Anhedonia and substance dependence: clinical correlates and treatment options

Anhedonia as a Transdiagnostic Symptom Across Psychological Disorders: A Network Approach

Background

Anhedonia is apparent in different mental disorders and is suggested to be related to dysfunctions in the reward system and/or affect regulation. It may hence be a common underlying feature associated with symptom severity of mental disorders.

Methods

We constructed a cross-sectional graphical Least Absolute Shrinkage and Selection Operator (LASSO) network and a relative importance network to estimate the relationships between anhedonia severity and the severity of symptom clusters of major depressive disorder (MDD), anxiety sensitivity (AS), attention-deficit hyperactivity disorder (ADHD), and autism spectrum disorder (ASD) in a sample of Dutch adult psychiatric patients (N = 557).

Results

Both these networks revealed anhedonia severity and depression symptom severity as central to the network. Results suggest that anhedonia severity may be predictive of the severity of symptom clusters of MDD, AS, ADHD, and ASD. MDD symptom severity may be predictive of AS and ADHD symptom severity.

Conclusions

The results suggest that anhedonia may serve as a common underlying transdiagnostic psychopathology feature, predictive of the severity of symptom clusters of depression, AS, ADHD, and ASD. Thus, anhedonia may be associated with the high comorbidity between these symptom clusters and disorders. If our results will be replicated in future studies, it is recommended for clinicians to be more vigilant about screening for anhedonia and/or depression severity in individuals diagnosed with an anxiety disorder, ADHD and/or ASD.Appeared originally in Psychol Med 2023; 53:3908-3919.

Noradrenergic Mechanisms and Circuitry of Hyperkatifeia in Alcohol Use Disorder

Hyperkatifeia, the manifestation of emotional distress or pain, is a conceptual framework gaining traction throughout the alcohol and other substance use fields as an important driver of addiction. It is well known that previous or current negative life experiences can serve as powerful motivators for excessive alcohol consumption and precipitate the development of an alcohol use disorder (AUD). A major hallmark of later stages of AUD is the emergence of hyperkatifeia during withdrawal, which can persist well into protracted abstinence to drive relapse. Given these complex interactions, understanding the specific neuroadaptations that lie at the intersection of hyperkatifeia and AUD can inform ongoing therapeutic development. The monoamine norepinephrine is of particular interest. Noradrenergic dysfunction is implicated in AUD, anxiety, chronic stress, depression, and emotional and physical pain. Importantly, there are key sexual dimorphisms within the noradrenergic system that are thought to differentially impact the development and trajectory of AUD in women and men. In the current review, we discuss past and recent work on noradrenergic influences at each stage of the AUD cycle (binge/intoxication, withdrawal/negative affect, and preoccupation/anticipation) through the lens of hyperkatifeia. Evidence from these studies support the prioritization of norepinephrine-specific drug development to treat AUD and the identification of AUD subpopulations that may benefit the most from these therapies (e.g., women or people with comorbid chronic pain or anxiety/stress disorders).

Anhedonia and impulsivity in college alcohol use: A path analysis

OBJECTIVE

Alcohol use is a substantial problem among college students and has several negative consequences. The current study examined the associations between anhedonia and alcohol use and related problems via impulsive behavior (e.g., negative urgency, sensation seeking). We parsed anhedonia into four specific facets: consummatory, anticipatory, recreational, and social anhedonia.

PARTICIPANTS

Six hundred and forty college students aged 18-25 were included in the final analysis.

METHOD

Data were collected via Amazon Mechanical Turk. Self-report inventories assessing for anhedonia, alcohol use, impulsive behavior, and depressed mood were utilized.

RESULTS

Recreational consummatory anhedonia was negatively associated with alcohol use and alcohol-related problems through negative urgency. Recreational consummatory anhedonia also had significant negative associations with alcohol consumption via sensation seeking. Further, social anticipatory anhedonia was positively associated with alcohol use and related problems via negative urgency.

CONCLUSIONS

This study highlights important associations between anhedonia, impulsivity, and alcohol use and related problems.

Effect of DLPFC rTMS on anhedonia and alpha asymmetry in depressed patients

Anhedonia, a core symptom of depression, has been defined as the loss of pleasure or lack of reactivity to pleasurable stimuli. Considering the relevance of alpha asymmetry to MDD and anhedonia, we explored the effect of dorsolateral prefrontal cortex (DLPFC) stimulation on frontal and posterior EEG alpha asymmetry (FAA and PAA, respectively), in this exploratory investigation. 61 participants randomly received sham (n = 11), bilateral (BS; n = 25), or unilateral stimulation (US; n = 25) of the DLPFC. The Snaith-Hamilton Pleasure Scale (SHAPS) was administered. FAA and PAA were calculated by subtracting the natural log-transformed alpha power of the right (F8 or T6) from that of the left (F7 or T5) EEG channel. Furthermore, alpha peak was defined as the frequency where alpha power was at its maximum. BS and US both reduced anhedonia symptoms in the active compared to the sham group. Even non-responders in the BS group showed a decreased anhedonia. Interestingly in the BS group, only the patients who showed a right-lateralized FAA or PAA at baseline showed a reduction in anhedonia. However, in the US group, only patients with left-lateralized FAA or right-lateralized PAA showed a decrease in anhedonia. PAA at baseline predicted symptoms post treatment. Furthermore, a significant positive correlation between baseline alpha peak values and SHAPS scores post treatment were found in the BS group. PAA was a better predictor of anhedonia and reduction of depressive symptoms in both groups. BS may produce larger effects with regard to anhedonia.

Greater neural delay discounting on reward evaluation in anhedonia

Background/objective

Recent years have witnessed a surge of interest in dissecting the anticipatory and the consummatory aspects of anhedonia in terms of temporal dynamics. However, few research has directly examined reward valuation as a function of time in anhedonia.

Method

Using a delay discounting task, this event-related potential study examined the neural representation of rewards available immediately or in six months in a high-anhedonia group (N = 40) and a low-anhedonia group (N = 40) recruited from a nonclinical sample.

Results

We found that anhedonia was associated with greater neural delay discounting during reward evaluation. This was evidenced by a blunted effect of reward magnitude on the reward positivity (RewP) in the high-anhedonia compared to the low-anhedonia group when the rewards would be delivered six months later. Representation similarity analysis revealed that the aberration in processing delayed rewards is further corroborated by enhanced neural coding of reward time during the RewP period in the high-anhedonia versus low-anhedonia group.

Conclusions

These findings provide empirical evidence to show that anhedonia is driven by a blunted neural representation of future rewards instead of immediate rewards, suggesting an inability to form mental representations of future positive experiences in anhedonia.

Subjective time dilation in abstinent patients with alcohol use disorder

INTRODUCTION

Patients with alcohol use disorder (AUD) may have distortions in time perception. This study investigated subjective time dilation (the tendency to perceive a time interval longer than it is) and its association with craving and impulsivity in AUD.

METHOD

Thirty abstinent male inpatients with AUD (age 29-60 years) and thirty sex-, age-, and education-matched healthy controls completed a temporal generalization task, which assessed the preference (point of subjective equality, PSE) and sensitivity of time perception in the second range. Craving for alcohol was assessed using the Alcohol Urge Questionnaire. Impulsivity was assessed using a delay discounting task and the Barratt Impulsiveness Scale-11. A comprehensive battery of neuropsychological tests was used to measure executive function (flanker task, symbol digit modalities test, trail-making test-A/B), negative emotionality (Beck Depression Inventory-II, Self-rating Anxiety Scale), and incentive salience (monetary incentive delay task) following the Addictions Neuroclinical Assessment (ANA) framework.

RESULTS

AUD patients exhibited a smaller PSE than healthy controls, perceiving a time interval 8% longer than it was. AUD patients with a smaller PSE showed a greater craving for alcohol but not greater impulsivity. Exploratory factor analysis incorporating the PSE and ANA measures revealed four latent factors. The PSE loaded highly onto a factor reflecting time perception but not three other factors reflecting executive function, negative emotionality, and incentive salience.

CONCLUSIONS

AUD patients exhibit a pathological form of subjective time dilation, which is associated with a greater craving for alcohol. Time perception may be an independent functional dimension for understanding addictive behaviors in AUD.

Inclusion of Individuals With Lived Experiences in the Development of a Digital Intervention for Co-Occurring Depression and Cannabis Use: Mixed Methods Investigation

BACKGROUND

Existing interventions for co-occurring depression and cannabis use often do not treat both disorders simultaneously and can result in higher rates of symptom relapse. Traditional in-person interventions are often difficult to obtain due to financial and time limitations, which may further prevent individuals with co-occurring depression and cannabis use from receiving adequate treatment. Digital interventions can increase the scalability and accessibility for these individuals, but few digital interventions exist to treat both disorders simultaneously. Targeting transdiagnostic processes of these disorders with a digital intervention-specifically positive valence system dysfunction-may yield improved access and outcomes.

OBJECTIVE

Recent research has highlighted a need for the inclusion of individuals with lived experiences to assist in the co-design of interventions to enhance scalability and relevance of an intervention. Thus, the purpose of this study is to describe the process of eliciting feedback from individuals with elevated depressed symptoms and cannabis use and co-designing a digital intervention, Amplification of Positivity-Cannabis Use Disorder (AMP-C), focused on improving positive valence system dysfunction in these disorders.

METHODS

Ten individuals who endorsed moderate to severe depressive symptoms and regular cannabis use (2-3×/week) were recruited online via Meta ads. Using a mixed methods approach, participants completed a 1-hour mixed methods interview over Zoom (Zoom Technologies Inc) where they gave their feedback and suggestions for the development of a mental health app, based on an existing treatment targeting positive valence system dysfunction, for depressive symptoms and cannabis use. The qualitative approach allowed for a broader investigation of participants' wants and needs regarding the engagement and scalability of AMP-C, and the quantitative approach allowed for specific ratings of intervention components to be potentially included.

RESULTS

Participants perceived the 13 different components of AMP-C as overall helpful (mean 3.9-4.4, SD 0.5-1.1) and interesting (mean 4.0-4.9, SD 0.3-1.1) on a scale from 1 (not at all) to 5 (extremely). They gave qualitative feedback for increasing engagement in the app, including adding a social component, using notifications, and being able to track their symptoms and progress over time.

CONCLUSIONS

This study highlights the importance of including individuals with lived experiences in the development of interventions, including digital interventions. This inclusion resulted in valuable feedback and suggestions for improving the proposed digital intervention targeting the positive valence system, AMP-C, to better match the wants and needs of individuals with depressive symptoms and cannabis use.

From mood to use: Using ecological momentary assessments to examine how anhedonia and depressed mood impact cannabis use in a depressed sample

Anhedonia and depressed mood are two cardinal symptoms of major depressive disorder (MDD). Prior work has demonstrated that cannabis consumers often endorse anhedonia and depressed mood, which may contribute to greater cannabis use (CU) over time. However, it is unclear (1) how the unique influence of anhedonia and depressed mood affect CU and (2) how these symptoms predict CU over more proximal periods of time, including the next day or week (rather than proceeding weeks or months). The current study used data collected from ecological momentary assessment (EMA) in a sample with MDD (N = 55) and employed mixed effects models to detect and predict weekly and daily CU from anhedonia and depressed mood over 90 days. Results indicated that anhedonia and depressed mood were significantly associated with CU, yet varied at daily and weekly scales. Moreover, these associations varied in both strength and directionality. In weekly models, less anhedonia and greater depressed mood were associated with greater CU, and directionality of associations were reversed in the models looking at any CU (compared to none). Findings provide evidence that anhedonia and depressed mood demonstrate complex associations with CU and emphasize leveraging EMA-based studies to understand these associations with more fine-grained detail.

The role of anhedonia in the relationship between adverse childhood experiences (ACEs), alcohol use disorder symptoms, and food addiction symptoms in a sample of emerging adults with histories of heavy drinking

Previous research has shown that (ACEs) are associated with negative health outcomes, including depression, problematic alcohol use, and disordered patterns of overeating, including food addiction (FA). Moreover, anhedonia, or an inability to feel pleasure, has been also shown to increase risk for problematic alcohol use, as well as FA. It is possible that anhedonia may be implicated in health risk behaviors as individuals with anhedonia may seek out highly hedonic activities. The purpose of the present study was to explore the direct and indirect relationship between ACEs and alcohol use disorder (AUD) and FA symptoms via anhedonia in a diverse sample of emerging adults with histories of heavy drinking. A cross-sectional, quantitative design was used. The sample was 42.6% male, 45.5% White, and 39.9% Black, and the average age of participants was 22.64 (SD = 1.01). A confirmatory factor analysis was used to specify the model, and structural equation modeling was used to test the hypotheses. The initial measurement model was overidentified and demonstrated acceptable to favorable fit. Standardized results from a bootstrap analysis of the structural regression model showed significant direct effects of ACEs on FA and AUD symptoms. Results also found a significant indirect effect of ACEs on AUD symptoms through anhedonia, though this indirect effect was not significant for FA. Anhedonia could be a key target for the prevention and treatment of problematic alcohol use. Future research should examine the role of anhedonia in the maintenance of FA in nonheavy drinking samples. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Genetic Associations of Anhedonia: Insights into Overlap of Mental and Somatic Disorders

BACKGROUND

Anhedonia is characterized by a reduced ability to anticipate, experience, and/or learn about pleasure. This phenomenon has a transdiagnostic nature and is one of the key symptoms of mood disorders, schizophrenia, addictions, and somatic conditions.

AIM

To evaluate the genetic architecture of anhedonia and its overlap with other mental disorders and somatic conditions.

METHODS

We performed a genome-wide association study of anhedonia on a sample of 4,520 individuals from a Russian non-clinical population. Using the available summary statistics, we calculated polygenic risk scores (PRS) to investigate the genetic relationship between anhedonia and other psychiatric or somatic phenotypes.

RESULTS

No variants with a genome-wide significant association were identified. PRS for major depression, bipolar disorder, and schizophrenia were significantly associated with anhedonia. Conversely, no significant associations were found between PRS for anxiety and anhedonia, which aligns well with existing clinical evidence. None of the PRS for somatic phenotypes attained a significance level after correction for multiple comparisons. A nominal significance for the anhedonia association was determined for omega-3 fatty acids, type 2 diabetes mellitus, and Crohn's disease.

CONCLUSION

Anhedonia has a complex polygenic architecture, and its presence in somatic diseases or normal conditions may be due to a genetic predisposition to mood disorders or schizophrenia.

Effect of venlafaxine on anhedonia and amotivation in patients with major depressive disorder

OBJECTIVE

Serotonin norepinephrine reuptake inhibitors (SNRIs) have been postulated to afford benefits in alleviating anhedonia and amotivation. This post hoc pooled analysis evaluated the effect of venlafaxine XR, an SNRI, on these symptoms in patients with major depressive disorder (MDD).

METHODS

Data was pooled from five short-term randomized, placebo-controlled studies of venlafaxine XR for the treatment of MDD, comprising 1087 (venlafaxine XR, n = 585; placebo, n = 502) adult subjects. The change from baseline score in the MADRS anhedonia factor (based on items 1 [apparent sadness], 2 [reported sadness], 6 [concentration difficulties], 7 [lassitude], and 8 [inability to feel]) for anhedonia, and in motivational deficits (based on 3 items of HAM-D17: involvement in work and activities, psychomotor retardation, and energy level [ie, general somatic symptoms]) for amotivation, were measured through 8 weeks. Mixed model repeated measures (MMRMs) were used to analyze changes over time and ANCOVA to analyze the change from baseline at week 8 with LOCF employed to handle missing data.

RESULTS

At the end of 8 weeks, the change from baseline was significantly greater in patients on venlafaxine XR in both anhedonia (mean, 95% CI: -2.73 [-3.63, -1.82], p < 0.0001) and amotivation scores (mean, 95% CI: -0.78 [-1.04, -0.52], p < 0.0001) than those on placebo. For both measures, the between-group separation from baseline was statistically significant starting from week 2 onwards, and it increased over time.

CONCLUSION

This analysis demonstrates that venlafaxine XR is effective in improving symptoms of anhedonia and motivational deficits in patients with MDD.

Evaluating the effectiveness of a mobile app-based self-guided psychological interventions to reduce relapse in substance use disorder: protocol for a randomized controlled trial

Background

Substance Use Disorder (SUD) persists as a significant public health challenge worldwide, with an estimated prevalence of approximately 10-15% across the global populace. This condition is characterized by a notably high risk of lapses and relapses, even subsequent to treatment interventions. Mobile health interventions, owing to their widespread accessibility, emerge as a promising approach to diminish the risk of relapse post-treatment and to broaden the scope of care, especially in regions with a scarcity of trained medical professionals.

Method

This study is designed to assess the effectiveness of mobile interventions in mitigating cravings and preventing lapses among individuals diagnosed with SUD. Employing a two-armed, randomized controlled trial framework, the study will evaluate a self-administered psychological intervention delivered through a mobile application, Nałogometr 2.0. Over a period of three months, participants will engage with intervention modules that primarily incorporate mindfulness techniques and Cognitive Behavioral Therapy (CBT) principles. Ecological Momentary Assessment (EMA) will be utilized to gather longitudinal data on a range of variables that are indicative of craving intensity and the risk of lapse. In addition to this, a monthly-administered battery of questionnaires will be employed to gauge the severity of substance dependence, as well as to measure levels of anxiety, depression, and overall life satisfaction.

Results

Results will be submitted for publication in peer-reviewed journals.

Clinical trial registration

https://clinicaltrials.gov/, identifier [NCT05730504].

Personality characteristics, not clinical symptoms, are associated with anhedonia in a community sample: A preliminary investigation

Anhedonia is a salient transdiagnostic psychiatric symptom associated with increased illness severity and chronicity. Anhedonia is also present to varying degrees in non-clinical cohorts. Here, we sought to examine factors influencing expression of anhedonia. Participants (N = 335) were recruited through the Nathan Kline Institute-Rockland Sample, an initiative to deeply phenotype a large community sample across the lifespan. Utilizing a data-driven approach, we evaluated associations between anhedonia severity, indexed by Snaith-Hamilton Pleasure Scale (SHAPS), and 20 physical, developmental, and clinical measures, including Structured Clinical Interview for DSM-IV, Beck Depression Inventory, State-Trait Anxiety Inventory, NEO Five-Factor Inventory-3 (NEO-FFI-3), BMI, Hemoglobin A1C, and demography. Using a bootstrapped AIC-based backward selection algorithm, seven variables were retained in the final model: NEO-FFI-3 agreeableness, extraversion, and openness to experience; BMI; sex; ethnicity; and race. Though median SHAPS scores were greater in participants with psychiatric diagnoses (18.5) than those without (17.0) (U = 12238.5, z = 2.473, p = 0.013), diagnosis and symptom measures were not retained as significant predictors in the final robust linear model. Participants scoring higher on agreeableness, extraversion, and openness to experience reported significantly lower anhedonia. These results demonstrate personality as a mild-to-moderate but significant driver of differences in experiencing pleasure in a community sample.

The amygdala-ventral pallidum pathway contributes to a hypodopaminergic state in the ventral tegmental area during protracted abstinence from chronic cocaine

BACKGROUND AND PURPOSE

Incubation of craving, the progressive increase in drug seeking over the first weeks of abstinence, is associated with temporal changes during abstinence in the activity of several structures involved in drug-seeking behaviour. Decreases of dopamine (DA) release and DA neuronal activity (hypodopaminergic state) have been reported in the ventral tegmental area (VTA) during cocaine abstinence, but the mechanisms underlying these neuroadaptations are not well understood. We investigated the potential involvement of a VTA inhibiting circuit (basolateral amygdala [BLA]-ventral pallidum [VP] pathway) in the hypodopaminergic state associated with abstinence from chronic cocaine.

EXPERIMENTAL APPROACH

In a model of cocaine self-administration, we performed in vivo electrophysiological recordings of DA VTA neurons and BLA neurons from anaesthetised rats during early and protracted abstinence and evaluated the involvement of the BLA-VP pathway using a pharmacological approach.

KEY RESULTS

We found significant decreases in VTA DA population activity and significant increases in BLA activity after protracted but not after short-term abstinence from chronic cocaine. The decrease in VTA DA activity was restored by pharmacological inhibition of the activity of either the BLA or the VP, suggesting that these regions exert a negative influence on DA activity.

CONCLUSION AND IMPLICATIONS

Our study sheds new lights on neuroadaptations occurring during incubation of craving leading to relapse. In particular, we describe the involvement of the BLA-VP pathway in cocaine-induced decreases of DA activity in the VTA. This study adds important information about the specific brain network dysfunctions underlying hypodopaminergic activity during abstinence.

Anhedonia as a transdiagnostic symptom across psychological disorders: a network approach

BACKGROUND

Anhedonia is apparent in different mental disorders and is suggested to be related to dysfunctions in the reward system and/or affect regulation. It may hence be a common underlying feature associated with symptom severity of mental disorders.

METHODS

We constructed a cross-sectional graphical Least Absolute Shrinkage and Selection Operator (LASSO) network and a relative importance network to estimate the relationships between anhedonia severity and the severity of symptom clusters of major depressive disorder (MDD), anxiety sensitivity (AS), attention-deficit hyperactivity disorder (ADHD), and autism spectrum disorder (ASD) in a sample of Dutch adult psychiatric patients (N = 557).

RESULTS

Both these networks revealed anhedonia severity and depression symptom severity as central to the network. Results suggest that anhedonia severity may be predictive of the severity of symptom clusters of MDD, AS, ADHD, and ASD. MDD symptom severity may be predictive of AS and ADHD symptom severity.

CONCLUSIONS

The results suggest that anhedonia may serve as a common underlying transdiagnostic psychopathology feature, predictive of the severity of symptom clusters of depression, AS, ADHD, and ASD. Thus, anhedonia may be associated with the high comorbidity between these symptom clusters and disorders. If our results will be replicated in future studies, it is recommended for clinicians to be more vigilant about screening for anhedonia and/or depression severity in individuals diagnosed with an anxiety disorder, ADHD and/or ASD.

Transdiagnostic Approach and Obsessive Compulsive Disorder

The categorical approach of traditional psychiatric nosology has been a forceful approach for a very long time for explaining psychological disorders which are defined by symptom based diagnostic categories. However, in recent years, the importance of the "transdiagnostic" approach which is a new classification system is increasing. The transdiagnostic approach aims to examine dimensionally the common cognitive, behavioral, interpersonal and biological processes underlying many psychopathologies away from the categorical approach that classifies psychopathologies according to observable symptoms. This approach intends to treat the disorders through the common underlying processes and risk factors, thus heterogeneous and comorbid symptoms are better addressed and diagnostic categories that may change during treatment are avoided. In this review study, the current problems in diagnosing based on classification and gaps in the field were examined, and the approach itself was proposed as a solution. RDoC (Research Domain Criteria) which is a new classification system for psychiatric disorders within the scope of the approach, has created a new structure using modern research approaches in genetics, neuroscience and behavioral sciences. In the present study, the definition and emergence of the transdiagnostic approach, obsessive compulsive disorder and RDoC in the context of transdiagnostic approach and transdiagnostic treatment are explained. This review is intended to be a resource for both basic psychopathology research and the development of treatment methods within the framework of a transdiagnostic approach.

Treatment with the second-generation antipsychotic quetiapine is associated with increased subgenual ACC activation during reward processing in major depressive disorder

BACKGROUND

The second-generation antipsychotic (SGA) quetiapine is an essential option for antidepressant augmentation therapy in major depressive disorder (MDD), yet neurobiological mechanisms behind its antidepressant properties remain unclear. As SGAs interfere with activity in reward-related brain areas, including the anterior cingulate cortex (ACC) - a key brain region in antidepressant interventions, this study examined whether quetiapine treatment affects ACC activity during reward processing in MDD patients.

METHODS

Using the ACC as region of interest, an independent t-test comparing reward-related BOLD response of 51 quetiapine-taking and 51 antipsychotic-free MDD patients was conducted. Monetary reward outcome feedback was measured in a card-guessing paradigm using pseudorandom blocks. Participants were matched for age, sex, and depression severity and analyses were controlled for confounding variables, including total antidepressant medication load, illness chronicity and acute depression severity. Potential dosage effects were examined in a 3 × 1 ANOVA. Differences in ACC-related functional connectivity were assessed in psycho-physiological interaction (PPI) analyses.

RESULTS

Left subgenual ACC activity was significantly higher in the quetiapine group compared to antipsychotic-free participants and dependent on high-dose quetiapine intake. Results remained significant after controlling for confounding variables. The PPI analysis did not yield significant group differences in ACC-related functional connectivity.

LIMITATIONS

Causal interpretation is limited due to cross-sectional findings.

CONCLUSION

Elevated subgenual ACC activity to rewarding stimuli may represent a neurobiological marker and potential key interface of quetiapine's antidepressant effects in MDD. These results underline ACC activity during reward processing as an investigative avenue for future research and therapeutic interventions to improve MDD treatment outcomes.

"Don't [ruminate], be happy": A cognitive perspective linking depression and anhedonia

Anhedonia, a lack of pleasure in things an individual once enjoyed, and rumination, the process of perseverative and repetitive attention to specific thoughts, are hallmark features of depression. Though these both contribute to the same debilitating disorder, they have often been studied independently and through different theoretical lenses (e.g., biological vs. cognitive). Cognitive theories and research on rumination have largely focused on understanding negative affect in depression with much less focus on the etiology and maintenance of anhedonia. In this paper, we argue that by examining the relation between cognitive constructs and deficits in positive affect, we may better understand anhedonia in depression thereby improving prevention and intervention efforts. We review the extant literature on cognitive deficits in depression and discuss how these dysfunctions may not only lead to sustained negative affect but, importantly, interfere with an ability to attend to social and environmental cues that could restore positive affect. Specifically, we discuss how rumination is associated to deficits in working memory and propose that these deficits in working memory may contribute to anhedonia in depression. We further argue that analytical approaches such as computational modeling are needed to study these questions and, finally, discuss implications for treatment.

Anhedonia modulates benzodiazepine and opioid demand among persons in treatment for opioid use disorder

Background

Benzodiazepine (BZD) misuse is a significant public health problem, particularly in conjunction with opioid use, due to increased risks of overdose and death. One putative mechanism underlying BZD misuse is affective dysregulation, via exaggerated negative affect (e.g., anxiety, depression, stress-reactivity) and/or impaired positive affect (anhedonia). Similar to other misused substances, BZD consumption is sensitive to price and individual differences. Although purchase tasks and demand curve analysis can shed light on determinants of substance use, few studies have examined BZD demand, nor factors related to demand.

Methods

This ongoing study is examining simulated economic demand for alprazolam (among BZD lifetime misusers based on self-report and DSM-5 diagnosis; n = 23 total; 14 male, 9 female) and each participant's preferred-opioid/route using hypothetical purchase tasks among patients with opioid use disorder (n = 59 total; 38 male, 21 female) who are not clinically stable, i.e., defined as being early in treatment or in treatment longer but with recent substance use. Aims are to determine whether: (1) BZD misusers differ from never-misusers on preferred-opioid economic demand, affective dysregulation (using questionnaire and performance measures), insomnia/behavioral alertness, psychiatric diagnoses or medications, or urinalysis results; and (2) alprazolam demand among BZD misusers is related to affective dysregulation or other measures.

Results

Lifetime BZD misuse is significantly (p < 0.05) related to current major depressive disorder diagnosis, opioid-negative and methadone-negative urinalysis, higher trait anxiety, greater self-reported affective dysregulation, and younger age, but not preferred-opioid demand or insomnia/behavioral alertness. Alprazolam and opioid demand are each significantly positively related to higher anhedonia and, to a lesser extent, depression symptoms but no other measures of negative-affective dysregulation, psychiatric conditions or medications (including opioid agonist therapy or inpatient/outpatient treatment modality), or sleep-related problems.

Conclusion

Anhedonia (positive-affective deficit) robustly predicted increased BZD and opioid demand; these factors could modulate treatment response. Routine assessment and effective treatment of anhedonia in populations with concurrent opioid and sedative use disorder may improve treatment outcomes.

Clinical trial registration

https://clinicaltrials.gov/ct2/show/NCT03696017, identifier NCT03696017.

[Anhedonia in mood disorders and somatic diseases: results of exploratory Mendelian randomization analysis]

OBJECTIVE

To conduct an exploratory Mendelian randomization analysis of the causal relationships of anhedonia with a wide range of psychiatric and somatic phenotypes based on the genetic data of participants in a population study.

MATERIAL AND METHODS

This cross-sectional study included 4520 participants, of which 50.4% (n=2280) were female. The mean age was 36.8 (S.D.=9.8) years. Participants were pheno-nailed based on the DSM-5 criteria for anhedonia in the framework of depression. An episode of anhedonia exceeding 2 weeks during life was reported by 57.6% (n=2604) of participants. A genome-wide association study (GWAS) of the anhedonia phenotype was performed, as well as a Mendelian randomization analysis using summary statistics of large-scale GWASs on psychiatric and somatic phenotypes.

RESULTS

The GWAS on anhedonia did not reveal the variants with genome-wide significant association (p<10^-8). The most significant (p=9.71×10^-7) was the variant rs296009 (chr5:168513184) in an intron of the slit guidance ligand 3 (SLIT3) gene. Using Mendelian randomization, nominally significant (p<0.05) causal associations of anhedonia with 24 phenotypes were identified, which can be divided into 5 main groups: psychiatric/neurological diseases, inflammatory diseases of the digestive system, respiratory diseases, oncological diseases and metabolic disorders. The most significant causal effects of anhedonia were found for breast cancer (p=0.0004, OR=0.9986, 95% confidence interval (CI) (0.9978-0.999)), minimal depression phenotype (p=0.009, OR=1.004, 95% CI (1.001-1.007)), as well as for apolipoprotein A (p=0.01, OR=0.973, 95% CI (0.952-0.993)) and respiratory diseases (p=0.01, OR=0.9988, 95% CI (0.9980-0.9997)).

CONCLUSION

The polygenic nature of anhedonia may cause the risks of comorbidity of this phenotype with a wide range of somatic diseases, as well as may be associated with mood disorders.

Sex differences in addiction-relevant behavioral outcomes in rodents following early life stress

In humans, exposure to early life stress (ELS) is an established risk factor for the development of substance use disorders (SUDs) during later life. Similarly, rodents exposed to ELS involving disrupted mother-infant interactions, such as maternal separation (MS) or adverse caregiving due to scarcity-adversity induced by limited bedding and nesting (LBN) conditions, also exhibit long-term alterations in alcohol and drug consumption. In both humans and rodents, there is a range of addiction-related behaviors that are associated with drug use and even predictive of subsequent SUDs. In rodents, these include increased anxiety-like behavior, impulsivity, and novelty-seeking, altered alcohol and drug intake patterns, as well as disrupted reward-related processes involving consummatory and social behaviors. Importantly, the expression of these behaviors often varies throughout the lifespan. Moreover, preclinical studies suggest that sex differences play a role in how exposure to ELS impacts reward and addiction-related phenotypes as well as underlying brain reward circuitry. Here, addiction-relevant behavioral outcomes and mesolimbic dopamine (DA) dysfunction resulting from ELS in the form of MS and LBN are discussed with a focus on age- and sex-dependent effects. Overall, these findings suggest that ELS may increase susceptibility for later life drug use and SUDs by interfering with the normal maturation of reward-related brain and behavioral function.

Neurosteroids (allopregnanolone) and alcohol use disorder: From mechanisms to potential pharmacotherapy

Alcohol Use Disorder (AUD) is a multifaceted relapsing disorder that is commonly comorbid with psychiatric disorders, including anxiety. Alcohol exposure produces a plethora of effects on neurobiology. Currently, therapeutic strategies are limited, and only a few treatments - disulfiram, acamprosate, and naltrexone - are available. Given the complexity of this disorder, there is a great need for the identification of novel targets to develop new pharmacotherapy. The GABAergic system, the primary inhibitory system in the brain, is one of the well-known targets for alcohol and is responsible for the anxiolytic effects of alcohol. Interestingly, GABAergic neurotransmission is fine-tuned by neuroactive steroids that exert a regulatory role on several endocrine systems involved in neuropsychiatric disorders including AUD. Mounting evidence indicates that alcohol alters the biosynthesis of neurosteroids, whereas acute alcohol increases and chronic alcohol decreases allopregnanolone levels. Our recent work highlighted that chronic alcohol-induced changes in neurosteroid levels are mediated by epigenetic modifications, e.g., DNA methylation, affecting key enzymes involved in neurosteroid biosynthesis. These changes were associated with changes in GABAA receptor subunit expression, suggesting an imbalance between excitatory and inhibitory signaling in AUD. This review will recapitulate the role of neurosteroids in the regulation of the neuroendocrine system, highlight their role in the observed allostatic load in AUD, and develop a framework from mechanisms to potential pharmacotherapy.

Sucrose Preference Test as a Measure of Anhedonic Behavior in a Chronic Unpredictable Mild Stress Model of Depression: Outstanding Issues

Despite numerous studies on the neurobiology of depression, the etiological and pathophysiological mechanisms of this disorder remain poorly understood. A large number of animal models and tests to evaluate depressive-like behavior have been developed. Chronic unpredictable mild stress (CUMS) is the most common and frequently used model of depression, and the sucrose preference test (SPT) is one of the most common tests for assessing anhedonia. However, not all laboratories can reproduce the main effects of CUMS, especially when this refers to a decrease in sucrose preference. It is also unknown how the state of anhedonia, assessed by the SPT, relates to the state of anhedonia in patients with depression. We analyzed the literature available in the PubMed database using keywords relevant to the topic of this narrative review. We hypothesize that the poor reproducibility of the CUMS model may be due to differences in sucrose consumption, which may be influenced by such factors as differences in sucrose preference concentration threshold, water and food deprivation, and differences in animals’ susceptibility to stress. We also believe that comparisons between animal and human states of anhedonia should be made with caution because there are many inconsistencies between the two, including in assessment methods. We also tried to offer some recommendations that should improve the reproducibility of the CUMS model and provide a framework for future research.

A review of functional brain differences predicting relapse in substance use disorder: Actionable targets for new methods of noninvasive brain stimulation

Neuroimaging studies have identified a variety of brain regions whose activity predicts substance use (i.e., relapse) in patients with substance use disorder (SUD), suggesting that malfunctioning brain networks may exacerbate relapse. However, this knowledge has not yet led to a marked improvement in treatment outcomes. Noninvasive brain stimulation (NIBS) has shown some potential for treating SUDs, and a new generation of NIBS technologies offers the possibility of selectively altering activity in both superficial and deep brain structures implicated in SUDs. The goal of the current review was to identify deeper brain structures involved in relapse to SUD and give an account of innovative methods of NIBS that might be used to target them. Included studies measured fMRI in currently abstinent SUD patients and tracked treatment outcomes, and fMRI results were organized with the framework of the Addictions Neuroclinical Assessment (ANA). Four brain structures were consistently implicated: the anterior and posterior cingulate cortices, ventral striatum and insula. These four deeper brain structures may be appropriate future targets for the treatment of SUD using these innovative NIBS technologies.

Is Stress Taking the Pleasure out of Food?—A Characterization of the Food Pleasure Profiles, Appetite, and Eating Behaviors of People with Chronic Stress

Psychological stressors frequently occur in modern society, and are associated with general anhedonic traits (inability to experience pleasure) and altered eating behavior. As eating behavior is largely motivated by a desire for pleasure, the Food Pleasure Scale (FPS) was introduced as a new research tool for investigating aspects of pleasure from food-related experiences. Thereby, insights on whether some aspects of pleasure are more affected by stress than others can be investigated, and can help explain why changes in eating behavior are seen when under the influence of stress. A consumer survey including n = 190 Danish consumers all with moderate or high levels of perceived stress was conducted to explore the perception of pleasure from food, general appetite, meal patterns, as well as specific food preferences. The study showed that the majority found pleasure in the sensory modalities of food, as well as in the ‘comforting’ aspects of food pleasure. Furthermore, the moderately stressed respondents had fewer main meals and more post-dinner snacks and night meals, as compared to before falling ill, whereas the highly stressed group showed signs of anhedonic traits and losing appetite altogether. The present study contributes to our understanding of how a common condition, such as chronic stress, can affect individual, as well as public, health.

Chronic Physical and Vicarious Psychosocial Stress Alter Fentanyl Consumption and Nucleus Accumbens Rho GTPases in Male and Female C57BL/6 Mice

Chronic stress can increase the risk of developing a substance use disorder in vulnerable individuals. Numerous models have been developed to probe the underlying neurobiological mechanisms, however, most prior work has been restricted to male rodents, conducted only in rats, or introduces physical injury that can complicate opioid studies. Here we sought to establish how chronic psychosocial stress influences fentanyl consumption in male and female C57BL/6 mice. We used chronic social defeat stress (CSDS), or the modified vicarious chronic witness defeat stress (CWDS), and used social interaction to stratify mice as stress-susceptible or resilient. We then subjected mice to a 15 days fentanyl drinking paradigm in the home cage that consisted of alternating forced and choice periods with increasing fentanyl concentrations. Male mice susceptible to either CWDS or CSDS consumed more fentanyl relative to unstressed mice. CWDS-susceptible female mice did not differ from unstressed mice during the forced periods, but showed increased preference for fentanyl over time. We also found decreased expression of nucleus accumbens Rho GTPases in male, but not female mice following stress and fentanyl drinking. We also compare fentanyl drinking behavior in mice that had free access to plain water throughout. Our results indicate that stress-sensitized fentanyl consumption is dependent on both sex and behavioral outcomes to stress.

Social Isolation-Mediated Exacerbation of Negative Affect in Young Drinkers during the COVID-19 Pandemic

Emerging research on psychological adjustment during the COVID-19 outbreak has suggested that young people may be particularly vulnerable to increases in negative affect during the pandemic. However, the association between alcohol use in youth and change in negative affect during this unprecedented time is not clear. Using an online survey, this study obtained scores on negative affect (before and during the COVID-19 pandemic), pandemic-related stress, change in drinking frequency, and traits including resilience, impulsivity and anhedonia, from a sample of drinkers and non-drinkers, up to the age of 21. Young drinkers experienced a greater increase in negative affect during the pandemic compared to non-drinkers, and this differential rise in negative affect was mediated by the pandemic-related stress of social isolation. Young drinkers also experienced a decrease in alcohol use during the pandemic, but this was not associated with a change in negative affect. Interestingly, young drinkers with greater resilience and lower anhedonia reported less increase in negative affect during the COVID-19 pandemic. Taken together, these results show that the greater increase in negative affect that young drinkers experienced during the COVID-19 pandemic, compared to their non-drinking counterparts, was mediated by pandemic-related social isolation. Moreover, greater resilience and lower anhedonia may have served as protective factors for mitigating the social isolation-induced worsening of negative affect in young drinkers during the pandemic. These findings may inform future studies investigating potential indicators of maladaptive affective responses to public health crises in vulnerable adolescent populations.

Negative symptoms in alcohol use disorder: A pilot study applying the two-factor model of negative symptoms to patients with alcohol use disorder

BACKGROUND AND AIMS

Alcohol Use Disorder (AUD) is characterized by a reduction in goal-directed behavior, with alcohol use taking precedence over other areas of life. These features in AUD resemble negative symptoms in schizophrenia, especially the reduction in motivation and pleasure (MAP). Given the clinical similarities of negative symptoms across diagnostic categories, it comes as a surprise that there are few investigations on negative symptoms in alcohol and other substance use disorders. To our knowledge, our study is the first to assess negative symptoms in AUD based on a two-factorial approach, and to investigate the interrelation of these dimensions with the severity of AUD, and alcohol craving.

MATERIALS AND METHODS

We examined a sample of 42 patients with AUD at the Psychiatric University Hospital in Zurich. Participants provided self-report and interview-based measures of the severity of AUD, negative symptoms, and alcohol craving. Finally, we used data from the electronic health records of the patients.

RESULTS

Patients with AUD show negative symptoms to a similar extent as patients with schizophrenia or bipolar disorder. We found a positive correlation between the extent of impairment within the MAP factor and overall severity of AUD. Furthermore, MAP negative symptoms were correlated with alcohol craving. In a linear regression, negative symptoms predicted alcohol craving whereas depression did not.

SUMMARY

Negative symptoms as conceptualized for schizophrenia are prevalent in patients with AUD and associated with the severity of AUD. More specifically, severity of AUD correlates with diminished motivation and pleasure, highlighting the importance of disturbances in motivational functions in AUD. This is further supported by the correlation between negative symptoms and craving, a hallmark of AUD. Taken together, our findings suggest that negative symptoms might be a highly relevant but hitherto often neglected therapeutic target in AUD.

Toward a Quantification of Anhedonia: Unified Matching Law and Signal Detection for Clinical Assessment and Drug Development

Anhedonia, the loss of pleasure from previously rewarding activities, is a core symptom of several neuropsychiatric conditions, including major depressive disorder (MDD). Despite its transdiagnostic relevance, no effective therapeutics exist to treat anhedonia. This is due, in part, to inconsistent assays across clinical populations and laboratory animals, which hamper treatment development. To bridge this gap, recent work has capitalized on two long-standing research domains dedicated to quantifying responsivity to antecedents and consequences across species: the generalized matching law and signal detection theory. This review traces the integration of these quantitative frameworks, which yielded two empirically derived metrics: response bias (log b) and task discriminability (log d). These metrics serve as primary dependent variables in the Probabilistic Reward Task (PRT). In this computerized task, subjects make visual discriminations and probabilistic contingencies are arranged such that correct responses to one alternative are rewarded more often (rich) than correct responses to the other (lean). Under these conditions, healthy participants consistently develop a response bias in favor of the rich alternative, whereas participants with MDD exhibit blunted biases, which correlate with current and predict future anhedonia. Given the correspondence between anhedonic phenotypes and response bias, the PRT has been reverse-translated for rodents and nonhuman primates. Orderly log b and log d values have been observed across diverse clinical populations and laboratory animals. In addition, pharmacological challenges have produced similar outcomes across species. Taken together, this quantitative framework offers a highly translational approach to assaying reward responsiveness to accelerate treatment development for neuropsychiatric disorders involving anhedonia.

The acute and non-acute effects of cannabis on reward processing: A systematic review

Cannabis use has historically been thought to cause amotivation, but the relationship between cannabis and apathy, anhedonia, and reward processing remains poorly characterised. In this systematic review, we evaluated whether cannabis exposure acutely and/or non-acutely was associated with altered reward processing using questionnaire, behavioural, or functional neuroimaging measures. Questionnaire studies demonstrated greater anhedonia in adolescent cannabis users, and some indication of greater apathy in young adult cannabis users. Behavioural studies yielded some evidence of reduced reward learning in adolescent cannabis users, though there were too few studies in this category for reliable conclusions. Finally, longitudinal and acute functional neuroimaging studies showed an association between cannabis and blunted neural responses to reward, which did not emerge consistently in cross-sectional studies. The current results suggest that cannabis use is associated with specific impairments in reward and motivation. Future large-scale, longitudinal studies which use multiple behavioural and neuroimaging measures of reward processing may further clarify the impact of cannabis use on motivational and reward processes, and neural networks.

Anhedonia in tobacco withdrawal among African-American smokers

Anhedonia-diminished interest and pleasure in response to rewards-may be a symptom of tobacco withdrawal that is understudied in priority populations. This experiment investigated the magnitude and correlates of various dimensions of anhedonia during tobacco withdrawal among African-American (AA) smokers-a population subject to health disparities. AA smokers (N = 607; ≥ 10 cigarettes/day, 37.8% female, M[SD] age = 50.0[10.6] years) completed self-report measures assessing expected pleasure from (i.e., consummatory anhedonia) and desire to engage in (i.e., anticipatory anhedonia) various types of hypothetically experienced rewards at counterbalanced 16-hr tobacco deprived and nondeprived lab visits. Other tobacco withdrawal symptom measures (e.g., craving, negative affect, hunger) were also assessed. Tobacco deprivation most robustly increased scores on a composite measure of consummatory anhedonia directed toward various reward domains (i.e., hobbies, sensory experiences, social activities; d = .32, p < .001). Deprivation modestly increased consummatory and anticipatory anhedonia directed toward sexual rewards (ds = .09-.12, ps < .02), did not significantly change anhedonia toward food rewards, and decreased anhedonia directed toward psychoactive drug rewards (i.e., increased desire for and pleasure from drugs; ds = -.21 to -.19, ps < .001). Deprivation-induced changes in anhedonia were modestly correlated with other withdrawal symptoms (average |r|s = .04-.23) and were amplified among participants with higher nicotine dependence and lower positive affect-related traits (|β|s = .10-.12, ps < .01). Some dimensions of anhedonia may be genuine expressions of acute tobacco withdrawal in AA smokers. Applying multi-dimensional anhedonia conceptualizations might advance basic knowledge and treatment of tobacco use disorder, improve smoking cessation outcomes, and address tobacco-related health disparities facing AA smokers. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Posttraumatic stress symptom clusters differentially predict late positive potential to cocaine imagery cues in trauma-exposed adults with cocaine use disorder

BACKGROUND

While studies have investigated the effects of posttraumatic stress disorder (PTSD) symptoms on substance use, information on these associations in the context of drug cue reactivity is lacking, which can provide meaningful information about risk for relapse. The current study assessed the associations between PTSD symptom clusters and reactivity to cues in trauma-exposed adults with cocaine use disorder.

METHODS

We recorded electroencephalogram on 52 trauma-exposed participants (M_age = 51.3; SD = 7.0; 15.4 % women) diagnosed with cocaine use disorder while they viewed pleasant (i.e., erotic, romantic, sweet foods), unpleasant (i.e., mutilations, violence, accidents), neutral, and cocaine-related images. Reactivity was measured with the late positive potential (LPP), an indicator of motivational relevance. It was hypothesized that individuals with greater PTSD avoidance and negative alterations in cognition and mood (NACM) symptoms, as determined by the PTSD Checklist for DSM-5 (PCL-5), would have higher LPPs to cocaine-related images, indicating greater cue reactivity.

RESULTS

Linear mixed modeling indicated that higher NACM symptomatology was associated with higher LPPs to cocaine cues and higher arousal/reactivity was associated with lower LPPs to cocaine cues.

CONCLUSIONS

These results highlight the potential clinical utility of the LPP in assessing drug cue reactivity in trauma-exposed adults with substance use disorder.

I feel good? Anhedonia might not mean "without pleasure" for people treated for opioid use disorder

Anhedonia is usually defined as partial or total loss of the capacity for pleasure. People with anhedonia in the context of major depressive disorder may have an unexpected capacity for event-related mood brightening, observable when mood is assessed dynamically (with smartphone-based ecological momentary assessment [EMA]) rather than only statically via questionnaire. We used EMA to monitor mood and pleasant events for 4 weeks in 54 people being treated with opioid agonist medication for opioid-use disorder (OUD), which is also associated with anhedonia, said to manifest especially as loss of pleasure from nondrug reward. We compared OUD patients' EMA reports with those of 47 demographically similar controls. Background positive mood was lower in OUD patients than in controls, as we hypothesized (Cohen ds = .85 to 1.32, 95% CIs [.66, 1.55]), although, contrary to our hypothesis, background negative mood was also lower (ds = .82 to .85, 95% CIs [.73, .94]). As hypothesized, instances of nondrug pleasure were as frequent in OUD patients as in controls-and were not rated much less pleasurable (d = .18, 95% CI [-.03, .35]). Event-related mood brightening occurred in both abstinent and nonabstinent OUD patients (ds = .18 to .37, CIs [-.01, .57]) and controls (ds = .04 to .60, CIs [-.17, .79]), brightening before each event began earlier for controls than OUD patients, but faded similarly postevent across groups. Our findings add to the evidence that anhedonia does not rule out reactive mood brightening, which, for people with OUD being treated on opioid agonist medication, can be elicited by nondrug activities. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Anhedonia as a central factor in depression: Neural mechanisms revealed from preclinical to clinical evidence

Anhedonia is one of the core symptoms of major depressive disorder (MDD), which is often inadequately treated by traditional antidepressants. The modern framework of anhedonia extends the definition from impaired consummatory pleasure or interest in rewards to a broad spectrum of deficits that impact functions such as reward anticipation, approach motivation, effort expenditure, reward valuation, expectation, and reward-cue association learning. Substantial preclinical and clinical research has explored the neural basis of reward deficits in the context of depression, and has implicated mesocorticolimbic reward circuitry comprising the nucleus accumbens, ventral pallidum, ventral tegmental area, amygdala, hippocampus, anterior cingulate, insula, orbitofrontal cortex, and other prefrontal cortex regions. Dopamine modulates several reward facets including anticipation, motivation, effort, and learning. As well, serotonin, norepinephrine, opioids, glutamate, Gamma aminobutyric acid (GABA), and acetylcholine are also involved in anhedonia, and medications targeting these systems may also potentially normalize reward processing in depression. Unfortunately, whereas reward anticipation and reward outcome are extensively explored by both preclinical and clinical studies, translational gaps remain in reward motivation, effort, valuation, and learning, where clinical neuroimaging studies are in the early stages. This review aims to synthesize the neurobiological mechanisms underlying anhedonia in MDD uncovered by preclinical and clinical research. The translational difficulties in studying the neural basis of reward are also discussed.

Neuronal adaptations in the lateral habenula during drug withdrawal: Preclinical evidence for addiction therapy

The epithalamic lateral habenula (LHb) regulates monoaminergic systems and contributes to the expression of both appetitive and aversive behaviours. Over the past years, the LHb has emerged as a vulnerable brain structure in mental illnesses including addiction. Behavioural and functional evidence in humans and rodents provide substantial support for a role of LHb in the negative affective symptoms emerging during withdrawal from addictive substances. Multiple forms of cellular and synaptic adaptations that take hold during drug withdrawal within the LHb are causally linked with the emergence of negative affective symptoms. These results indicate that targeting drug withdrawal-driven adaptations in the LHb may represent a potential strategy to normalize drug-related behavioural adaptations. In the current review we describe the mechanisms leading to functional alterations in the LHb, as well as the existing interventions used to counteract addictive behaviours. Finally, closing this loop we discuss and propose new avenues to potentially target the LHb in humans in light of the mechanistic understanding stemming from pre-clinical studies. Altogether, we provide an overview on how to leverage cellular-level understanding to envision clinically-relevant approaches for the treatment of specific aspects in drug addiction.

Converging vulnerability factors for compulsive food and drug use

Highly palatable foods and substance of abuse have intersecting neurobiological, metabolic and behavioral effects relevant for understanding vulnerability to conditions related to food (e.g., obesity, binge eating disorder) and drug (e.g., substance use disorder) misuse. Here, we review data from animal models, clinical populations and epidemiological evidence in behavioral, genetic, pathophysiologic and therapeutic domains. Results suggest that consumption of highly palatable food and drugs of abuse both impact and conversely are regulated by metabolic hormones and metabolic status. Palatable foods high in fat and/or sugar can elicit adaptation in brain reward and withdrawal circuitry akin to substances of abuse. Intake of or withdrawal from palatable food can impact behavioral sensitivity to drugs of abuse and vice versa. A robust literature suggests common substrates and roles for negative reinforcement, negative affect, negative urgency, and impulse control deficits, with both highly palatable foods and substances of abuse. Candidate genetic risk loci shared by obesity and alcohol use disorders have been identified in molecules classically associated with both metabolic and motivational functions. Finally, certain drugs may have overlapping therapeutic potential to treat obesity, diabetes, binge-related eating disorders and substance use disorders. Taken together, data are consistent with the hypotheses that compulsive food and substance use share overlapping, interacting substrates at neurobiological and metabolic levels and that motivated behavior associated with feeding or substance use might constitute vulnerability factors for one another. This article is part of the special issue on 'Vulnerabilities to Substance Abuse'.

The Role of Mu-Opioids for Reward and Threat Processing in Humans: Bridging the Gap from Preclinical to Clinical Opioid Drug Studies

PURPOSE OF REVIEW

Opioid receptors are widely expressed in the human brain. A number of features commonly associated with drug use disorder, such as difficulties in emotional learning, emotion regulation and anhedonia, have been linked to endogenous opioid signalling. Whereas chronic substance use and misuse are thought to alter the function of the mu-opioid system, the specific mechanisms are not well understood. We argue that understanding exogenous and endogenous opioid effects in the healthy human brain is an essential foundation for bridging preclinical and clinical findings related to opioid misuse. Here, we will examine psychopharmacological evidence to outline the role of the mu-opioid receptor (MOR) system in the processing of threat and reward, and discuss how disruption of these processes by chronic opioid use might alter emotional learning and reward responsiveness.

RECENT FINDINGS

In healthy people, studies using opioid antagonist drugs indicate that the brain's endogenous opioids downregulate fear reactivity and upregulate learning from safety. At the same time, endogenous opioids increase the liking of and motivation to engage with high reward value cues. Studies of acute opioid agonist effects indicate that with non-sedative doses, drugs such as morphine and buprenorphine can mimic endogenous opioid effects on liking and wanting. Disruption of endogenous opioid signalling due to prolonged opioid exposure is associated with some degree of anhedonia to non-drug rewards; however, new results leave open the possibility that this is not directly opioid-mediated.

SUMMARY

The available human psychopharmacological evidence indicates that the healthy mu-opioid system contributes to the regulation of reward and threat processing. Overall, endogenous opioids can subtly increase liking and wanting responses to a wide variety of rewards, from sweet tastes to feelings of being connected to close others. For threat-related processing, human evidence suggests that endogenous opioids inhibit fear conditioning and reduce the sensitivity to aversive stimuli, although inconsistencies remain. The size of effects reported in healthy humans are however modest, clearly indicating that MORs play out their role in close concert with other neurotransmitter systems. Relevant candidate systems for future research include dopamine, serotonin and endocannabinoid signalling. Nevertheless, it is possible that endogenous opioid fine-tuning of reward and threat processing, when unbalanced by e.g. opioid misuse, could over time develop into symptoms associated with opioid use disorder, such as anhedonia and depression/anxiety.

The Developmental Origins of Opioid Use Disorder and Its Comorbidities

Opioid use disorder (OUD) rarely presents as a unitary psychiatric condition, and the comorbid symptoms likely depend upon the diverse risk factors and mechanisms by which OUD can arise. These factors are heterogeneous and include genetic predisposition, exposure to prescription opioids, and environmental risks. Crucially, one key environmental risk factor for OUD is early life adversity (ELA). OUD and other substance use disorders are widely considered to derive in part from abnormal reward circuit function, which is likely also implicated in comorbid mental illnesses such as depression, bipolar disorder, and schizophrenia. ELA may disrupt reward circuit development and function in a manner predisposing to these disorders. Here, we describe new findings addressing the effects of ELA on reward circuitry that lead to OUD and comorbid disorders, potentially via shared neural mechanisms. We discuss some of these OUD-related problems in both humans and animals. We also highlight the increasingly apparent, crucial contribution of biological sex in mediating the range of ELA-induced disruptions of reward circuitry which may confer risk for the development of OUD and comorbid neuropsychiatric disorders.

Housing conditions during self-administration determine motivation for cocaine in mice following chronic social defeat stress

RATIONALE

Stress exposure has a lasting impact on motivated behavior and can exacerbate existing vulnerabilities for developing a substance use disorder. Several models have been developed to examine how stressful experiences shape drug reward. These range from locomotor sensitization and conditioned place preference to the propensity for drug self-administration or responding to drug-predictive cues. While self-administration studies are considered to have more translational relevance, most of the studies to date have been conducted in rats. Further, many self-administration studies are conducted in single-housed animals, adding the additional stressor of social isolation.

OBJECTIVES

We sought to establish how chronic social defeat stress (CSDS) and social housing conditions impact cocaine self-administration and cocaine-seeking behaviors in C57BL/6 mice.

METHODS

We assessed self-administration behavior (cocaine or saline, 0.5 mg/kg/infusion) in C57BL/6 mice subjected to 10-day CSDS or in unstressed controls. Mice were housed either in pairs or in isolation during self-administration. We compared the effect of housing on acquisition of self-administration, seeking, extinction, drug-induced reinstatement, and after re-exposure to the social stressor.

RESULTS

Pair-housing during self-administration revealed increased social avoidance after CSDS is associated with decreased cocaine intake. In contrast, single-housing revealed stress-sensitive cocaine intake, with increased social avoidance after CSDS associated with increased early cocaine intake. Pair-, but not single-housed mice are susceptible to drug-induced reinstatement independent of CSDS history. Stress re-exposure sensitized cocaine-seeking in stressed single-housed mice.

CONCLUSIONS

The social context surrounding cocaine intake can bidirectionally influence cocaine-related behaviors after psychosocial stress and should be considered when studying stress and drug cross-sensitization.

The Association between Reward Sensitivity and Activity Engagement: the Influence of Delay Discounting and Anhedonia

Aim

Reward sensitivity affects individuals’ motivation to engage in goal-directed behavior. Other concepts, critical for reward appraisal, that potentially influence activity participation encompass delay discounting and anhedonia. The aim of this study was to test the hypothesis that anhedonia and delay discounting influence the relationship between reward sensitivity and activity engagement.

Methods

In total, 37 inpatient patients with an alcohol use disorder (AUD) and 37 matched healthy controls completed the behavioral activation system scale (BAS scale), the Pleasant Activities List (PAL), the Snaith–Hamilton Pleasure Scale (SHAPS) and the Delay Discounting Task (DDT).

Results

Patients differed from controls on SHAPS, DDT-k, PAL substance-related activities (SRA), but not BAS and PAL non-substance-related activities (non-SRA). Correlational analyses revealed a strong correlation between BAS and PAL non-SRA in both patients (r = 0.53) and controls (r = 0.47), but also with PAL-SRA in patients (r = 0.40), although not controls (r = 0.09). BAS was negatively correlated with SHAPS in both groups and with DDT in controls. SHAPS was negatively linked to PAL non-SRA in both groups. The BAS-PAL non-SRA relationship was influenced by discount rates in controls.

Conclusion

A strong link exists between reward sensitivity and engagement in non-SRA in both groups. Delay discounting affects the reward sensitivity and non-SRA association in healthy controls, while anhedonia did not impact the association between reward sensitivity and engagement in (non-)SRA in both conditions.

The effects of early life stress on motivated behaviors: A role for gonadal hormones

Motivated behaviors are controlled by the mesocorticolimbic dopamine (DA) system, consisting of projections from the ventral tegmental area (VTA) to the nucleus accumbens (NAc) and prefrontal cortex (PFC), with input from structures including the medial preoptic area (mPOA). Sex differences are present in this circuit, and gonadal hormones (e.g., estradiol and testosterone) are important for regulating DA transmission. Early life stress (ELS) also regulates the mesocorticolimbic DA system. ELS modifies motivated behaviors and the underlying DA circuitry, increasing risk for disorders such as substance use disorder, major depression, and schizophrenia. ELS has been shown to change gonadal hormone signaling in both sexes. Thus, one way that ELS could impact mesocorticolimbic DA is by altering the efficacy of gonadal hormones. This review provides evidence for this idea by integrating the gonadal hormone, motivation, and ELS literature to argue that ELS alters gonadal hormone signaling to impact motivated behavior. We also discuss the importance of these effects in the context of understanding risk and treatments for psychiatric disorders in men and women.

Relevance of routine activities for understanding the impact of the dual systems model on binge drinking among college students

BACKGROUND

Past research has indicated that dual systems model constructs (impulsivity, sensation-seeking) are predictors of binge drinking. Further, engagement in routine unstructured social activities also predicts elevated risk for binge drinking. However, there has yet to be any research that examines the interactive effect of these constructs.

METHODS

The present study utilized a sample of 248 undergraduate students to understand the relationships between concepts on interest. A series of ordinal logistic regression models were estimated to determine the direct effects of impulsivity, sensation-seeking, and routine activities on binge drinking and also determine whether or not involvement in routine activities moderated the direct effects of either impulsivity and/or sensation-seeking on binge drinking.

RESULTS

Results indicated that lower sensation-seeking was associated with elevated binge drinking frequency. However, the interaction between routine activities and sensation-seeking indicated a positive relationship. This meant that the effects of high levels of sensation-seeking on binge drinking were exacerbated at higher levels of routine activities involvement.

CONCLUSIONS

Findings of the present study indicate that students high in sensation-seeking and engagement in unstructured socializing present great risk for high frequency binge drinking. However, students who demonstrate low levels of sensation-seeking may also present an at-risk population, as they may be using alcohol to self-medicate anhedonia symptoms.

Assessment of Anhedonia in Adults With and Without Mental Illness: A Systematic Review and Meta-analysis

IMPORTANCE

Anhedonia, a reduced capacity for pleasure, is described for many psychiatric and neurologic conditions. However, a decade after the Research Domain Criteria launch, whether anhedonia severity differs between diagnoses is still unclear. Reference values for hedonic capacity in healthy humans are also needed.

OBJECTIVE

To generate and compare reference values for anhedonia levels in adults with and without mental illness.

DATA SOURCES

Web of Science, Scopus, PubMed, and Google Scholar were used to list all articles from January 1, 1995 to July 2, 2019, citing the scale development report of a widely used anhedonia questionnaire, the Snaith-Hamilton Pleasure Scale (SHAPS). Searches were conducted from April 5 to 11, 2018, and on July 2, 2019.

STUDY SELECTION

Studies including healthy patients and those with a verified diagnosis, assessed at baseline or in a no-treatment condition with the complete 14-item SHAPS, were included in this preregistered meta-analysis.

DATA EXTRACTION AND SYNTHESIS

Random-effects models were used to calculate mean SHAPS scores and 95% CIs separately for healthy participants and patients with current major depressive disorder (MDD), past/remitted MDD, bipolar disorder, schizophrenia, substance use disorders, Parkinson disease, and chronic pain. SHAPS scores were compared between groups using meta-regression, and traditional effect size meta-analyses were conducted to estimate differences in SHAPS scores between healthy and patient samples. This study followed the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines.

MAIN OUTCOMES AND MEASURES

Self-reported anhedonia as measured by 2 different formats of the SHAPS (possible ranges, 0-14 and 14-56 points), with higher values on both scales indicating greater anhedonia symptoms.

RESULTS

In the available literature (168 articles; 16 494 participants; 8058 [49%] female participants; aged 13-72 years), patients with current MDD, schizophrenia, substance use disorder, Parkinson disease, and chronic pain scored higher on the SHAPS than healthy participants. Within the patient groups, those with current MDD scored considerably higher than all other groups. Patients with remitted MDD scored within the healthy range (g = 0.1). This pattern replicated across SHAPS scoring methods and was consistent across point estimate and effect size analyses.

CONCLUSIONS AND RELEVANCE

The findings of this meta-analysis indicate that the severity of anhedonia may differ across disorders associated with anhedonia. Whereas anhedonia in MDD affects multiple pleasure domains, patients with other conditions may experience decreased enjoyment of only a minority of life's many rewards. These findings have implications for psychiatric taxonomy development, where dimensional approaches are gaining attention. Moreover, the SHAPS reference values presented herein may be useful for researchers and clinicians assessing the efficacy of anhedonia treatments.

Chronic Intermittent Ethanol Exposure Increases Ethanol Consumption Following Traumatic Stress Exposure in Mice

Individuals with post-traumatic stress disorder (PTSD) often use alcohol to cope with their distress. This aberrant use of alcohol often develops into alcohol use disorder (AUD) leading to high rates of PTSD-AUD co-occurrence. Individuals with comorbid PTSD-AUD have more intense alcohol cravings and increased relapse rates during withdrawal than those with AUD alone. Also, individuals with PTSD or AUD alone often show similar psychological behaviors, such as impulsivity and anhedonia. Extensive clinical studies on the behavioral effects of PTSD-AUD comorbidity, namely alcohol use, have been performed. However, these effects have not been well studied or mechanistically explored in animal models. Therefore, the present study evaluated the effects of traumatic stress comorbid with alcohol exposures on ethanol intake, impulsivity, and anhedonia in mice. Adult male C57Bl/6 mice were first exposed to either mouse single-prolonged stress (mSPS), an animal model that has been validated for characteristics akin to PTSD symptoms, or control conditions. Baseline two-bottle choice ethanol consumption and preference tests were conducted after a 7-day isolation period, as part of the mSPS exposure. Next, mice were exposed to air or chronic intermittent ethanol (CIE), a vapor-induced ethanol dependence and withdrawal model, for 4 weeks. Two-bottle choice ethanol drinking was used to measure dependence-induced ethanol consumption and preference during periods intervening CIE cycles. The novelty suppressed feeding (NSF) test was used to evaluate impulsivity and anhedonia behaviors 48 h after mSPS and/or repeated CIE exposure. Results showed that, compared to control conditions, mSPS did not affect baseline ethanol consumption and preference. However, mSPS-CIE mice increased Post-CIE ethanol consumption compared to Control-Air mice. Mice exposed to mSPS had a shorter latency to feed during the NSF, whereas CIE-exposed mice consumed less palatable food reward in their home cage after the NSF. These results demonstrate that mice exposed to both mSPS and CIE are more vulnerable to ethanol withdrawal effects, and those exposed to mSPS have increased impulsivity, while CIE exposure increases anhedonia. Future studies to examine the relationship between behavioral outcomes and the molecular mechanisms in the brain after PTSD-AUD are warranted.

R-(-)-ketamine modifies behavioral effects of morphine predicting efficacy as a novel therapy for opioid use disorder1

Substance abuse disorder continues to have devastating consequences for individuals and society and current therapies are not sufficient to provide the magnitude of medical impact required. Although some evidence suggests the use of ketamine in treating various substance use related- symptoms, its adverse event profile including dissociation, dysphoria, and abuse liability limit its potential as a therapy. Here, we outline experiments to test our hypothesis that (R)-ketamine can both alleviate withdrawal symptoms and produce effects that help sustain abstinence. In morphine-dependent rats, (R)-ketamine alleviated naloxone-precipitated withdrawal signs. (R)-ketamine also blocked morphine-induced place preference in mice without inducing place preference on its own. We also evaluated whether (R)-ketamine would induce anhedonia, a counter-indicated effect for a drug abuse treatment agent. S-(+)- but not R-(-)-ketamine produced anhedonia-like responses in rats that electrically self-stimulated the medial forebrain bundle (ICSS). However, time-course studies of ICSS are needed to fully appreciate these differences. These data begin to support the claim that (R)-ketamine will dampen withdrawal symptoms and drug liking, factors known to contribute to the cycle of drug addiction. In addition, these data suggest that (R)-ketamine would not produce negative mood or anhedonia that could interfere with treatment. It is suggested that continued investigation of (R)-ketamine as a novel therapeutic for substance abuse disorder be given consideration by the preclinical and clinical research communities. This suggestion is further encouraged by a recent report on the efficacy of (R)-ketamine in treatment-resistant depressed patients at a dose with little measurable dissociative side-effects.

Substance use disorders and risk for treatment resistant depression: a population-based, nested case-control study

BACKGROUND AND AIMS

Treatment-resistant depression (TRD), defined as inadequate treatment response after at least two adequate treatment trials, is common among patients initiating antidepressant treatment. Current or previous substance use disorders (SUD) are common among patients with depression and often lead to worse treatment outcomes. However, in clinical studies, SUD have not been found to increase the risk for TRD. The aim of this study was to investigate the association between SUD and TRD.

DESIGN

Nested case-control study.

SETTING

Nation-wide governmental health-care registers in Sweden.

CASES AND CONTROLS

Data on prescribed drugs and diagnoses from specialized health care were used to establish a prospectively followed cohort of antidepressant initiators with depression (n = 121 669) from 2006 to 2014. Of these, 15 631 patients (13%) were defined as TRD cases, with at least three treatment trials within a single depressive episode. Each case with TRD was matched on socio-demographic data with five controls with depression.

MEASUREMENTS

Crude and adjusted odds ratios (aOR) with 95% confidence intervals (CI) estimated the association between TRD and SUD diagnosis and/or treatment in five different time intervals until the time for fulfillment of TRD definition for the case. The analysis was adjusted for clinical and socio-demographic covariates.

FINDINGS

Having any SUD during, or ≤ 180 days before start of, antidepressant treatment was associated with almost double the risk for TRD [≤ 180 days before: adjusted OR (aOR) = 1.86, CI = 1.70-2.05]. Increased risks for TRD were found ≤ 180 days before treatment start for the subcategories of sedative use (aOR = 2.37; 1.88-2.99), opioids (aOR = 2.02; 1.48-2.75), alcohol (aOR = 1.77; CI = 1.59-1.98) and combined substance use (aOR = 2.31; 1.87-2.99).

CONCLUSIONS

Recent or current substance use disorders is positively associated with treatment resistance among patients initiating treatment for depression.

Behavioral activation and smoking cessation outcomes: The role of depressive symptoms

INTRODUCTION

Depressive symptoms are related to smoking cessation outcomes. We examined the effects of behavioral activation (BA), as part of a cognitive behavioral intervention to quit smoking, in terms of abstinence rates according to depressive symptom level. We also analyzed whether BA could differentially benefit participants with higher versus lower anhedonia.

METHODS

The sample was composed of 183 smokers (M_age = 45.3; 62.8% female) who participated in a randomized clinical trial assessing the effects of a BA intervention compared to a standard intervention. Smoking outcomes were biochemically confirmed point prevalence abstinence, and abstinence days after treatment during one year follow-up. The intensity of depressive symptomatology and anhedonic symptoms were assessed using the Beck Depression Inventory-II.

RESULTS

No differences in abstinence rates were found in relation to depressive symptom level. The BA condition (vs. standard condition) predicted greater abstinence rates (OR = 1.91) in participants with lower scores on depressive symptoms, whereas in participants with higher scores, it did not (OR = 1.17). Moreover, the BA condition predicted greater abstinence rates in participants with lower scores on anhedonia. When examining days of abstinence during the one-year follow-up period, a significant interaction was found between depressive symptoms and treatment condition, favoring the BA condition.

CONCLUSION

BA implemented as part of a cognitive behavioral intervention to quit smoking improves long-term abstinence rates, especially among those with fewer depressive symptoms.