Neurogenetics of depression: a focus on reward processing and stress sensitivity

Effects of GABA, Sex, and Stress on Reward Learning in Current and Remitted Major Depression

BACKGROUND

Neurocognitive factors including aberrant reward learning, blunted GABA (gamma-aminobutyric acid), and potentiated stress sensitivity have been linked to anhedonia, a hallmark depressive symptom, possibly in a sex-dependent manner. However, previous research has not investigated the putative associations among these factors or the extent to which they represent trait- or state-based vulnerabilities for depression.

METHODS

Young adults with current major depressive disorder (MDD) (n = 44), remitted MDD (n = 42), and healthy control participants (HCs) (n = 44), stratified by sex assigned at birth, underwent magnetic resonance spectroscopy to assess macromolecular contaminated GABA (GABA+) and then a reward learning task before and after acute stress. We assessed changes in reward learning after stress and associations with GABA+.

RESULTS

Results revealed blunted baseline reward learning in participants with remitted MDD versus participants with current MDD and HCs but, surprisingly, no differences between participants with current MDD and HCs. Reward learning was reduced following acute stress regardless of depressive history. GABA+ in the rostral anterior cingulate cortex, but not the dorsolateral prefrontal cortex, was associated with reduced baseline reward learning only in female participants. GABA+ did not predict stress-related changes in reward learning.

CONCLUSIONS

To our knowledge, this is the first study to investigate associations among GABA, reward learning, and stress reactivity in current versus past depression. Hypothesized depression-related differences in reward learning did not emerge, precluding claims about state versus trait vulnerabilities. However, our finding that blunted GABA was associated with greater reward learning in female participants provides novel insights into sex-selective associations between the frontal GABAergic inhibitory system and reward processing.

Factors influencing stress and resilience among Egyptian medical students: a multi-centric cross-sectional study

BACKGROUND

Psychological stress is a common psychological comorbidity among medical students and worsens their quality of life. Psychological resilience is thought to have a protective role against stress. However, evidence regarding the prevalence of stress and resilience alongside their associated factors is scarce, especially in the Middle East. This is the first multicenter, cross-sectional study to investigate resilience and stress among Egyptian medical students.

METHODS

The current cross-sectional study was conducted on 2465 university students in seven public universities in Egypt. The universities were selected using the simple randomization method. The data was collected using a self-administered questionnaire consisting of four parts: demographic data, socioeconomic tool represented in the Family Affluence Scale (FAS), the Kessler Psychological Distress Scale (K10), and the Brief Resilience Scale (BRS). Data was analyzed in SPSS version 26 software.

RESULTS

The majority of the students were stressed (86.5%), most of whom had severe stress (48.9%). Most of the students had low resilience (49.9%), while only 3.2% had high resilience. In the logistic regression analysis, being a female, living alone, spending long hours on social media, and thinking of suicide or leaving medicine were associated with being stressed and having low resilience. Medical students with low resilience were significantly more liable to stress [Adjusted odds ratio (AOR) = 3.667, confidence interval (CI): 2.709-4.965, P = 0.000], and vice versa [AOR = 3.709, CI: 2.746-5.009, P = 0.000]. Interestingly, high socioeconomic status showed a significant association with high resilience (P = 0.004); nonetheless, it was not associated with stress (P = 0.993). Academic grades were not associated with both the level of stress and resilience. Aging, being in clinical or academic stages, smoking, having a chronic disease, and being financially-supported are neither associated with stress nor resilience.

CONCLUSIONS

The present study revealed that Egyptian medical students had low resilience and high stress, with a significant relationship between both of them. Further investigations via longitudinal study design to understand the resilience-stress relationship are recommended. Developing and implementing resilience-improving strategies in medical schools is highly recommended to decrease the prevalence of stress and its subsequent burdens.

Sex-Specific Vulnerability to Externalizing Problems: Sensitivity to Early Stress and Nucleus Accumbens Activation Over Adolescence

BACKGROUND

Exposure and sensitivity to early-life stress (ELS) are related to increased risk for psychopathology in adolescence. While cross-sectional studies have reported blunted nucleus accumbens (NAcc) activation in the context of these associations, researchers have not yet assessed the effects of ELS on developmental trajectories of activation. We examined whether trajectories are affected by stress and the moderating role of biological sex in predicting vulnerability to symptoms of psychopathology.

METHODS

Adolescents (n = 173) completed 3 assessments at 2-year intervals across puberty (ages 9-18 years). At baseline, we assessed objective ELS and stress sensitivity using the Traumatic Events Screening Inventory for Children. At all time points, we assessed NAcc activation using the Monetary Incentive Delay task and externalizing, internalizing, and total problems using the Youth Self-Report. We examined correlations between NAcc trajectories (extracted using linear mixed-effects models) with ELS and stress sensitivity and conducted multivariate regression analysis to examine the interaction of NAcc trajectories and biological sex in predicting symptoms of psychopathology.

RESULTS

Symptoms increased over adolescence. Stress sensitivity, but not objective ELS, was associated with decreasing trajectories of NAcc activation. Biological sex interacted with NAcc trajectories to predict psychopathology; boys, but not girls, with decreasing NAcc activation had more severe externalizing problems in adolescence. These findings were replicated in the putamen and caudate but not in the medial prefrontal cortex or control brain regions.

CONCLUSIONS

NAcc activation may be a sex-specific marker of externalizing problems in adolescence. Efforts to reduce stress sensitivity may help to decrease symptoms of psychopathology in adolescent boys.

Rethinking Research on Prediction and Prevention of Psychotherapy Dropout: A Mechanism-Oriented Approach

Dropout is a ubiquitous psychotherapy outcome in clinical practice and treatment research alike, yet it remains a poorly understood problem. Contemporary dropout research is dominated by models of prediction that lack a strong theoretical foundation, often drawing on data from clinical trials that report on dropout in an inconsistent and incomplete fashion. In this article, we assert that dropout is a critical treatment outcome that is worthy of investigation as a mechanistic process. After briefly describing the scope of the dropout problem, we discuss the many factors that limit the field's present understanding of dropout. We then articulate and illustrate a transdiagnostic conceptual framework for examining psychotherapy dropout in contemporary research, concluding with recommendations for future research. With a more comprehensive understanding of the factors affecting retention, research efforts can shift toward investigating key processes underlying treatment dropout, thus, boosting prediction and informing strategies to mitigate dropout in clinical practice.

Resilience to depression: Implication for psychological vaccination

From the vulnerability perspective, we often ask the question "why someone suffers from depression?" Despite outstanding achievements along this line, we still face high occurrence or recurrence and unsatisfied therapeutic efficacy of depression, suggesting that solely focusing on vulnerability perspective is insufficient to prevent and cure depression. Importantly, although experiencing same adversity, most people do not suffer from depression but manifest certain resilience, which could be used to prevent and cure depression, however, the systematic review is still lack. Here, we propose the concept "resilience to depression" to emphasize resilient diathesis against depression, by asking the question "why someone is exempted from depression?" Research evidence of resilience to depression has been reviewed systematically: positive cognitive style (clear purpose in life, hopefulness, et al.), positive emotion (emotional stability, et al.), adaptive behavior (extraversion, internal self-control, et al.), strong social interaction (gratitude and love, et al.), and neural foundation (dopamine circuit, et al.). Inspired by these evidence, "psychological vaccination" could be achieved by well-known real-world natural-stress vaccination (mild, controllable, and adaptive of stress, with help from parents or leaders) or newly developed "clinical vaccination" (positive activity intervention for current depression, preventive cognitive therapy for remitted depression, et al.), both of which aim to enhance the resilient psychological diathesis against depression, through events or training. Potential neural circuit vaccination was further discussed. This review calls for directing attention to resilient diathesis against depression, which offers a new thinking "psychological vaccination" in both prevention and therapy of depression.

Reinforcement-based responsiveness, depression, and anhedonia: A multi-method investigation of intergenerational risk

Offspring of depressed parents are at an increased risk for depression. Reward- and punishment-based systems might be mechanisms linking maternal outcomes to offspring depression and anhedonia. The current study was designed to investigate the intergenerational relations between maternal markers of reward and punishment responsiveness and their offspring's depression and anhedonia in a community sample of 40 mother (mean age = 44.5; SD = 6.82) and adolescent (mean age = 14.73; SD = 1.25; 52.5% female) dyads. Maternal markers of reward and punishment responsiveness were captured using self-report, behavioral, and neurophysiological methods, and self-reported depression and anhedonia symptoms were used as outcomes among the adolescent offspring. Maternal self-reported reward responsiveness and punishment learning rates were differentially associated with depression across male and female offspring. Regarding anhedonia, maternal punishment learning rate was positively related to adolescent anhedonia regardless of offspring biological sex. Maternal reward learning rate was also positively associated with anhedonia among male offspring. In general, low concurrence across self-report, behavioral, and neurophysiological markers of reward and punishment responsiveness was found. The results from the current study suggest that learning-rates on reinforcement-based behavioral tasks may be important objective markers to consider when evaluating intergenerational risk.

Reward sensitivity modulates the brain reward pathway in stress resilience via the inherent neuroendocrine system

In the previous 10 years, researchers have suggested a critical role for the brain reward system in stress resilience. However, no study has provided an empirical link between activity in the mesostriatal reward regions during stress and the recovery of cortisol stress response. Moreover, although reward sensitivity as a trait has been demonstrated to promote stress resilience, it remains unclear whether it modulates the brain reward system in stress resilience and how this effect is achieved by the inherent neuroendocrine system. To investigate these uncertainties, 70 young adults were recruited to participate in a ScanSTRESS task, and their brain imaging data and saliva samples (for cortisol assay) were collected during the task. In addition, we assessed reward sensitivity, cortisol awakening response, and intrinsic functional connectivity of the brain in all the participants. We found that left putamen activation during stress exposure positively predicted cortisol recovery. In addition, reward sensitivity was positively linked with activation of the left putamen, and this relationship was serially mediated by the cortisol awakening response and right hippocampus-left inferior frontal gyrus intrinsic connectivity. These findings suggest that reward sensitivity modulates reward pathways in stress resilience through the interplay of the diurnal stress response system and network of the hippocampus-prefrontal circuitry. Summarily, the current study built a model to highlight the dynamic and multifaceted interaction between pertinent allostatic factors in the reward-resilience pathway and uncovered new insight into the resilience function of the mesostriatal reward system during stress.

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Cortisol recovery can be predicted by activation of the left putamen in stress.

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Activation of the left putamen was positively linked with reward sensitivity.

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This relationship was serially mediated by the cortisol awakening response and right hippocampus-left inferior frontal gyrus intrinsic coupling.

Childhood trauma exposure and reward processing in healthy adults: A functional neuroimaging study

The association between childhood trauma exposure and risk of developing psychopathology may in part be mediated by the effects of chronic stress on dopaminergic neurotransmission. However, little is known about the differential effects of distinct trauma types on reward processing, particularly in adults without concurrent medical or psychiatric disorders. We examined the association of childhood trauma exposure, including the differential effects of abuse and neglect, with reward processing in healthy adults (n = 114). Functional magnetic resonance imaging during a monetary incentive delay task was used to assess neural activity in the ventral striatum and orbitofrontal cortex in relation to reward anticipation and reward outcome, respectively. Exposure to childhood trauma, including abuse and neglect, was assessed using the Childhood Trauma Questionnaire‐Short Form. We found a significant effect for abuse on ventral striatal activation during reward anticipation, adjusting for age, sex, scanner site, educational level, and household monthly income. There were no effects for abuse or neglect, independently or combined, on orbitofrontal cortex activation during reward outcome. Our findings suggest differential effects of childhood abuse on ventral striatum activation during reward anticipation in healthy adults.

Cortisol reactivity to stress predicts behavioral responsivity to reward moderation by sex, depression, and anhedonia

Depression is associated with blunted reactivity to acute stress, as well as blunted responsivity to rewards. However, the extent to which responses to stress are associated with responses to reward in individuals meeting criteria for a depressive disorder is unknown. The goal of this study was to examine the relation of responses to stress and reward, and to determine if this relation is moderated by depression diagnosis, anhedonia, and sex. Participants included 114 adults (68 depressed, 46 non-depressed; 75% women) recruited from the community. Stress reactivity was operationalized as the total salivary cortisol output to the Trier Social Stress Test (TSST; Kirschbaum et al., 1993). Response bias to monetary reward was assessed following the TSST recovery period with a probabilistic reward task (PRT; Pizzagalli et al., 2005). In men only, total cortisol output during the TSST was more strongly positively associated with response bias to reward across the three blocks of the PRT. In addition, among depressed participants with high levels of anhedonia, higher cortisol output during the TSST was significantly associated with higher overall response bias to reward. We suggest that in men, the stress and reward systems may both respond quickly, and resolve rapidly, in the face of acute stress. Further, in depression, our findings suggest that anhedonia may represent a specific phenotype in which the stress and reward systems are particularly tuned together.

[Anhedonia in depression: neurobiological and genetic aspects]

Anhedonia is indeed a pathogenetically important clinical phenotype and a promising endophenotype for depressive symptoms with a very high contribution of biological and genetic factors. Neurobiological mechanisms of anhedonia are impaired functioning of the reward system of the brain, which is confirmed by many neuroimaging, genetic and experimental studies. Anhedonia has a trans-diagnoctic character and should be understood as a complex phenomenon, and it is important to correctly evaluate it within the framework of a particular research paradigm. It seems optimal to form several complementary research strategies that evaluate the most important «facets» of anhedonia, regardless of the nosological form of the disease, within the framework of one study using various methods to search for adequate biomarkers of anhedonia severity (genetic, neuroimaging, biochemical). Given the high-quality organization of such comprehensive studies based on the correct methodology of evidence-based medicine, it is likely that significant biomarker systems will be available in the near future, which, if replicated in independent samples, can be used to personalize the diagnosis and treatment of depression.

The C Factor: Cognitive dysfunction as a transdiagnostic dimension in psychopathology

Research into cognitive functions across psychological disorders suggests that cognitive deficiencies may be present across multiple disorders, potentially pointing to a transdiagnostic phenomenon. More recently, a single dimension model of psychopathology, the p factor, has been proposed, in which cognitive deficits are thought to be an intrinsic construct, assumed to be transdiagnostic. However, no systematic investigation to date tested this hypothesis. The aim of the present study was to systematically review meta-analyses to assess the hypothesis that the C factor (cognitive dysfunction) is transdiagnostic in psychopathology and review potential moderators that may account for such a phenomenon. We conducted a systematic review of meta-analyses examining cognitive function across all disorders for which data were available. Included meta-analyses (n = 82), comprising 97 clinical samples, yielded 1,055 effect sizes. Twelve major disorders/categories (e.g., bipolar disorder, substance use disorders) were included, comprising 29 distinct clinical entities (e.g., euthymic bipolar disorder; alcohol use disorder). Results show that all disorders reviewed are associated with underperformance across cognitive domains, supporting the hypothesis that the C factor (or cognitive dysfunction) is a transdiagnostic factor related to p. To examine moderators that may explain or contribute to c, we first consider important interpretative limitations of neuropsychological data in psychopathology. More crucially, we review oft-neglected motivational and emotional transdiagnostic constructs of p, as prominent contributing constructs to the C factor. These constructs are offered as a roadmap for future research examining these constructs related to p, that contribute, and may account for cognitive dysfunctions in psychopathology.

Evaluation of the Effects of Developmental Trauma on Neurotransmitter Systems Using Functional Molecular Imaging

Early life stress (ELS) is strongly associated with psychiatric disorders such as anxiety, depression, and schizophrenia in adulthood. To date, biological, behavioral, and structural aspects of ELS have been studied extensively, but their functional effects remain unclear. Here, we examined NeuroPET studies of dopaminergic, glutamatergic, and serotonergic systems in ELS animal models. Maternal separation and restraint stress were used to generate single or complex developmental trauma. Body weights of animals exposed to single trauma were similar to those of control animals; however, animals exposed to complex trauma exhibited loss of body weight when compared to controls. In behavioral tests, the complex developmental trauma group exhibited a decrease in time spent in the open arm of the elevated plus-maze and an increase in immobility time in the forced swim test when compared to control animals. In NeuroPET studies, the complex trauma group displayed a reduction in brain uptake values when compared to single trauma and control groups. Of neurotransmitter systems analyzed, the rate of decrease in brain uptake was the highest in the serotonergic group. Collectively, our results indicate that developmental trauma events induce behavioral deficits, including anxiety- and depressive-like phenotypes and dysfunction in neurotransmitter systems.

Increased Reward-Related Activation in the Ventral Striatum During Stress Exposure Associated With Positive Affect in the Daily Life of Young Adults With a Family History of Depression. Preliminary Findings

Background: Being the offspring of a parent with major depression disorder (MDD) is a strong predictor for developing MDD. Blunted striatal responses to reward were identified in individuals with MDD and in asymptomatic individuals with family history of depression (FHD). Stress is a major etiological factor for MDD and was also reported to reduce the striatal responses to reward. The stress-reward interactions in FHD individuals has not been explored yet. Extending neuroimaging results into daily-life experience, self-reported ambulatory measures of positive affect (PA) were shown to be associated with striatal activation during reward processing. A reduction of self-reported PA in daily life is consistently reported in individuals with current MDD. Here, we aimed to test (1) whether increased family risk of depression is associated with blunted neural and self-reported reward responses. (2) the stress-reward interactions at the neural level. We expected a stronger reduction of reward-related striatal activation under stress in FHD individuals compared to HC. (3) the associations between fMRI and daily life self-reported data on reward and stress experiences, with a specific interest in the striatum as a crucial region for reward processing. Method: Participants were 16 asymptomatic young adults with FHD and 16 controls (HC). They performed the Fribourg Reward Task with and without stress induction, using event-related fMRI. We conducted whole-brain analyses comparing the two groups for the main effect of reward (rewarded > not-rewarded) during reward feedback in control (no-stress) and stress conditions. Beta weights extracted from significant activation in this contrast were correlated with self-reported PA and negative affect (NA) assessed over 1 week. Results: Under stress induction, the reward-related activation in the ventral striatum (VS) was higher in the FHD group than in the HC group. Unexpectedly, we did not find significant group differences in the self-reported daily life PA measures. During stress induction, VS reward-related activation correlated positively with PA in both groups and negatively with NA in the HC group. Conclusion: As expected, our results indicate that increased family risk of depression was associated with specific striatum reactivity to reward in a stress condition, and support previous findings that ventral striatal reward-related response is associated with PA. A new unexpected finding is the negative association between NA and reward-related ventral striatal activation in the HC group.

Reward-Processing Behavior in Depressed Participants Relative to Healthy Volunteers: A Systematic Review and Meta-analysis

IMPORTANCE

Dysfunctional reward processing is a leading candidate mechanism for the development of certain depressive symptoms, such as anhedonia. However, to our knowledge, there has not yet been a systematic assessment of whether and to what extent depression is associated with impairments on behavioral reward-processing tasks.

OBJECTIVE

To determine whether depression is associated with impairments in reward-processing behavior.

DATA SOURCES

The MEDLINE/PubMed, Embase, and PsycInfo databases were searched for studies that investigated reward processing using performance on behavioral tasks by individuals with depression and nondepressed control groups, published between January 1, 1946, and August 16, 2019.

STUDY SELECTION

Studies that contained data regarding performance by depressed and healthy control groups on reward-processing tasks were included in the systematic review and meta-analysis.

DATA EXTRACTION AND SYNTHESIS

Summary statistics comparing performance between depressed and healthy groups on reward-processing tasks were converted to standardized mean difference (SMD) scores, from which summary effect sizes for overall impairment in reward processing and 4 subcomponent categories were calculated. Study quality, heterogeneity, replicability-index, and publication bias were also assessed.

MAIN OUTCOME AND MEASURES

Performance on reward-processing tasks.

RESULTS

The final data set comprised 48 case-control studies (1387 healthy control individuals and 1767 individuals with major depressive disorder). The mean age was 37.85 years and 58% of the participants were women. These studies used tasks assessing option valuation (n = 9), reward bias (n = 6), reward response vigor (n = 12), reinforcement learning (n = 20), and grip force (n = 1). Across all tasks, depression was associated with small to medium impairments in reward-processing behavior (SMD = 0.345; 95% CI, 0.209-0.480). When examining reward-processing subcomponent categories, impairment was associated with tasks assessing option valuation (SMD = 0.309; 95% CI, 0.147-0.471), reward bias (SMD = 0.644; 95% CI, 0.270-1.017), and reinforcement learning (SMD = 0.352; 95% CI, 0.115-0.588) but not reward response vigor (SMD = 0.083; 95% CI, -0.144 to 0.309). The medication status of the major depressive disorder sample did not explain any of the variance in the overall effect size. There was significant between-study heterogeneity overall and in all subcomponent categories other than option valuation. Significant publication bias was identified overall and in the reinforcement learning category.

CONCLUSIONS AND RELEVANCE

Relative to healthy control individuals, individuals with depression exhibit reward-processing impairments, particularly for tests of reward bias, option valuation, and reinforcement learning. Understanding the neural mechanisms driving these associations may assist in designing novel interventions.

Colon-delivered short-chain fatty acids attenuate the cortisol response to psychosocial stress in healthy men: a randomized, placebo-controlled trial

Short-chain fatty acids (SCFAs) are products of microbial fermentation of dietary fiber in the colon and may mediate microbiota-gut-brain communication. However, their role in modulating psychobiological processes that underlie the development of stress- and anxiety-related disorders is not mechanistically studied in humans. In this triple-blind, randomized, placebo-controlled intervention trial, we examine in a parallel group design the effects of 1-week colonic SCFA-mixture delivery in doses equivalent to fermentation of 10 g or 20 g of arabinoxylan oligosaccharides on responses to psychosocial stress and fear tasks in 66 healthy men. We demonstrate that low and high doses of SCFAs significantly attenuate the cortisol response to psychosocial stress compared to placebo. Both doses of SCFAs increase serum SCFA levels and this increase in circulating SCFAs co-varies significantly with the attenuation of the cortisol response to psychosocial stress. Colonic SCFA delivery does not modulate fecal SCFA concentrations, serum brain-derived neurotrophic factor, cortisol awakening response, fear learning and extinction, or subjective mood ratings. These results demonstrate that colon-delivered SCFAs modulate hypothalamic-pituitary-adrenal axis reactivity to psychosocial stress, thereby supporting their hypothesized role in microbiota-gut-brain communication.

Common and specific dimensions of internalizing disorders are characterized by unique patterns of brain activity on a task of emotional cognitive control

Alterations in neural systems underlying cognitive control are well-documented across individuals with various internalizing disorders. The current study examined how individual differences in underlying traits related to internalizing disorders influence brain activation, as assessed by fMRI, when cognitive control must be exerted to make a decision about the emotional valence (positive, negative) of a task-relevant word displayed concurrently with a task-irrelevant emotional face. Taking a bi-factor model approach, fifty-five middle-aged female participants were characterized on symptom level on a common internalizing latent factor representing shared symptoms across anxiety and depression, as well as on specific factors remaining after taking the common internalizing factor into account: low positive affect, anxious arousal, and anxious apprehension. Contrasting activation on trials requiring higher vs. lower control revealed that higher levels of the Common Internalizing factor are associated with less deactivation of regions of the default mode network. Higher levels of the Low Positive Affect-specific factor are associated with less differentiation in engagement of portions of the fronto-parietal control network, while higher levels of the Anxious Arousal-specific factor are associated with less of a differentiation in activation of the thalamus. No effects were observed for level of the Anxious Apprehension-specific factor. These results suggest that prior findings of alterations in default mode activity associated with depression may not be specific to depressive symptoms per se but may characterize internalizing symptoms more generally. In addition, they suggest that reduced engagement of cognitive control regions may be more associated with low positive affect than depressive symptoms more generally.

Finding intestinal fortitude: Integrating the microbiome into a holistic view of depression mechanisms, treatment, and resilience

Depression affects at least 322 million people globally, or approximately 4.4% of the world's population. While the earnestness of researchers and clinicians to understand and treat depression is not waning, the number of individuals suffering from depression continues to increase over and above the rate of global population growth. There is a sincere need for a paradigm shift. Research in the past decade is beginning to take a more holistic approach to understanding depression etiology and treatment, integrating multiple body systems into whole-body conceptualizations of this mental health affliction. Evidence supports the hypothesis that the gut microbiome, or the collective trillions of microbes inhabiting the gastrointestinal tract, is an important factor determining both the risk of development of depression and persistence of depressive symptoms. This review discusses recent advances in both rodent and human research that explore bidirectional communication between the gut microbiome and the immune, endocrine, and central nervous systems implicated in the etiology and pathophysiology of depression. Through interactions with circulating inflammatory markers and hormones, afferent and efferent neural systems, and other, more niche, pathways, the gut microbiome can affect behavior to facilitate the development of depression, exacerbate current symptoms, or contribute to treatment and resilience. While the challenge of depression may be the direst mental health crisis of our age, new discoveries in the gut microbiome, when integrated into a holistic perspective, hold great promise for the future of positive mental health.

Early life stress and brain function: Activity and connectivity associated with processing emotion and reward

Investigating the developmental sequelae of early life stress has provided researchers the opportunity to examine adaptive responses to extreme environments. A large body of work has established mechanisms by which the stressful experiences of childhood poverty, maltreatment, and institutional care can impact the brain and the distributed stress systems of the body. These mechanisms are reviewed briefly to lay the foundation upon which the current neuroimaging literature has been built. More recently, developmental cognitive neuroscientists have identified a number of the effects of early adversity, including differential behavior and brain function. Among the most consistent of these findings are differences in the processing of emotion and reward-related information. The neural correlates of emotion processing, particularly frontolimbic functional connectivity, have been well studied in early life stress samples with results indicating accelerated maturation following early adversity. Reward processing has received less attention, but here the evidence suggests a deficit in reward sensitivity. It is as yet unknown whether the accelerated maturation of emotion-regulation circuits comes at the cost of delayed development in other systems, most notably the reward system. This review addresses the early life stress neuroimaging literature that has investigated emotion and reward processing, identifying important next steps in the study of brain function following adversity.

The Efficacy of Vortioxetine on Anhedonia in Patients With Major Depressive Disorder

Background: Anhedonia is a common, persistent, and disabling phenomenon in treated adults with Major Depressive Disorder (MDD). Hitherto, relatively few antidepressant agents have been evaluated with respect to their effect on anhedonia in MDD. Methods: This is a post-hoc analysis of a primary study that sought to evaluate the sensitivity to change of the THINC-integrated tool (THINC-it) in MDD (ClinicalTrials.gov Identifier: NCT03053362). Adults meeting DSM-5 criteria for MDD with at least moderate depressive symptom severity [i.e., Montgomery Åsberg Depression Rating Scale (MADRS) total score ≥20] were eligible. Subjects were recruited between October 2017 and August 2018 in Toronto, Ontario at the Brain and Cognition Discovery Foundation. All subjects received open-label vortioxetine (10-20 mg/day, flexibly-dosed) for 8 weeks. Herein, the primary outcome of interest was the change from baseline to endpoint in the Snaith-Hamilton Pleasure Scale (SHAPS) total score, as well as the MADRS anhedonia factor. The mediational effects of improvements in anhedonia on general function and quality of life, as measured by the Sheehan Disability Scale (SDS) and the 5-Item World Health Organization Well-Being Index (WHO-5), were secondarily assessed. Results: A total of 100 subjects with MDD were enrolled in the primary study and began treatment with vortioxetine. Vortioxetine significantly improved anhedonia as evidenced by significant baseline to endpoint improvements in SHAPS and MADRS anhedonia factor scores (p < 0.0001). Improvements in the SHAPS and the MADRS anhedonia factor correlated with improvements in general function (i.e., SDS) and quality of life (i.e., WHO-5) (p < 0.0001). Notably, improvements in anhedonia were found to mediate the association between improvements in overall depressive symptom severity (i.e., MADRS total score) and social functioning (i.e., social life component of the SDS) (p = 0.026). Conclusion: The unmet need in depression is to improve patient functioning and other patient-reported outcomes (e.g., quality of life). Antidepressant interventions capable of attenuating anhedonia as well as cognitive dysfunction in MDD may help in this regard, as improvement in these domains have been associated with improvement in psychosocial function and quality of life.

Genome-wide interaction study of a proxy for stress-sensitivity and its prediction of major depressive disorder

Individual response to stress is correlated with neuroticism and is an important predictor of both neuroticism and the onset of major depressive disorder (MDD). Identification of the genetics underpinning individual differences in response to negative events (stress-sensitivity) may improve our understanding of the molecular pathways involved, and its association with stress-related illnesses. We sought to generate a proxy for stress-sensitivity through modelling the interaction between SNP allele and MDD status on neuroticism score in order to identify genetic variants that contribute to the higher neuroticism seen in individuals with a lifetime diagnosis of depression compared to unaffected individuals. Meta-analysis of genome-wide interaction studies (GWIS) in UK Biobank (N = 23,092) and Generation Scotland: Scottish Family Health Study (N = 7,155) identified no genome-wide significance SNP interactions. However, gene-based tests identified a genome-wide significant gene, ZNF366, a negative regulator of glucocorticoid receptor function implicated in alcohol dependence (p = 1.48x10-7; Bonferroni-corrected significance threshold p < 2.79x10-6). Using summary statistics from the stress-sensitivity term of the GWIS, SNP heritability for stress-sensitivity was estimated at 5.0%. In models fitting polygenic risk scores of both MDD and neuroticism derived from independent GWAS, we show that polygenic risk scores derived from the UK Biobank stress-sensitivity GWIS significantly improved the prediction of MDD in Generation Scotland. This study may improve interpretation of larger genome-wide association studies of MDD and other stress-related illnesses, and the understanding of the etiological mechanisms underpinning stress-sensitivity.

Lipidomics in Major Depressive Disorder

Omic sciences coupled with novel computational approaches such as machine intelligence offer completely new approaches to major depressive disorder (MDD) research. The complexity of MDD's pathophysiology is being integrated into studies examining MDD's biology within the omic fields. Lipidomics, as a late-comer among other omic fields, is increasingly being recognized in psychiatric research because it has allowed the investigation of global lipid perturbations in patients suffering from MDD and indicated a crucial role of specific patterns of lipid alterations in the development and progression of MDD. Combinatorial lipid-markers with high classification power are being developed in order to assist MDD diagnosis, while rodent models of depression reveal lipidome changes and thereby unveil novel treatment targets for depression. In this systematic review, we provide an overview of current breakthroughs and future trends in the field of lipidomics in MDD research and thereby paving the way for precision medicine in MDD.

Housing Quality and Mental Health: the Association between Pest Infestation and Depressive Symptoms among Public Housing Residents

Housing quality, which includes structural and environmental risks, has been associated with multiple physical health outcomes including injury and asthma. Cockroach and mouse infestations can be prime manifestations of diminished housing quality. While the respiratory health effects of pest infestation are well documented, little is known about the association between infestation and mental health outcomes. To address this gap in knowledge and given the potential to intervene to reduce pest infestation, we assessed the association between household pest infestation and symptoms of depression among public housing residents. We conducted a cross-sectional study in 16 Boston Housing Authority (BHA) developments from 2012 to 2014 in Boston, Massachusetts. Household units were randomly selected and one adult (n = 461) from each unit was surveyed about depressive symptoms using the Center for Epidemiologic Study-Depression (CES-D) Scale, and about pest infestation and management practices. In addition, a home inspection for pests was performed. General linear models were used to model the association between pest infestation and high depressive symptoms. After adjusting for important covariates, individuals who lived in homes with current cockroach infestation had almost three times the odds of experiencing high depressive symptoms (adjusted OR = 2.9, 95% CI 1.9-4.4) than those without infestation. Dual infestation (cockroach and mouse) was associated with over five times the odds (adjusted odds = 5.1, 95% CI 3.0-8.5) of experiencing high depressive symptoms. Using a robust measure of cockroach and mouse infestation, and a validated depression screener, we identified associations between current infestation and depressive symptoms. Although the temporal directionality of this association remains uncertain, these findings suggest that the health impact of poor housing conditions extend beyond physical health to include mental health. The study adds important information to the growing body of evidence that housing contributes to population health and improvements in population health may not be possible without addressing deficiencies in the housing infrastructure.

Neurodevelopmental consequences of pediatric cancer and its treatment: applying an early adversity framework to understanding cognitive, behavioral, and emotional outcomes

Today, children are surviving pediatric cancer at unprecedented rates, making it one of modern medicine's true success stories. However, we are increasingly becoming aware of several deleterious effects of cancer and the subsequent "cure" that extend beyond physical sequelae. Indeed, survivors of childhood cancer commonly report cognitive, emotional, and psychological difficulties, including attentional difficulties, anxiety, and posttraumatic stress symptoms (PTSS). Cognitive late- and long-term effects have been largely attributed to neurotoxic effects of cancer treatments (e.g., chemotherapy, cranial irradiation, surgery) on brain development. The role of childhood adversity in pediatric cancer - namely, the presence of a life-threatening disease and endurance of invasive medical procedures - has been largely ignored in the existing neuroscientific literature, despite compelling research by our group and others showing that exposure to more commonly studied adverse childhood experiences (i.e., domestic and community violence, physical, sexual, and emotional abuse) strongly imprints on neural development. While these adverse childhood experiences are different in many ways from the experience of childhood cancer (e.g., context, nature, source), they do share a common element of exposure to threat (i.e., threat to life or physical integrity). Therefore, we argue that the double hit of early threat and cancer treatments likely alters neural development, and ultimately, cognitive, behavioral, and emotional outcomes. In this paper, we (1) review the existing neuroimaging research on child, adolescent, and adult survivors of childhood cancer, (2) summarize gaps in our current understanding, (3) propose a novel neurobiological framework that characterizes childhood cancer as a type of childhood adversity, particularly a form of early threat, focusing on development of the hippocampus and the salience and emotion network (SEN), and (4) outline future directions for research.

Polygenic Risk Scores in Clinical Psychology: Bridging Genomic Risk to Individual Differences

Genomewide association studies (GWASs) across psychiatric phenotypes have shown that common genetic variants generally confer risk with small effect sizes (odds ratio < 1.1) that additively contribute to polygenic risk. Summary statistics derived from large discovery GWASs can be used to generate polygenic risk scores (PRS) in independent, target data sets to examine correlates of polygenic disorder liability (e.g., does genetic liability to schizophrenia predict cognition?). The intuitive appeal and generalizability of PRS have led to their widespread use and new insights into mechanisms of polygenic liability. However, when currently applied across traits they account for small amounts of variance (<3%), are relatively uninformative for clinical treatment, and, in isolation, provide no insight into molecular mechanisms. Larger GWASs are needed to increase the precision of PRS, and novel approaches integrating various data sources (e.g., multitrait analysis of GWASs) may improve the utility of current PRS.

A Functional Polymorphism in the DRD1 Gene, That Modulates Its Regulation by miR-504, Is Associated with Depressive Symptoms

OBJECTIVE

The aim of this study was to examine a possible association between depressive symptoms and a functional polymorphism (rs686) that modulates the regulation of DRD1 gene by miR-504.

METHODS

A total of 239 young Colombian subjects were evaluated with the Patient Health Questionnaire-9 (PHQ-9) scale and genotyped for the rs686 polymorphism. A linear regression model, corrected by age and gender, was used.

RESULTS

A significant association between the rs686 polymorphism and PHQ-9 scores was found, under a dominant genetic model (p=0.0094).

CONCLUSION

These results provide novel evidence about the growing role of inherited variants in binding sites for brain-expressed miRNAs on depressive symptomatology.

Presentation and Neurobiology of Anhedonia in Mood Disorders: Commonalities and Distinctions

PURPOSE OF REVIEW

To focus on the clinical and behavioral presentation of anhedonia in mood disorders, as well as the differences and commonalities in the underlying neurocircuitry.

RECENT FINDINGS

Evidence suggests that depression is characterized by hypofunction of the reward system, while bipolar disorder manifests dysregulation of the behavioral activation system that increases goal-directed reward behavior. Importantly, strong evidence does not exist to suggest significant differences in anhedonia severity between depressed unipolar and bipolar patients, suggesting that there are more nuanced fluctuations in reward processing deficits in bipolar patients depending on their state. Both euthymic unipolar and bipolar patients frequently report residual reward dysfunction, which highlights the potential of reward processing deficits that give rise to the clinical symptom of anhedonia to be trait factors of mood disorders; however, the possibility that therapies are not adequately treating anhedonia could also explain the presence of residual symptoms. Reward processing represents a potential diagnostic and treatment marker for mood disorders. Further research should systematically explore the facets of reward processing in at-risk, affected, and remitted patients.

Perceived stress and poly-tobacco product use across adolescence: Patterns of association and gender differences

Perceived stress-an endophenotype indicative of the tendency to appraise stress as frequent, unpredictable and unmanageable-is associated with adolescent cigarette smoking. It is unclear whether this association: (1) extends to alternative tobacco products, like electronic cigarettes and hookah (tobacco water pipe), which are increasingly popular among youth, and (2) differs by gender. In this report, data were drawn from a population-based longitudinal cohort of youth in Southern California. Perceived stress was assessed at baseline (7th or 8th grade; 2010). Electronic cigarette, hookah, combustible cigarette, and cigar use were assessed at a 4-year follow-up (11th or 12th grade; 2014). After adjusting for confounders, polytomous logistic regressions showed that a standardized baseline perceived stress score (M = 0, SD = 1) predicted electronic cigarette, hookah, combustible cigarette, and cigar use and a poly-tobacco use index at the 4-year follow-up in the overall sample. Interactions between perceived stress and gender were also observed (Interaction Ps < 0.05), which demonstrated that the association of perceived stress with tobacco product use and poly-use were stronger in females (ORs for current use range: 1.47 to 1.72) than males (ORs range: 0.93 to 1.31). Adjusting for baseline perceived stress, the change in perceived stress from baseline to follow-up was also positively associated with use and poly-use of most tobacco products in females and in males to some extent. In the current era in which teen use of alternative tobacco products is increasingly common, adolescent tobacco use and poly-use research and prevention strategies should address gender-specific origins of tobacco product use risk and consider perceived stress and other emotional endophenotypes in such risk pathways.

Divergent anomaly in mesocorticolimbic dopaminergic circuits might be associated with different depressive behaviors, an animal study

BACKGROUND

The mesocorticolimbic dopamine system, which originates from the ventral tegmental area (VTA) and projects primarily to the prefrontal cortex (PFC), olfactory tubercle (OT), nucleus accumbens (NAc), dorsal striatum (ST), and the amygdala (AMy), plays a pivotal role in determining individual motivation and sensitivity to rewards, namely, anhedonia. Not all depressive individuals exhibited anhedonia, thus, it is natural to speculate that the heterogenous manifestations of depression might be related to the mesocorticolimbic dopamine system. Maternal deprivation (MD) and chronic unpredictable stress (CUPS) are two well-established depressogenic stressors, and they were proven to induce different depressive phenotypes.

METHODS

The depressive and anxiety-like behaviors of MD and CUPS-treated rats were measured by classical behavioral tests including open field, forced swimming, and sucrose preference test. The expression of D1-5 dopamine receptors and DAT mRNA and protein in the mesocorticolimbic dopamine system of rats exposed to MD and CUPS were measured by real-time PCR and Western blot, respectively.

RESULTS

Severe anhedonia was observed in MD but not CUPS rats. Divergent expression of D1 and D2 receptors and DAT mRNA and protein in the mesocorticolimbic dopamine system were found between MD and CUPS rats. Significant correlations between different depressive behaviors and D1-/D2-like receptors and DAT protein levels in the mesocorticolimbic dopamine system were observed.

CONCLUSION

Different depressive behaviors of rats such as anhedonia, passive coping behavior, and declined exploratory interest might be related to divergent dopaminergic pathways. Anhedonia is associated with the dysfunction of VTA-NAc and VTA-OT dopaminergic pathways, the passive coping behavior is related to the dysregulation of VTA-PFC and VTA-AMy pathways, and individual exploratory interest is associated with abnormal activity of VTA-PFC and VTA-ST pathways.

Imaging Genetics and Genomics in Psychiatry: A Critical Review of Progress and Potential

Imaging genetics and genomics research has begun to provide insight into the molecular and genetic architecture of neural phenotypes and the neural mechanisms through which genetic risk for psychopathology may emerge. As it approaches its third decade, imaging genetics is confronted by many challenges, including the proliferation of studies using small sample sizes and diverse designs, limited replication, problems with harmonization of neural phenotypes for meta-analysis, unclear mechanisms, and evidence that effect sizes may be more modest than originally posited, with increasing evidence of polygenicity. These concerns have encouraged the field to grow in many new directions, including the development of consortia and large-scale data collection projects and the use of novel methods (e.g., polygenic approaches, machine learning) that enhance the quality of imaging genetic studies but also introduce new challenges. We critically review progress in imaging genetics and offer suggestions and highlight potential pitfalls of novel approaches. Ultimately, the strength of imaging genetics and genomics lies in their translational and integrative potential with other research approaches (e.g., nonhuman animal models, psychiatric genetics, pharmacologic challenge) to elucidate brain-based pathways that give rise to the vast individual differences in behavior as well as risk for psychopathology.

Genesis and Maintenance of Attentional Biases: The Role of the Locus Coeruleus-Noradrenaline System

Emotionally arousing events are typically better remembered than mundane ones, in part because emotionally relevant aspects of our environment are prioritized in attention. Such biased attentional tuning is itself the result of associative processes through which we learn affective and motivational relevance of cues. We propose that the locus coeruleus-noradrenaline (LC-NA) system plays an important role in the genesis of attentional biases through associative learning processes as well as their maintenance. We further propose that individual differences in and disruptions of the LC-NA system underlie the development of maladaptive biases linked to psychopathology. We provide support for the proposed role of the LC-NA system by first reviewing work on attentional biases in development and its link to psychopathology in relation to alterations and individual differences in NA availability. We focus on pharmacological manipulations to demonstrate the effect of a disrupted system as well as the ADRA2b polymorphism as a tool to investigate naturally occurring differences in NA availability. We next review associative learning processes that-modulated by the LC-NA system-result in such implicit attentional biases. Further, we demonstrate how NA may influence aversive and appetitive conditioning linked to anxiety disorders as well as addiction and depression.

Reduced Hedonic Capacity/Approach Motivation Relates to Blunted Responsivity to Gain and Loss Feedback in Children

Adolescents and adults with major depressive disorder or elevated depressive symptoms show reduced reward responses and tend to show enhanced responses to negative stimuli. However, reward-related behaviors and adaptive responses to negative feedback undergo dramatic changes across puberty. Thus, key questions remain regarding how altered incentive processing relates to depressive and anhedonic symptoms in prepubertal child populations. Twenty-four nonclinical prepubertal children 7-10 years of age (15 male; 16 Caucasian) completed two signal detection tasks that assessed behavioral responsivity to candy gain and loss feedback, respectively. These tasks were based on Pizzagalli's probabilistic reward task where asymmetric feedback leads to greater bias toward the more frequently rewarded response in more hedonic or nondepressed adults. We further modified the task to create a version where incorrect responses could result in losses from an original allotment of candy. Children and parents/guardians also completed individual difference questionnaires to assess the child's depressive symptoms, general affect, and hedonic capacity/approach motivation. Regressions indicated a relation between hedonic capacity/approach motivation (child self-report) and response bias in both gain and loss tasks. No significant relations were observed between depressive (child self-report), internalizing (parent report), or externalizing symptoms (parent report) and bias in either the gain or loss task in this small sample. These results suggest that reduced hedonic capacity/approach motivation is associated with blunted responses to both gain and loss feedback in prepubertal children.

Reduced Ventral Tegmental Area-Hippocampal Connectivity in Children and Adolescents Exposed to Early Threat

BACKGROUND

Preclinical data suggest that early life stress has detrimental effects on the brain's dopaminergic system, particularly the mesocorticolimbic pathway. Altered dopamine function is thought to contribute to the development of stress-related pathologies; yet, little is known about the impact of early stress on dopamine systems during childhood and adolescence, when stress-related disorders frequently emerge. Here, we evaluate the impact of early threat exposure (violence, abuse) on functional connectivity of putative dopaminergic midbrain regions, the ventral tegmental area (VTA) and substantia nigra (SN), giving rise to mesocorticolimbic and nigrostriatal pathways, respectively.

METHODS

Resting-state functional magnetic resonance imaging scans were completed in 43 trauma-exposed and 43 matched comparison youth (ages 7-17). Functional connectivity of the VTA and SN were compared between groups.

RESULTS

The trauma group demonstrated lower functional connectivity between the VTA and hippocampus. No group differences in SN connectivity were observed. Across all participants, there were age-related decreases in connectivity of both VTA and SN with the hippocampus, suggesting that age-related attenuations in VTA-hippocampal circuitry may be exacerbated in trauma-exposed youth. Higher levels of anxiety symptomology were associated with reduced SN-nucleus accumbens connectivity.

CONCLUSIONS

Prior research suggests that VTA-hippocampal circuitry is critical for the gating of new information into long-term memory. Lower connectivity in this circuitry suggests a novel mechanism that may serve to adaptively prevent the overwriting of a previously stored trauma memory, but at the same time contribute to the broad range of cognitive and emotional difficulties linked to early stress exposure.

Toward understanding the impact of trauma on the early developing human brain

Traumatic experiences early in life predispose animals and humans to later cognitive-behavioral, emotional, and somatic problems. In humans, traumatic experiences are strong predictors of psychiatric illness. A growing body of research has emphasized alterations in neurological structure and function that underscore phenotypic changes following trauma. However, results are mixed and imprecise. We argue that future translation of neurological findings to clinical practice will require: (1) discovery of neurobehavioral associations within a longitudinal context, (2) dissociation of trauma types and of trauma versus chronic stress, and (3) better localization of neural sequelae considerate of the fine resolution of neural circuitry. We provide a brief overview of early brain development and highlight the role of longitudinal research in unearthing brain-behavior relations in youth. We relay an emergent framework in which dissociable trauma types are hypothesized to impact distinct, rationally informed neural systems. In line with this, we discuss the long-standing challenge of separating effects of chronic stress and trauma, as these are often intertwined. We bring to light inconsistencies in localization of neural correlates of trauma, emphasizing results in medial prefrontal regions. We assert that more precise spatial brain localization will help to advance prevailing models of trauma pathways and inform future research.

COMT Val(158) Met genotype is associated with reward learning: a replication study and meta-analysis

Identifying mechanisms through which individual differences in reward learning emerge offers an opportunity to understand both a fundamental form of adaptive responding as well as etiological pathways through which aberrant reward learning may contribute to maladaptive behaviors and psychopathology. One candidate mechanism through which individual differences in reward learning may emerge is variability in dopaminergic reinforcement signaling. A common functional polymorphism within the catechol-O-methyl transferase gene (COMT; rs4680, Val(158) Met) has been linked to reward learning, where homozygosity for the Met allele (linked to heightened prefrontal dopamine function and decreased dopamine synthesis in the midbrain) has been associated with relatively increased reward learning. Here, we used a probabilistic reward learning task to asses response bias, a behavioral form of reward learning, across three separate samples that were combined for analyses (age: 21.80 ± 3.95; n = 392; 268 female; European-American: n = 208). We replicate prior reports that COMT rs4680 Met allele homozygosity is associated with increased reward learning in European-American participants (β = 0.20, t = 2.75, P < 0.01; ΔR(2) = 0.04). Moreover, a meta-analysis of 4 studies, including the current one, confirmed the association between COMT rs4680 genotype and reward learning (95% CI -0.11 to -0.03; z = 3.2; P < 0.01). These results suggest that variability in dopamine signaling associated with COMT rs4680 influences individual differences in reward which may potentially contribute to psychopathology characterized by reward dysfunction.

Acupuncture treatment modulates the corticostriatal reward circuitry in major depressive disorder

Major depressive disorder (MDD) is a common disorder with a high prevalence and significant social and economic impacts. Nevertheless, the treatment of MDD is far from satisfactory. Acupuncture treatment has emerged as a promising method for treating MDD. However, the neural mechanism by which acupuncture reduces depressive symptoms is not fully understood. Studies have shown that the corticostriatal reward circuitry is associated with the pathophysiology of MDD; thus, we investigated the corticostriatal resting-state functional connectivity (rsFC) before and after real and sham acupuncture treatments combined with the antidepressant fluoxetine. Forty-six female major depressive patients were assigned to either verum acupuncture plus fluoxetine (n = 22) or sham acupuncture plus fluoxetine (n = 24) treatment for 8 weeks, and resting state functional magnetic resonance imaging (fMRI) data were collected before the first and after the last treatment sessions. The results showed that compared with sham acupuncture, the verum acupuncture group showed: (1) significantly increased rsFC between inferior ventral striatum and medial prefrontal cortex, ventral rostral putamen and amygdala/parahippocampus, as well as dorsal caudate and middle temporal gyrus; (2) significantly decreased rsFC between right ventral rostral putamen and right dorsolateral prefrontal cortex, and right dorsal caudate and bilateral cerebellar tonsil. The increased rsFC between the inferior ventral striatum and medial prefrontal cortex, ventral rostral putamen and amygdala/parahippocampus were significantly positively associated with decreased clinical scores (Montgomery-Åsberg Depression Rating Scale and Self-Rating Depression Scale scores) at the end of the eight-week treatment. Our findings suggest that acupuncture may achieve treatment effects by modulating the corticostriatal reward/motivation circuitry in MDD patients.

Investigating the Impact of a Genome-Wide Supported Bipolar Risk Variant of MAD1L1 on the Human Reward System

Recent genome-wide association studies have identified MAD1L1 (mitotic arrest deficient-like 1) as a susceptibility gene for bipolar disorder and schizophrenia. The minor allele of the single-nucleotide polymorphism (SNP) rs11764590 in MAD1L1 was associated with bipolar disorder. Both diseases, bipolar disorder and schizophrenia, are linked to functional alterations in the reward system. We aimed at investigating possible effects of the MAD1L1 rs11764590 risk allele on reward systems functioning in healthy adults. A large homogenous sample of 224 young (aged 18-31 years) participants was genotyped and underwent functional magnetic resonance imaging (fMRI). All participants performed the 'Desire-Reason Dilemma' paradigm investigating the neural correlates that underlie reward processing and active reward dismissal in favor of a long-term goal. We found significant hypoactivations of the ventral tegmental area (VTA), the bilateral striatum and bilateral frontal and parietal cortices in response to conditioned reward stimuli in the risk allele carriers compared with major allele carriers. In the dilemma situation, functional connectivity between prefrontal brain regions and the ventral striatum was significantly diminished in the risk allele carriers. Healthy risk allele carriers showed a significant deficit of their bottom-up response to conditioned reward stimuli in the bilateral VTA and striatum. Furthermore, functional connectivity between the ventral striatum and prefrontal areas exerting top-down control on the mesolimbic reward system was reduced in this group. Similar alterations in reward processing and disturbances of prefrontal control mechanisms on mesolimbic brain circuits have also been reported in bipolar disorder and schizophrenia. Together, these findings suggest the existence of an intermediate phenotype associated with MAD1L1.

Prevalencia de depresión y factores asociados en hombres

El objetivo del presente estudio fue evaluar la prevalencia de depresión, detectar el riesgo suicida e identificar los factores sociodemográficos y personales asociados a este trastorno. La muestra no aleatorizada estuvo conformada por 1525 hombres colombianos con edades entre 18 y 83 años procedentes de 22 departamentos y de distintos niveles educativos. Para evaluar la depresión se usó el Cuestionario de Depresión para Hombres (Álvarez y Londoño, 2012); para evaluar la comorbilidad con ansiedad se usó la Escala de Ansiedad HADS (Zigmond y Snaith, 1983) y el IMAFE (Lara, 1991); y para recolectar información acerca de los factores personales y sociodemográficos se usó una ficha de registro. Se analizaron los datos para calcular la prevalencia de corte, el riesgo suicida, la comorbilidad a través del uso del paquete estadístico SPSS. Se concluye que la prevalencia real reportada y el riesgo suicida en la población estudiada son más altos que los detectados usando un instrumento no sensible al género.

Future Research Directions in the Positive Valence Systems: Measurement, Development, and Implications for Youth Unipolar Depression

The Positive Valence Systems (PVS) have been introduced by the National Institute of Mental Health as a domain to help organize multiple constructs focusing on reward-seeking behaviors. However, the initial working model for this domain is strongly influenced by adult constructs and measures. Thus, the present review focuses on extending the PVS into a developmental context. Specifically, the review provides some hypotheses about the structure of the PVS, how PVS components may change throughout development, how family history of depression may influence PVS development, and potential means of intervening on PVS function to reduce onsets of depression. Future research needs in each of these areas are highlighted.

Reward Processing and Risk for Depression Across Development

Striatal response to reward has been of great interest in the typical development and psychopathology literatures. These parallel lines of inquiry demonstrate that although typically developing adolescents show robust striatal response to reward, adolescents with major depressive disorder (MDD) and those at high risk for MDD show a blunted response to reward. Understanding how these findings intersect is crucial for the development and application of early preventative interventions in at-risk children, ideally before the sharp increase in the rate of MDD onset that occurs in adolescence. Robust findings relating blunted striatal response to reward and MDD risk are reviewed and situated within a normative developmental context. We highlight the need for future studies investigating longitudinal development, specificity to MDD, and roles of potential moderators and mediators.

Enhanced default mode network connectivity with ventral striatum in subthreshold depression individuals

Subthreshold depression (StD) is a highly prevalent condition associated with increased service utilization and social morbidity. Nevertheless, due to limitations in current diagnostic systems that set the boundary for major depressive disorder (MDD), very few brain imaging studies on the neurobiology of StD have been carried out, and its underlying neurobiological mechanism remains unclear. In recent years, accumulating evidence suggests that the disruption of the default mode network (DMN), a network involved in self-referential processing, affective cognition, and emotion regulation, is involved in major depressive disorder. Using independent component analysis, we investigated resting-state default mode network (DMN) functional connectivity (FC) changes in two cohorts of StD patients with different age ranges (young and middle-aged, n = 57) as well as matched controls (n = 79). We found significant FC increase between the DMN and ventral striatum (key region in the reward network), in both cohorts of StD patients in comparison with controls. In addition, we also found the FC between the DMN and ventral striatum was positively and significantly associated with scores on the Center for Epidemiologic Studies Depression Scale (CES-D), a measurement of depressive symptomatology. We speculate that this enhanced FC between the DMN and the ventral striatum may reflect a self-compensation to ameliorate the lowered reward function.

Behavioral and self-reported sensitivity to reward are linked to stress-related differences in positive affect

Despite the high prevalence of stress exposure healthy adaptation or resilience is a common response. Theoretical work and recent empirical evidence suggest that a robust reward system, in part, supports healthy adaptation by preserving positive emotions even under exceptionally stressful circumstances. We tested this prediction by examining empirical relations among behavioral and self-reported measures of sensitivity to reward, trait resilience, and measures of affect in the context of experimentally induced stress. Using a quasi-experimental design we obtained measures of sensitivity to reward (self-report and behavioral), as well as affective and physiological responses to experimental psychosocial stress in a sample of 140 healthy college-age participants. We used regression-based moderation and mediational models to assess associations among sensitivity to reward, affect in the context of stress, and trait resilience and found that an interaction between exposure to experimental stress and self-reported sensitivity to reward predicted positive affect following experimental procedure. Participants with high sensitivity to reward reported higher positive affect following stress. Moreover, positive affect during or after stress mediated the relation between sensitivity to reward and trait resilience. Consistent with the prediction that a robust reward system serves as a protective factor against stress-related negative outcomes, our results found predictive associations among sensitivity to reward, positive affect, and resilience.

Anhedonia is associated with blunted reward sensitivity in first-degree relatives of patients with major depression

BACKGROUND

Anhedonia is a cardinal feature of major depression and is hypothesized to be driven by low motivation, in particular blunted reward sensitivity. It has been suggested to be a marker that represents a genetic predisposition to this disorder. However, little is known about the mechanisms underlying this heightened risk in unaffected first-degree relatives of patients with major depression. We previously demonstrated abnormal reward biases in acutely depressed patients. The present study aimed to examine the development of reward bias in first-degree relatives of patients with major depression.

METHODS

Forty-seven first-degree relatives of patients with major depression (26 females, age 18-52) and 60 healthy controls with no family history of depression (34 females, age 21-48) were recruited. A probabilistically rewarded difficult visual discrimination task, in which participants were instructed about the contingencies, was used to assess blunted reward sensitivity. A response bias towards the more frequently rewarded stimulus (termed "reward bias") was the primary outcome variable in this study. Participants also completed self-reported measures of anhedonia and depressive symptoms.

RESULTS

Compared with the control group, relatives of patients with major depression with sub-clinical depressive symptoms displayed a blunted reward bias. Relatives without symptoms displayed largely intact motivational processing on both self-report and experimental measures. The degree of anhedonia was associated with attenuated reward bias in first-degree relatives of patients with major depression, especially in those with sub-clinical symptoms.

LIMITATIONS

The study did not include a depressed patient group, which restricted our ability to interpret the observed group differences.

CONCLUSIONS

Blunted reward sensitivity may be largely manifested in a subgroup of relatives with high levels of depressive symptoms.

Genetic Moderation of Stress Effects on Corticolimbic Circuitry

Stress exposure is associated with individual differences in corticolimbic structure and function that often mirror patterns observed in psychopathology. Gene x environment interaction research suggests that genetic variation moderates the impact of stress on risk for psychopathology. On the basis of these findings, imaging genetics, which attempts to link variability in DNA sequence and structure to neural phenotypes, has begun to incorporate measures of the environment. This research paradigm, known as imaging gene x environment interaction (iGxE), is beginning to contribute to our understanding of the neural mechanisms through which genetic variation and stress increase psychopathology risk. Although awaiting replication, evidence suggests that genetic variation within the canonical neuroendocrine stress hormone system, the hypothalamic-pituitary-adrenal axis, contributes to variability in stress-related corticolimbic structure and function, which, in turn, confers risk for psychopathology. For iGxE research to reach its full potential it will have to address many challenges, of which we discuss: (i) small effects, (ii) measuring the environment and neural phenotypes, (iii) the absence of detailed mechanisms, and (iv) incorporating development. By actively addressing these challenges, iGxE research is poised to help identify the neural mechanisms underlying genetic and environmental associations with psychopathology.

Early-life adversity and adolescent depression: mechanisms involving the ventral striatum

Early-life adversity is a well-established risk factor for the development of depression later in life. Here we discuss the relationship between early-life adversity and depression, focusing specifically on effects of early-life caregiver deprivation on alterations in the neural and behavioral substrates of reward-processing. We also examine vulnerability to depression within the context of sensitive periods of neural development and the timing of adverse exposure. We further review the development of the ventral striatum, a limbic structure implicated in reward processing, and its role in depressive outcomes following early-life adversity. Finally, we suggest a potential neurobiological mechanism linking early-life adversity and altered ventral striatal development. Together these findings may help provide further insight into the role of reward circuitry dysfunction in psychopathological outcomes in both clinical and developmental populations.

Blunted neural response to rewards as a vulnerability factor for depression: Results from a family study

Depressive disorders are associated with significant economic and public health burdens as well as increased morbidity. Yet, perhaps due to the heterogeneous nature of the disease, prevention and intervention efforts are only moderately efficacious. A better understanding of core mechanisms of depressive disorders might aid in the development of more targeted intervention, and perhaps help identify individuals at risk. One mechanism that may be particularly important to depressive phenotypes is reward insensitivity. Examination of neurobiological correlates of reward-processing, which should relate more directly to the neuropathology of depression, may be helpful in identifying liability for the disorder. To that end, we used a family study design to examine whether a neural response to rewards is a familial risk factor for depression in a sample of probands with a wide range of internalizing psychopathology, as well as their biological siblings. Event-related potentials were recorded during a simple forced-choice gambling paradigm, in which participants could either win or lose small amounts of money. Lower levels of positive affect in probands predicted a reduced neural response to rewards in siblings, even over and above the sibling's own level of positive and negative affect. Additionally, the neural response to rewards was familial (i.e., correlated among siblings). Combined, these analyses suggest that a blunted neural response to rewards may be useful in identifying individuals vulnerable to depressive illnesses.

Replication study implicates COMT val158met polymorphism as a modulator of probabilistic reward learning

Previous studies suggest that a single nucleotide polymorphism in the catechol-O-methyltransferase (COMT) gene (val158met) may modulate reward-guided decision making in healthy individuals. The polymorphism affects dopamine catabolism and thus modulates prefrontal dopamine levels, which may lead to variation in individual responses to risk and reward. We previously showed, using tasks that index reward responsiveness (measured by responses bias towards reinforced stimuli) and risk taking (measured by the Balloon Analogue Risk Task), that COMT met homozygotes had increased reward responsiveness and, thus, an increased propensity to seek reward. In this study, we sought to replicate these effects in a larger, independent cohort of Caucasian UK university students and staff with similar demographic characteristics (n = 101; 54 females, mean age: 22.2 years). Similarly to our previous study, we observed a significant trial × COMT genotype interaction (P = 0.047; η(2) = 0.052), which was driven by a significant effect of COMT on the incremental acquisition of response bias [response bias at block 3 - block 1 (met/met > val/val: P = 0.028) and block 3 - block 2 (met/met > val/val: P = 0.007)], suggesting that COMT met homozygotes demonstrated higher levels of reward responsiveness by the end of the task. However, we failed to see main effects of COMT genotype on overall response bias or risk-seeking behaviour. These results provide additional evidence that prefrontal dopaminergic variation may have a role in reward responsiveness, but not risk-seeking behaviour. Our findings may have implications for neuropsychiatric disorders characterized by clinical deficits in reward processing such as anhedonia.