was favorably reduced only with postoperative administration or the use of esketamine, with the total dosage having no observed influence. Participants on ketamine/esketamine experienced more frequency of hallucinations (RR, 4.77; 95%CI, 1.39-16.44) and dizziness (RR, 1.36; 95%CI, 1.02-1.81).

CONCLUSION

Our findings advocate for the postoperative administration of low-dose ketamine/esketamine to avert PPD, which needed additional research for confirmation.

Glutamatergic Modulators for Major Depression from Theory to Clinical Use

Major depressive disorder (MDD) is a chronic, burdensome, highly prevalent disease that is characterized by depressed mood and anhedonia. MDD is especially burdensome as approved monoamine antidepressant treatments have weeks-long delays before clinical benefit and low remission rates. In the past 2 decades, a promising target emerged to improve patient outcomes in depression treatment: glutamatergic signaling. This narrative review provides a high-level overview of glutamate signaling in synaptogenesis and neural plasticity and the implications of glutamate dysregulation in depression. Based on this preclinical evidence implicating glutamate in depression and the rapid improvement of depression with ketamine treatment in a proof-of-concept trial, a range of N-methyl-D-aspartate (NMDA)-targeted therapies have been investigated. While an array of treatments has been investigated in registered phase 2 or 3 clinical trials, the development of most of these agents has been discontinued. Multiple glutamate-targeted antidepressants are actively in development, and two are approved. Nasal administration of esketamine (Spravato®) was approved by the US Food and Drug Administration (FDA) in 2019 to treat adults with treatment-resistant depression and in 2020 for adults with MDD with acute suicidal ideation or behavior. Oral combination dextromethorphan-bupropion (AXS-05, Auvelity® extended-release tablet) was FDA approved in 2022 for the treatment of MDD in adults. These approvals bolster the importance of glutamate in depression and represent an exciting breakthrough in contemporary psychiatry, providing new avenues of treatment for patients as first-line therapy or with either poor response or unacceptable side effects to monoaminergic antidepressants.

Treatment-resistant depression: molecular mechanisms and management

Due to the heterogeneous nature of depression, the underlying etiological mechanisms greatly differ among individuals, and there are no known subtype-specific biomarkers to serve as precise targets for therapeutic efficacy. The extensive research efforts over the past decades have not yielded much success, and the currently used first-line conventional antidepressants are still ineffective for close to 66% of patients. Most clinicians use trial-and-error treatment approaches, which seem beneficial to only a fraction of patients, with some eventually developing treatment resistance. Here, we review evidence from both preclinical and clinical studies on the pathogenesis of depression and antidepressant treatment response. We also discuss the efficacy of the currently used pharmacological and non-pharmacological approaches, as well as the novel emerging therapies. The review reveals that the underlying mechanisms in the pathogenesis of depression and antidepressant response, are not specific, but rather involve an interplay between various neurotransmitter systems, inflammatory mediators, stress, HPA axis dysregulation, genetics, and other psycho-neurophysiological factors. None of the current depression hypotheses sufficiently accounts for the interactional mechanisms involved in both its etiology and treatment response, which could partly explain the limited success in discovering efficacious antidepressant treatment. Effective management of treatment-resistant depression (TRD) requires targeting several interactional mechanisms, using subtype-specific and/or personalized therapeutic modalities, which could, for example, include multi-target pharmacotherapies in augmentation with psychotherapy and/or other non-pharmacological approaches. Future research guided by interaction mechanisms hypotheses could provide more insights into potential etiologies of TRD, precision biomarker targets, and efficacious therapeutic modalities.

IN Esketamine and IV Ketamine: Results of a multi-site observational study assessing the effectiveness and tolerability of two novel therapies for treatment-resistant depression

Intravenous (IV) ketamine and intranasal (IN) esketamine are novel therapies to manage treatment resistant depression within major depressive disorder (MDD-TRD). This is a multi-site observational study aiming to assess the real-world effectiveness and tolerability of these novel therapies in the management of MDD-TRD. 53 patients were referred to receive IV ketamine (n = 26, 69.23 % female, 52.81 ± 14.33 years old) or IN esketamine (n = 27, 51.85 % female, 43.93 ± 13.57 years old). Treatment effectiveness was assessed using the Montgomery and Åsberg Depression Rating Scale (MADRS) for depression severity and item 10 of the MADRS for suicidal ideation (SI). Tolerability was assessed by systematically tracking side effects and depersonalization using the 6-item Clinician administered dissociative symptom scale (CADSS-6). The data was analyzed using descriptive statistics, risk ratio and effect size. Both IV ketamine and IN esketamine significantly reduced depressive symptoms and suicidal ideation by treatment endpoint. Patients receiving IN esketamine, and patients receiving IV ketamine had a similar risk of developing side effects. All side effects reported were mild and transient. These results suggested that both IV ketamine and IN esketamine are effective in the management of depressive symptoms and were well tolerated. Therefore, the results of this study could serve to inform clinical practice.

At-home, telehealth-supported ketamine treatment for depression: Findings from longitudinal, machine learning and symptom network analysis of real-world data

BACKGROUND

Improving safe and effective access to ketamine therapy is of high priority given the growing burden of mental illness. Telehealth-supported administration of sublingual ketamine is being explored toward this goal.

METHODS

In this longitudinal study, moderately-to-severely depressed patients received four doses of ketamine at home over four weeks within a supportive digital health context. Treatment was structured to resemble methods of therapeutic psychedelic trials. Patients receiving a second course of treatment were also examined. Symptoms were assessed using the Patient Health Questionnaire (PHQ-9) for depression. We conducted preregistered machine learning and symptom network analyses to investigate outcomes (osf.io/v2rpx).

RESULTS

A sample of 11,441 patients was analyzed, demonstrating a modal antidepressant response from both non-severe (n = 6384, 55.8 %) and severe (n = 2070, 18.1 %) baseline depression levels. Adverse events were detected in 3.0-4.8 % of participants and predominantly neurologic or psychiatric in nature. A second course of treatment helped extend improvements in patients who responded favorably to initial treatment. Improvement was most strongly predicted by lower depression scores and age at baseline. Symptoms of Depressed mood and Anhedonia sustained depression despite ongoing treatment.

LIMITATIONS

This study was limited by the absence of comparison or control groups and lack of a fixed-dose procedure for ketamine administration.

CONCLUSIONS

At-home, telehealth-supported ketamine administration was largely safe, well-tolerated, and associated with improvement in patients with depression. Strategies for combining psychedelic-oriented therapies with rigorous telehealth models, as explored here, may uniquely address barriers to mental health treatment.

[Psychedelic and dissociative agents in psychiatry: challenges in the treatment]

With the discovery of the antidepressive effects of ketamine and the increasing withdrawal of the pharmaceutical industry from the development of new psychotropic drugs, the psychiatric research into the clinical application of hallucinogens in psychiatry has literally blossomed in the last two decades. Promising results for various treatment approaches with psychedelic agents, such lysergic acid diethylamide (LSD) and psilocybin, and dissociative agents, such as ketamine and esketamine, have raised great hopes among researchers, clinicians and patients in recent years, so that there was already talk of a new era in psychiatry. As one of the first of these substances, in December 2019 intranasal esketamine was approved in the USA and the EU for the treatment of treatment-resistant depression and Switzerland followed in 2020. Recently, psilocybin was approved in Australia, Canada and Switzerland for compassionate use in exceptional cases for the treatment of depression, while large approval studies with various psychedelic agents are currently ongoing worldwide. The medical application of psychedelic agents and ketamine/esketamine is considered to be safe; however, as with all new forms of treatment it is of crucial importance that, in addition to the hopes, the specific challenges of these new treatment approaches must also be carefully considered and assessed. Excessive expectations and an insufficient risk-benefit estimation are detrimental to the patients and the reputation of the treating physician. Although a possible paradigm shift in the care of mental health is already being discussed, this review article consciously concentrates on the possible risks of treatment and the methodological weaknesses of the studies carried out so far.

The Pharmacological Management of Ketamine Use Disorder: A Systematic Review

OBJECTIVES

There has been limited evidence synthesis examining treatment of ketamine use disorder. We aimed to conduct a systematic review to assess the efficacy and tolerability of pharmacological interventions in the management of ketamine use disorder.

METHODS

We searched MEDLINE, EMBASE, PsychINFO, and CENTRAL (Cochrane Central Register of Controlled Trials) from database inception to November 14, 2023, for studies of any design that reported on any pharmacological intervention in the management of ketamine use disorder. We extracted any reported measure of efficacy or tolerability and assessed outcome quality using the GRADE (Grading of Recommendations Assessment, Development, and Evaluation) framework. We planned to combine outcomes using random-effects meta-analysis, where this was not possible results were reported narratively.

RESULTS

Twelve studies met the inclusion criteria reporting on 368 participants. These comprised 1 controlled trial, 2 retrospective case series, and 9 case reports. Two studies reported on ketamine intoxication, 6 on withdrawal, and 4 on craving/relapse prevention. All studies reported only descriptive outcomes, and all evidence was of very low quality. Benzodiazepine regimens and haloperidol were reported to have potential utility in intoxication and withdrawal, whereas naltrexone, lamotrigine, and a combination of paliperidone palmitate and bupropion were reported to have potential utility in craving/relapse prevention.

CONCLUSIONS

There is a paucity of research into pharmacological management of ketamine use disorder. The limited very low-quality evidence suggests benzodiazepine regimens may be most salient for future exploration in management of ketamine intoxication and withdrawal, whereas case reports suggest naltrexone, lamotrigine, and paliperidone palmitate plus bupropion may potentially merit further investigation with regard to craving/relapse prevention.

Treatment-emergent symptoms during short-term ketamine administration in treatment-resistant bipolar depression: A retrospective cross-sectional descriptive study

Symptoms that emerge during pharmacological treatment of bipolar depression are frequently observed, underscoring the necessity for comprehensive treatment monitoring. This observational study sought to observe the correlation of eight intravenous ketamine infusions with treatment-emergent depressive symptoms in treatment-resistant bipolar depression patients who maintained their baseline psychotropic and chronic somatic treatments. Depressive symptoms were evaluated using the Inventory of Depressive Symptomatology Self-Report 30 (IDS-SR30). Treatment-emergent symptoms TES were defined as symptoms absent at baseline but present at the conclusion of the study. The most common TES included decreased appetite, increased weight, hypersomnia, and diurnal mood variation. Conversely, feelings of sadness, altered perceptions of the future, decreased interest in sex, and physical discomfort were absent in all patients. Notably, 13.6 % of patients reported thoughts of death or suicide. Larger-scale studies, integrating clinician-rated and patient-reported outcome measures, are essential to deepen our understanding of treatment-emergent symptoms. Establishing regulatory or professional definitions for treatment-emergent symptoms is warranted to improve the robustness of future research endeavors.

Comparison between Single-Dose and Two-Dose Psilocybin Administration in the Treatment of Major Depression: A Systematic Review and Meta-Analysis of Current Clinical Trials

Current pharmacological treatments for major depressive disorder (MDD) are often only partially effective, with many patients experiencing no significant benefit, leading to treatment-resistant depression (TRD). Psilocybin, a classical serotonergic psychedelic, has emerged as a notable emerging treatment for such disorders. The aim of this systematic review and meta-analysis is to summarize and discuss the most recent evidence about the therapeutic effects of single-dose and two-dose psilocybin administration on the severity of depressive symptoms, as well as compare the efficacy of these interventions among patients with a primary diagnosis of MDD or TRD. Articles were collected from EBSCOhost and PubMed following the PRISMA guidelines, yielding 425 articles with 138 duplicates. After screening 287 records, 12 studies met the eligibility criteria and were included in the review. A quantitative analysis of the studies indicates that psilocybin is highly effective in reducing depressive symptoms severity among patients with primary MDD or TRD. Both single-dose and two-dose psilocybin treatments significantly reduced depressive symptoms severity, with two-dose administration sometimes yielding more pronounced and lasting effects. However, it is unclear if this was solely due to dosage or other factors. Future research should include standardized trials comparing these dosing strategies to better inform clinical practice.

The role of KCNQ channel activators in management of major depressive disorder

Depression, a complex disorder with significant treatment challenges, necessitates innovative therapeutic approaches to address its multifaceted nature and enhance treatment outcomes. The modulation of KCNQ potassium (K+) channels, pivotal regulators of neuronal excitability and neurotransmitter release, is a promising innovative therapeutic target in psychiatry. Widely expressed across various tissues, including the nervous and cardiovascular systems, KCNQ channels play a crucial role in modulating membrane potential and regulating neuronal activity. Recent preclinical evidence suggests that KCNQ channels, particularly KCNQ3, contribute to the regulation of neuronal excitability within the reward circuitry, offering a potential target for alleviating depressive symptoms, notably anhedonia. Studies using animal models demonstrate that interventions targeting KCNQ channels can restore dopaminergic firing balance and mitigate depressive symptoms. Human studies investigating the effects of KCNQ channel activators, such as ezogabine, have shown promising results in alleviating depressive symptoms and anhedonia. The aforementioned observations underscore the therapeutic potential of KCNQ channel modulation in depression management and highlight the need and justification for phase 2 and phase 3 dose-finding studies as well as studies prespecifying symptomatic targets in depression including anhedonia.

The Search for Consistency in Residual Symptoms in Major Depressive Disorder: A Narrative Review

Residual symptoms are prevalent in major depressive disorder (MDD), encompassing a wide spectrum of symptoms such as sleep disturbances, changes in weight and appetite, cognitive impairment, and anxiety. These symptoms consistently impair daily functioning, diminish quality of life, and forecast disease relapse. Despite their clinical significance, residual symptoms lack a unified definition, potentially leading to confusion with treatment-emergent symptoms and ambiguity across studies, thereby hindering the generalizability of research findings. While some research identifies insomnia and mood disturbances as critical indicators, other studies emphasize different symptoms or find no significant correlation. Inconsistencies in defining residual symptoms, as well as methodological differences across studies, contribute to these conflicting results. While clinicians focus on alleviating negative symptoms to improve functional status, patients often prioritize achieving positive affect and overall well-being as essential components of successful treatment. It necessitates a comprehensive approach to patient care in depression. This review explores the phenomenon of residual symptoms in MDD, focusing on the ambiguity in definitions, clinical characteristics, and their impact on long-term outcomes. The lack of a standardized regulatory or academic definition for residual symptoms leads to varied interpretations among clinicians, underscoring the need for standardized terminology to guide effective treatment strategies and future research.

Repurposing General Anesthetic Drugs to Treat Depression: A New Frontier for Anesthesiologists in Neuropsychiatric Care

During the last 100 years, the role of anesthesiologists in psychiatry has focused primarily on facilitating electroconvulsive therapy and mitigating postoperative delirium and other perioperative neurocognitive disorders. The discovery of the rapid and sustained antidepressant properties of ketamine, and early results suggesting that other general anesthetic drugs (including nitrous oxide, propofol, and isoflurane) have antidepressant properties, has positioned anesthesiologists at a new frontier in the treatment of neuropsychiatric disorders. Moreover, shared interest in understanding the biologic underpinnings of anesthetic drugs as psychotropic agents is eroding traditional academic boundaries between anesthesiology and psychiatry. This article presents a brief overview of anesthetic drugs as novel antidepressants and identifies promising future candidates for the treatment of depression. The authors issue a call to action and outline strategies to foster collaborations between anesthesiologists and psychiatrists as they work toward the common goals of repurposing anesthetic drugs as antidepressants and addressing mood disorders in surgical patients.

A randomized controlled pilot study of daily intravenous ketamine over three days for treatment-resistant depression

BACKGROUND

Studies have confirmed the rapid antidepressant action of ketamine in depressive episodes. Nevertheless, a standardized procedure for the delivery of ketamine infusion in individuals suffering from treatment-resistant depression, particularly in terms of infusion frequency and total dosage, remains undetermined. In addition, an efficacious ketamine regimen for persistent pain management involved a continuous 10-day infusion period with no notable adverse effects. Consequently, the primary objective of this study was to evaluate the antidepressant capacity of consecutive ketamine infusions spanning over three successive days, the duration of therapeutic response, and the overall safety profile of the treatment.

METHODS

In this randomized controlled trial, participants aged 18-64 with treatment-resistant depression were randomized to receive either intravenous ketamine or midazolam (used as an active placebo) for 40 min daily over three consecutive days. Statistical analysis using repeated measures ANOVA was employed to assess the changes in the total score of the Montgomery-Åsberg Depression Rating Scale (MADRS) and the clinical global impression-Severity from the initial assessment to 10 and 31 days post-infusion. Additionally, the duration of response and remission was evaluated using Kaplan-Meier survival analysis.

RESULTS

Out of 33 randomized participants, 20 underwent the treatment as planned. By day 10th, the ketamine group had a mean reduction in MADRS score of 12.55 (95% CI = 6.70-18.09), whereas the midazolam group had a decrease of 17.22 (95% CI = 11.09-23.36). This pattern continued to day 31, with ketamine showing a mean score decrease of 13.73 (95% CI = 7.54-19.91) and midazolam a fall of 12.44 (95% CI = 5.61-19.28). Both treatments were well tolerated, with dissociative symptoms in the ketamine group being temporary and ceasing by the end of each infusion.

CONCLUSION

Intravenous ketamine given for three consecutive days did not show a notable antidepressant advantage when compared to the active placebo midazolam, highlighting the need for further research into effective treatments schedules for treatment-resistant depression.

TRIAL REGISTRATION

NCT05026203, ClinicalTrials.gov, registered on 24/08/2021.

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.

Baseline monocyte count predicts symptom improvement during intravenous ketamine therapy in treatment-resistant depression: a single-arm open-label observational study

Background

Neuroinflammatory processes in depression are associated with treatment resistance to conventional antidepressants. Ketamine is an effective new therapeutic option for treatment-resistant depression (TRD). Its well-established immunomodulatory properties are hypothesized to mediate its antidepressant effect. In this context, higher levels of inflammation may predict a better treatment response. However, conclusive evidence for this hypothesis is lacking. We thus investigated whether standard peripheral inflammatory cell markers and C-reactive protein (CRP) levels could predict symptom improvement during intravenous ketamine therapy in TRD patients.

Methods

27 participants with TRD were treated with six weight-adjusted intravenous ketamine infusions (0.5 mg/kg bodyweight) over three weeks. Baseline assessments included CRP, absolute monocyte count (AMC), and absolute neutrophil count (ANC). Depression severity was measured using the Montgomery-Åsberg Depression Rating Scale (MADRS) at baseline (D1), after the first (D3) and before the last ketamine infusion (D18). Raters were blinded for the baseline laboratory assessments.

Results

13 participants responded to ketamine treatment, and 8 participants partially responded. Baseline AMC showed a strong negative correlation with MADRS change at D3 (r=-0.57, p=0.002) and at D18 (r =-0.48, p=0.010), indicating that a high baseline AMC was associated with greater symptom improvement. A generalized linear model confirmed the association of baseline AMC with symptom improvement during ketamine treatment when additionally accounting for age, sex, and body mass index. Specifically, baseline AMC demonstrated predictive value to discriminate responders and partial responders from non-responders, but lacked discriminative ability between partial responders and responders. Baseline ANC correlated with the MADRS changes at D3 (r=-0.39, p=0.046), while CRP values did not correlate at all.

Conclusions

Our prospective single-arm open-label observational study demonstrated that baseline AMC reliably predicted symptom improvement during intravenous ketamine treatment in TRD patients. AMC could therefore serve as a simple and easily accessible marker for symptom improvement during ketamine therapy in daily clinical practice. Future studies with larger sample sizes and a more detailed longitudinal assessment of AMC subtypes are needed to better understand the specific relationship between monocytes and the neuromodulatory effects of ketamine.

Licit use of illicit drugs for treating depression: the pill and the process

Psilocybin, MDMA, and ketamine have emerged as potentially effective treatments for rapid amelioration of the symptoms of mood and related psychiatric disorders. All clinical data collected so far with regard to psilocybin or MDMA, which have reported positive outcomes for treating depression, anxiety, posttraumatic stress disorder, and drug or alcohol use disorders, have involved clinician-assisted intervention. While the case for ketamine is assumed to be different, the first report of the successful use of ketamine in psychiatry for treating depression was in combination with psychotherapy, and an emerging literature suggests that the subjective state of individual experiences with ketamine predicts clinical outcome. This Review will focus on (a) a brief review of the literature, showing that the context or the process of drug administration has been an integrative component of published work; (b) the importance of clinical trials to compare the efficacy of the drug ("pill") as a stand-alone treatment versus drug in combination with clinician-assisted psychological support ("process"); and (c) suggestions for future approaches in animal models that take into account the role of systems and behavioral neuroscience in explaining a potential role for context, experience, and expectancy in drug effect.

Ketamine Therapy in Complex Cases: A Cautionary Tale of Exacerbated Personality Traits and the Crucial Role of Comprehensive Follow-Up and Psychosocial Interventions

This case report examines the unexpected increase in suicidal ideation following ketamine infusion therapy in a 75-year-old female with a history of treatment-resistant depression. Despite ketamine's established efficacy in treating depression and acute suicidality, this patient's condition deteriorated posttreatment. The report delves into the patient's complex background, including psychosocial stressors, genetic predisposition to depression, and a history of personality traits that may have influenced her response to ketamine. This case underscores the importance of cautious administration of ketamine, especially in patients with personality disorders, and calls for deeper understanding and individualized treatment plans in mental health care. It is a reminder of the complexities involved in treating mental health conditions and the varying effects of treatments like ketamine on different individuals.

A meta-analysis of the effects of ketamine on suicidal ideation in depression patients

The treatment of suicidal ideation in patients with depression has been a major problem faced by psychiatric and emergency departments, and reasonable drug selection is particularly important. Ketamine has been shown to reduce suicidal ideation rapidly, but the strength of the effect is unclear and there is little evidence-based medical evidence to support this. We systematically searched all articles published on PubMed, Cochrane Library, Web of Science, CNKI and EMBASE. Stata 15 and R 4.1.3 were used for meta-analysis, and odds ratios were calculated in fixed effects or random effects models based on the heterogeneity test results. Our search resulted in 505 articles; we analyzed 14 studies, which included 1,380 participants. The 14 studies included 10 randomized controlled trial (RCT) studies and 4 single-arm studies. Our study suggests that, ketamine has a significant therapeutic effect on suicidal ideation throughout the treatment cycle. We performed network meta-analyses(NMA) and pairwise meta-analyses to compare the efficacy of ketamine in the reduction of suicidal ideation. There was a significant reduction in suicidal ideation within the first day after treatment (NMA ketamine day1 RR = 10.02, 95%CI = 4.24 to 23.68). In repeated treatment, the degree of recovery of suicidal ideation after the last dose was significantly greater than that after the first dose (RR = 0.56, 95%CI = 0.51 to 0.62). Recovery of suicidal ideation was also significantly better in the treatment end point than in the placebo group at the same time point (NMA ketamine day26 RR = 4.29, 95%CI = 1.41 to 13.08). This is the first network meta-analysis to demonstrate the role of ketamine in the alleviation of suicidal ideation. Our network meta-analysis also compared the effects of different drugs at different time points, which was not done in previous studies. This is of great reference significance for future drug research andrational drug use.

Facts and myths about use of esketamine for treatment-resistant depression: a narrative clinical review

Introduction and aims

Treatment-resistant depression (TRD) occurs when at least two different antidepressants, taken at the right dosage, for adequate period of time and with continuity, fail to give positive clinical effects. Esketamine, the S-enantiomer of ketamine, was recently approved for TRD treatment from U.S. Food and Drug Administration and European Medicine Agency. Despite proved clinical efficacy, many misconceptions by clinicians and patients accompany this medication. We aimed to review the most common "false myths" regarding TRD and esketemine, counterarguing with evidence-based facts.

Methods

The keywords "esketamine", "treatment resistance depression", "depression", "myth", "mythology", "pharmacological treatment", and "misunderstanding" were entered in the main databases and combined through Boolean operators.

Results

Misconceptions regarding the TRD prevalence, clinical features and predictors have been found. With respect of esketamine, criteria to start treatment, dissociative symptoms, potential addiction and aspects of administration and monitoring, were found to be affected by false beliefs by clinicians and patients.

Discussion and conclusion

TRD represents a challenging condition, requiring precise diagnosis in order to achieve patient's full recovery. Esketamine has been proved as an effective medication to treat TRD, although it requires precautions. Evidence can inform clinical practice, in order to offer this innovative treatment to all patients with TRD.

Hype or hope? Ketamine for the treatment of depression: results from the application of deep learning to Twitter posts from 2010 to 2023

OBJECTIVE

To investigate societal perceptions of ketamine's use in depression therapy by analysing Twitter posts from January 1, 2010 to April 1, 2023.

METHODS

Using Twitter as the social media platform of choice, and employing search terms based on (depression OR depressed OR depressive) AND (ketamine OR esketamine OR Spravato), we collected English-language tweets from January 1, 2010, to April 1, 2023. Using unsupervised machine learning and natural language processing (NLP) techniques, including Bidirectional Encoder Representations from Transformers (BERT) and BERTopic, the study identified prevalent topics surrounding public chatter around the use of ketamine in depression treatment. Manual thematic analyses further refined these topics into themes.

RESULTS

Out of an initial dataset of 99,405 tweets, after removing duplicate tweets, re-tweets and tweets posted by organizations over Twitter, 18,899 unique tweets from presumably individual users were analysed. Analysis of temporal trends revealed a shift in public attitudes, particularly after the United States Food and Drug Administration (FDA)'s 2019 approval of ketamine for depression. Three major themes emerged: a changing regulatory landscape, cautious optimism, and personal experiences with the drug. There was an initial spike in discussions post-FDA approval in 2019. Thereafter, cautious optimism (Theme 2) decreased among the general public, with more personal accounts (Theme 3) highlighting the potential benefits for some treatment-resistant patients. Limitations of the study include Twitter's inherent biases towards younger, English-speaking demographics.

CONCLUSION

In summary, the public's multifaceted perception leans towards a hopeful stance on ketamine's therapeutic potential for depression.

Recurrent Serotonin Syndrome After Ketamine-assisted Electroconvulsive Therapy: A Case Report and Review of the Literature

Serotonin (5-HT) syndrome (SS) consists of changes in mental status as well as autonomic and neuromuscular changes. Though not well understood, serotonergic pathways have been implicated in the mechanism of action of electroconvulsive therapy (ECT). Ketamine has been used as an induction agent in ECT and as therapy for treatment-resistant depression. Utilizing a case report and literature review, we explored the underlying serotonergic mechanisms of ECT and ketamine by which a syndrome of serotonin toxicity may be precipitated. We describe the case of a 72-year-old woman who developed recurrent SS on 2 occasions in similar circumstances involving the administration of ketamine for ECT. In our literature review, we found 5 cases in which SS was associated with ECT and 1 case linking ketamine to SS. There is emerging evidence that the mechanism of ECT involves 5-HT1A and 5-HT2A receptors, the same receptors that are involved in SS. ECT can transiently increase the permeability of the blood-brain barrier, leading to increased levels of antidepressants in the brain. ECT can, therefore, enhance 5-HT transmission and the likelihood of SS in the presence of serotonergic agents. The effect of ketamine on 5-HT transmission is mediated by the glutamate α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor. Ketamine increases α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid activity in the medial prefrontal cortex, which leads to downstream 5-HT release through glutamate. Through this mechanism, ketamine can increase 5-HT transmission, leading to SS. To our knowledge, this is the only case report of recurrent SS with concurrent use of ECT and ketamine. As ketamine is frequently used in ECT and many patients undergoing ECT are on serotonergic medications, it is important to recognize ketamine as a potential risk factor for SS. There is no evidence for added efficacy when combining ECT and ketamine. Thus, one should proceed with caution when combining these treatments. The burgeoning use of ketamine in ambulatory settings makes it necessary to elucidate the risks, which we discuss further. More research is needed into the mechanisms of ketamine and ECT, specifically how the combination of these treatments influence 5-HT levels.

IV low dose ketamine infusions for treatment resistant depression: Results from a five-year study at a free public clinic in an academic hospital

Individuals with major depressive disorder and treatment resistant depression (MDD-TRD) have limited and sometimes poorly tolerated therapeutic options. Low dose ketamine has presented promising and potent antidepressant effects in this population. To support the existent literature, we conducted a longitudinal study examining five years of real-world clinical data on the use of IV low-dose ketamine alongside standard care for MDD-TRD outpatients. For this study we collected demographic information, clinical scale scores, side effects and dropout data. The data was analyzed using descriptive statistics, effect size using Cohen's D analysis, and multivariate ANOVA (MANOVA) to determine the impact of sociodemographic variables. 71 outpatients (50.28 years old, SD: 14.26; female 74.65%) were included in the analysis. The results showed a significant reduction in depressive symptoms and suicide ideation (SI) by treatment endpoint. 54.93% of patients responded to the treatment, 78.26% experienced transient and mild side effects, and 11.27% of dropped out of the treatment. Multivariate analysis showed that the demographic variables did not impact treatment effect or tolerability. The results of this study suggest that IV low dose ketamine treatment is effective, fast-acting, and well tolerated for the management of depressive symptoms and SI in patients with MDD-TRD in naturalistic clinical practice.

Psychiatric and legal considerations for ketamine treatment within prison settings

The fundamental right to equivalence of health care in prison settings encompasses the provision of medication to address mental health conditions. Considering the increased risk for self-harm among individuals dealing with depression, the limited effectiveness of conservative antidepressants is a major challenge in psychiatry. The high prevalence of suicidal tendencies within prison populations underscores the imperative for state-of-the-art pharmacological treatment to uphold adequate health care standards. Notably, the denial of access to effective medication could be deemed a violation of human rights of people living in prison according to international treaties, domestic law, and United Nations normative standards of detention. This article presents the authors' perspective on the accessibility of ketamine treatment in prison settings, discussing psychiatric and legal considerations as well as current challenges in this context. Implementing novel psychopharmacological interventions may alleviate the distress experienced by individuals struggling with depressive symptoms and suicidality. At the same time, unprecedented treatment alternatives bring along potential issues, including limited understanding of long-term effects and the risk of abuse. Given the scarce data-availability, a pressing need exists for further research on the benefits and risks of ketamine treatment within prison populations.

Ketamine in multiple treatment-resistant depressed inpatients: A naturalistic cohort study

BACKGROUND

Ketamine has emerged as an effective treatment option for patients with treatment-resistant depression. However, there is limited evidence of the benefits of ketamine in inpatients with multiple treatment resistance (MTR), who far exceed the formal criteria for treatment resistance and suffer from extensive psychiatric comorbidities.

OBJECTIVE

The aim of this naturalistic study was to provide preliminary evidence for the use of ketamine in the treatment of MTR depression in a naturalistic inpatient setting.

METHODS

Seventy-seven patients (mean age 45.1 ± 13.8 years) were treated with intravenous or intranasal ketamine (1068 administrations) twice weekly for five weeks, followed by maintenance therapy if clinically indicated. Treatment effects were assessed with the BDI, and side effects were assessed by clinicians. We analyzed dose- and route of application-related changes in depression severity, response and remission rates as well as effects on suicidality and frequency of adverse events.

RESULTS

Depression severity and suicidality decreased in the acute treatment phase and these changes persisted during the maintenance therapy phase. A total of 28.9 % of the patients met the criteria for response, and 15 % met the criteria for remission. The initial treatment response was highly predictive of the outcome at the end of the acute treatment phase. None of the reported side effects required medical intervention. High-dose intravenous ketamine (0.75-1 mg/kg) resulted in the most pronounced clinical effects.

LIMITATIONS

This observational, retrospective, and naturalistic study may be subject to bias and did not allow control of external variables.

CONCLUSIONS

We outlined a clinically feasible, high-dose ketamine treatment regimen for hospitalized patients with MTR depression.

How different definition criteria may predict clinical outcome in treatment resistant depression: Results from a prospective real-world study

Management of treatment-resistant depression (TRD) remains a major public health challenge, also due to the lack of a consensus around TRD definition. We investigated the impact of different definitions of TRD on identifying patients with distinct features in terms of baseline characteristics, treatment strategies, and clinical outcome. We conducted a prospective naturalistic study on 538 depressed inpatients. Patients were screened for treatment resistance by two TRD definitions: looser criteria (lTRD) and stricter criteria (sTRD). We compared baseline characteristics, treatment and clinical outcome between the TRD groups and their non-TRD counterparts. 52.97 % of patients were identified as lTRD, only 28.81 % met the criteria for sTRD. sTRD patients showed lower rates of remission and slower symptom reduction compared to non-TRD patients and received more challenging treatments. Surprisingly, patients identified as sTRD also exhibited lower rates of psychiatric comorbidities, including personality disorders, substance abuse, or alcohol misuse. Stricter TRD criteria identify patients with worse clinical outcomes. Looser criteria may lead to overdiagnosis and over treatment. Clinical features known to be possible risk factors for TRD, as psychiatric comorbidities, showed to be more suggestive of a "difficult to manage" depression rather than a proper TRD.

Hype or hope? High placebo response in major depression treatment with ketamine and esketamine: a systematic review and meta-analysis

Background

Ketamine and esketamine offer a novel approach in the pharmacological treatment of major depressive disorder (MDD). This meta-analysis aimed to investigate the placebo response in double-blind, randomized controlled studies (RCTs) on patients with MDD receiving ketamine or esketamine.

Methods

For this systematic review and meta-analysis Medline (PubMed), Cochrane Central Register of Controlled Trials (CENTRAL), PsycInfo and Embase databases were systematically searched for citations published up to March 17, 2023. A total number of 5017 abstracts was identified. Quality of the included trials was assessed with the Cochrane risk-of-bias tool. The meta-analysis was performed using a restricted maximum likelihood model. This study is registered with PROSPERO, number CRD42022377591.

Results

A total number of 14 studies and 1100 participants (593 in the medication group and 507 in the placebo group) meeting the inclusion criteria were selected. We estimated the pooled effect sizes of the overall placebo (d pl = -1.85 [CI 95%: -2.9 to -0.79] and overall treatment (dtr = -2.57; [CI 95% -3.36 to -1.78]) response. The overall placebo response accounts for up to 72% of the overall treatment response. Furthermore, we performed subgroup analysis of 8 studies for the for the 7 days post-intervention timepoint. Seven days post-intervention the placebo response (d pl 7d = -1.98 [CI 95%: -3.26 to -0.69]) accounts for 66% of the treatment response (d tr 7d = - 3.01 [CI 95%, -4.28 to -1.74]).

Conclusion

Ketamine and esketamine show large antidepressant effects. However, our findings suggest that the placebo response plays a significant role in the antidepressant response and should be used for the benefit of the patients in clinical practice.

Systematic review registration

https://www.crd.york.ac.uk/prospero/, identifier CRD42022377591.

Patient-reported outcomes on sleep quality and circadian rhythm during treatment with intravenous ketamine for treatment-resistant depression

Background

Intravenous (IV) ketamine is a rapid acting antidepressant used primarily for treatment-resistant depression (TRD). It has been suggested that IV ketamine's rapid antidepressant effects may be partially mediated via improved sleep and changes to the circadian rhythm.

Objectives

This study explores IV ketamine's association with changes in patient-reported sleep quality and circadian rhythm in an adult population with TRD.

Methods

Adult patients (18-64 years) with TRD scheduled for IV ketamine treatment were recruited to complete patient rated outcomes measures on sleep quality using the Pittsburgh Sleep Quality Index (PSQI) and circadian rhythm using the Morningness-Eveningness Questionnaire (MEQ). Over a 4-week course of eight ketamine infusions, reports were obtained at baseline (T0), prior to second treatment (T1), prior to fifth treatment (T2), and 1 week after eighth treatment (T3).

Results

Forty participants with TRD (mean age = 42.8, 45% male) were enrolled. Twenty-nine (72.5%) had complete follow-up data. Paired t tests revealed statistically significant improvements at the end of treatment in sleep quality (PSQI) (p = 0.003) and depressive symptoms (Clinically Useful Depression Outcome Scale-Depression, p < 0.001) while circadian rhythm (MEQ) shifted earlier (p = 0.007). The PSQI subscale components of sleep duration (p = 0.008) and daytime dysfunction (p = 0.001) also improved. In an exploratory post hoc analysis, ketamine's impact on sleep quality was more prominent in patients with mixed features, while its chronobiotic effect was prominent in those without mixed features.

Conclusion

IV ketamine may improve sleep quality and advance circadian rhythm in individuals with TRD. Effects may differ in individuals with mixed features of depression as compared to those without. Since this was a small uncontrolled study, future research is warranted.