Iowa Gambling Task performance in euthymic bipolar I disorder: a meta-analysis and empirical study

The Types of Psychosocial Factors Associated with Suicidality Outcomes for People Living with Bipolar Disorder: A Scoping Review

Bipolar Disorder is associated with high rates of suicidal thoughts, behaviors, and outcomes, yet the lived experience of suicidality and Bipolar Disorder is not particularly well understood. Understanding the role of psychosocial aetiologies in suicidality outcomes for those living with Bipolar Disorder is key for developing appropriately targeted interventions focusing on factors that are amenable to change. In line with PRISMA guidance, we conducted a scoping review to identify the types of psychosocial factors studied in relation to the experience of suicidality for people living with Bipolar Disorder diagnoses. Systematic literature searches identified a sample of 166 articles from which key study data were extracted and charted. A narrative synthesis of the reviewed literature is presented ordered by the factors investigated across studies, a frequency count of the types of psychological/social aetiologies studied, and a brief overview of the key findings for each aetiology. Most of the identified literature took the form of quantitative cross-sectional studies, with only one qualitative study and 18 quantitative prospective studies. The most studied aetiologies were trauma (specifically early adverse experiences and childhood traumas) and stressful life events, impulsivity (primarily subjective self-reported trait impulsivity), social support and functioning, and personality/temperament factors. Only six studies in the final sample reported basing their research questions and/or hypotheses on an explicit theoretical model of suicide. The literature was primarily focused on using self-report measurements of key aetiologies and on factors which lead to worsened suicidality rather than focusing on potentially protective or buffering factors. Future research needs to better justify the aetiologies investigated in relation to suicidality outcomes for people living with Bipolar Disorder, including a firmer basis in theory and hypothesis testing, more prospective designs, and the use of alternative assessments of psychosocial aetiologies in addition to self-report questionnaires.

Polygenic contributions to performance on the Balloon Analogue Risk Task

Risky decision-making is a common, heritable endophenotype seen across many psychiatric disorders. Its underlying genetic architecture is incompletely explored. We examined behavior in the Balloon Analogue Risk Task (BART), which tests risky decision-making, in two independent samples of European ancestry. One sample (n = 1138) comprised healthy participants and some psychiatric patients (53 schizophrenia, 42 bipolar disorder, 47 ADHD); the other (n = 911) excluded for recent treatment of various psychiatric disorders but not ADHD. Participants provided DNA and performed the BART, indexed by mean adjusted pumps. We constructed a polygenic risk score (PRS) for discovery in each dataset and tested it in the other as replication. Subsequently, a genome-wide MEGA-analysis, combining both samples, tested genetic correlation with risk-taking self-report in the UK Biobank sample and psychiatric phenotypes characterized by risk-taking (ADHD, Bipolar Disorder, Alcohol Use Disorder, prior cannabis use) in the Psychiatric Genomics Consortium. The PRS for BART performance in one dataset predicted task performance in the replication sample (r = 0.13, p = 0.000012, pFDR = 0.000052), as did the reciprocal analysis (r = 0.09, p = 0.0083, pFDR=0.04). Excluding participants with psychiatric diagnoses produced similar results. The MEGA-GWAS identified a single SNP (rs12023073; p = 3.24 × 10-8) near IGSF21, a protein involved in inhibitory brain synapses; replication samples are needed to validate this result. A PRS for self-reported cannabis use (p = 0.00047, pFDR = 0.0053), but not self-reported risk-taking or psychiatric disorder status, predicted behavior on the BART in our MEGA-GWAS sample. The findings reveal polygenic architecture of risky decision-making as measured by the BART and highlight its overlap with cannabis use.

Shuffle the Decks: Children Are Sensitive to Incidental Nonrandom Structure in a Sequential-Choice Task

As children age, they can learn increasingly complex features of environmental structure-a key prerequisite for adaptive decision-making. Yet when we tested children (N = 304, 4-13 years old) in the Children's Gambling Task, an age-appropriate variant of the Iowa Gambling Task, we found that age was negatively associated with performance. However, this paradoxical effect of age was found only in children who exhibited a maladaptive deplete-replenish bias, a tendency to shift choices after positive outcomes and repeat choices after negative outcomes. We found that this bias results from sensitivity to incidental nonrandom structure in the canonical, deterministic forms of these tasks-and that it would actually lead to optimal outcomes if the tasks were not deterministic. Our results illustrate that changes in decision-making across early childhood reflect, in part, increasing sensitivity to environmental structure.

No group differences in Traditional Economics Measures of loss aversion and framing effects in bipolar I disorder

Bipolar disorder (BD) is associated with impaired decision making, yet few studies have adopted paradigms from behavioral economics to decompose which, if any, aspects of decision making may be impacted. This may be particularly relevant for decision-making processes relevant to known difficulties with emotive dysfunction and corresponding reward dysregulation in BD. Participants with bipolar I disorder (BD; n = 44) and non-psychiatric healthy controls (CTL; n = 28) completed three well-validated behavioral economics decision making tasks via a remote-based survey, including loss aversion and framing effects, that examined sensitivity to probabilities and potential gains and losses in monetary and non-monetary domains. Consistent with past work, we found evidence of moderate loss aversion and framing effects across all participants. No group differences were found in any of the measures of loss aversion or framing effects. We report no group differences between bipolar and non-psychiatric groups with respect to loss aversion and framing effects using a remote-based survey approach. These results provide a framework future studies to explore similar tasks in clinical populations and suggest the context and degree to which decision making is altered in BD may be rooted in a more complex cognitive mechanism that warrants future research.

Decision making and its associations to neurocognitive functions, psychopathology, and the home environment in seven-year-old children at familial high risk of schizophrenia or bipolar disorder: The Danish High Risk and Resilience Study VIA 7

BACKGROUND

Slower and suboptimal decision making has been identified in adults with schizophrenia and bipolar disorder. Owing to the limited evidence on decision making in first-degree relatives, we aimed to investigate, whether alterations in decision making are present in young children at familial high risk of bipolar disorder or schizophrenia.

METHODS

In this population-based cohort study we assessed decision making in 197 children at familial high risk of schizophrenia (FHR-SZ), 115 children at familial high risk of bipolar disorder (FHR-BP), and 190 controls aged seven using the Cambridge Gambling Task. Potential associations to neurocognition, psychopathology, and the home environment were investigated.

RESULTS

Children at FHR-SZ or FHR-BP displayed intact decision making. Quality of decision making showed significant but weak cross-sectional associations to neurocognition and adequacy of the home environment. Associations to aspects of executive functions and the home environment differed across groups.

LIMITATIONS

Due to the cross-sectional nature of this study, the predictive value of efficient and inefficient decision making remains to be investigated in planned follow-up studies of this cohort.

CONCLUSIONS

Young children at FHR-SZ or FHR-BP do not differ from controls in decision making efficacy, which does not appear to be an early risk marker of bipolar disorder or schizophrenia. Decision making is weakly associated to neurocognition and the home environment, but not to general intelligence or psychopathology.

Impulsivity, decision-making and risk-taking behaviour in bipolar disorder: a systematic review and meta-analysis

Despite the robust body of work on cognitive aspects of bipolar disorder (BD), a clear profile of associated impairments in impulsivity, decision-making and risk-taking from studies that use behavioural measures has yet to be established. A systematic review, across four electronic databases (PsycINFO, MEDLINE/PubMed, ScienceDirect and Scopus), of literature published between January 1999 and December 2018 was carried out in accordance with the PRISMA statement. The protocol was registered on PROSPERO (CRD42018114684). A fixed-effect and random-effects meta-analysis using the Hedges' g (ES) estimate was performed. The analysis revealed significant impairment in BD individuals with medium effect sizes in various aspects of impulsivity - response inhibition (ES = 0.49; p < 0.0001), delay of gratification (ES = 0.54; p < 0.0001) and inattention (ES = 0.49; p < 0.0001) - and in decision-making (ES = 0.61, p = 0.0002), but no significant impairment in risk-taking behaviour (ES = 0.41; p = 0.0598). Furthermore, we found significant heterogeneity between studies for decision-making and risk-taking behaviour but not for impulsivity. Impaired risk-taking behaviour was significant in a subgroup of BD-I and euthymic individuals (ES = 0.92; p < 0.0001) with no significant heterogeneity. A stratification analysis revealed comparable results in euthymic and non-euthymic individuals for impulsivity. Our findings suggest that behaviour impulsivity is elevated in all phases of BD, representing a core and clinically relevant feature that persists beyond mood symptoms. More studies about decision-making and risk-taking are necessary to establish if they are impaired in BD and to analyze the role of mood state.

A transdiagnostic comparison of affective decision-making in patients with schizophrenia, major depressive disorder, or bipolar disorder

Deficit in decision-making has been found in patients with schizophrenia (SCZ), major depressive disorder (MDD), and bipolar disorder (BD), respectively, while the common and distinct characteristics of this deficit among these patients are still unclear. The present study aimed to make a transdiagnostic comparison of the affective decision-making ability in patients with SCZ, MDD, and BD. In this study, 33 patients with SCZ, 23 patients with MDD, 29 patients with BD, and 34 healthy controls (HCs) were recruited and the Iowa Gambling Task (IGT) was used to assess the affective decision-making ability. The results showed that all three diagnostic groups tended to select the disadvantageous decks but not advantageous decks compared to HCs. For patients with SCZ, an excessive preference for the disadvantageous decks with larger-magnitude less frequent punishments (deck B) may be the main reason of the deficit in affective decision-making, while that in patients with MDD was a significantly decreased ability to choose advantageous decks on the whole but with larger-magnitude less frequent punishments (deck D). As regards patients with BD, the concurrence of more choices of deck B and fewer choices of deck D was the characteristic of the deficit in affective decision-making. Our findings suggest a common affective decision-making impairment in the context of multiple choices in patients with SCZ, MDD, and BD, while the underlying mechanisms of the impairment among these patients may be slightly different.

Characterizing decision-making and reward processing in bipolar disorder: A cluster analysis

The presence of abnormalities in emotional decision-making and reward processing among bipolar patients (BP) has been well rehearsed. These disturbances are not limited to acute phases and are common even during remission. In recent years, the existence of discrete cognitive profiles in this psychiatric population has been replicated. However, emotional decision making and reward processing domains have barely been studied. Therefore, our aim was to explore the existence of different profiles on the aforementioned cognitive dimensions in BP. The sample consisted of 126 euthymic BP. Main sociodemographic, clinical, functioning, and neurocognitive variables were gathered. A hierarchical-clustering technique was used to identify discrete neurocognitive profiles based on the performance in the Iowa Gambling Task. Afterward, the resulting clusters were compared using ANOVA or Chi-squared Test, as appropriate. Evidence for the existence of three different profiles was provided. Cluster 1 was mainly characterized by poor decision ability. Cluster 2 presented the lowest sensitivity to punishment. Finally, cluster 3 presented the best decision-making ability and the highest levels of punishment sensitivity. Comparison between the three clusters indicated that cluster 2 was the most functionally impaired group. The poorest outcomes in attention, executive function domains, and social cognition were also observed within the same group. In conclusion, similarly to that observed in "cold cognitive" domains, our results suggest the existence of three discrete cognitive profiles concerning emotional decision making and reward processing. Amongst all the indexes explored, low punishment sensitivity emerge as a potential correlate of poorer cognitive and functional outcomes in bipolar disorder.

Decision making measured by the Iowa Gambling Task in alcohol use disorder and gambling disorder: a systematic review and meta-analysis

BACKGROUND AND AIMS

Gambling disorder (GD) and alcohol use disorder (AD) have similar features, such as elevated impulsivity and decision-making deficits, which are directly linked to relapse and poor therapeutic outcomes. Our aim was to assess decision-making characteristics in GD and AD patients compared to healthy controls (HC) based on one of the most frequently used measures of decision-making: the Iowa Gambling Task (IGT).

METHODS

In our systematic literature search of three databases, we identified 1198 empirical articles that mentioned decision-making deficits with the use of the IGT in patients diagnosed with either AD or GD. Possible effects were calculated using meta-analysis. In the end, 17 studies (including 1360 participants) were suitable for inclusion in the meta-analysis reporting data for 23 group contrasts.

RESULTS

The random effects estimate indicated impaired IGT performance in both AD patients (N=500; d=-0.581, CI:-89.5<δ<-26.6%) and an even greater deficit in GD patients (N=292; d=-1.034, CI:-156.1<δ<50.7%) compared to HCs. Sampling variances were calculated for both AD (v₁=0.0056) and GD groups (v₂=0.0061), from which the z-score was calculated (z=-21.0785; p<0.05), which indicates a statistically significant difference between AD and GD groups. No significant moderating effects of age, gender or education were found.

CONCLUSIONS

There is enough evidence to support that decision-making deficit associated with addictive disorders, and that the deficit is more expressed in gambling disorder than in alcohol use disorder. Impaired decision-making plays an important part in poor therapeutic outcomes, thus provides a promising opportunity for cognitive intervention.

Structural characteristics of the brain reward circuit regions in patients with bipolar I disorder: A voxel-based morphometric study

Bipolar I disorder (BD-I) is often misdiagnosed, leading to inadequate treatment and significant disability along with reduced quality of life. Recent neural models suggest that the reward circuitry is affected in bipolar disorder. The purpose of the present study was to identify structural abnormalities in the brain reward-processing neural circuitry among patients with BD-I. 21 patients with BD-I and 21 healthy controls (HC) participated in this study. Structural magnetic resonance imaging was performed. Region-of-interest (ROI) voxel-based morphometry analysis was applied to assess the presence of structural changes between the BD-I patient group and the control group. The results of the reward circuitry ROI analysis revealed lower gray matter volumes in the left ventromedial prefrontal cortex (VMPFC), left dorsomedial prefrontal cortex (DMPFC), and left ventrolateral prefrontal cortex (VLPFC) in patients with BD-I compared to HC. Our results suggest that abnormalities in the brain reward-processing neural circuitry, especially those in the left VMPFC, left DMPFC, and left VLPFC, may play an important role in the pathophysiology of BD-I.

Reward Dysfunction in the Manic Spectrum: Unable to Win? The Use of Biographical Information to Refine Neurobiological Modeling

OBJECTIVE

The manic spectrum is thought to be characterized by a hypersensitive biobehavioral reward system, the behavioral activation system. Evidence for this framework comes from questionnaire-based, self-report data collected in cross-sectional and prospective studies of mania, mania in remission, and proneness to hypomania, and from functional neuroimaging investigations of brain reward circuit activity during incentivized choice protocols. Although heightened reward anticipation is consistently documented, the status of later goal attainment activity, hedonic responses, and satiety reactions is less clear. This report examines the status of such reward receipt processes as they operate in the manic spectrum.

METHODS

A case report of a typical subject with bipolar II disorder with a hyperthymic temperament is presented using longitudinal, biographical data.

RESULTS

Diminished reward receipt, pleasure, and satiety were demonstrated indicating impaired hedonic processing in hyperthymic temperament. This impairment indicates a dissociation between early, intensified reward pursuit processes and later, blunted, reward attainment activity.

CONCLUSIONS

The experience and neural correlates of hedonic processing may be impaired in the manic spectrum. Possible mechanisms for this impairment and its dissociation from the earlier stage of reward processing characterized by hyperactive reward pursuit are considered. Clinical reports and longitudinal, life-based follow-up can provide important data to supplement more experimentally based neurobiological models of reward dysfunction in bipolar disorders.

Reward Dysfunction in the Manic Spectrum: Unable to Win? The Use of Biographical Information to Refine Neurobiological Modeling

OBJECTIVE

The manic spectrum is thought to be characterized by a hypersensitive biobehavioral reward system, the behavioral activation system. Evidence for this framework comes from questionnaire-based, self-report data collected in cross-sectional and prospective studies of mania, mania in remission, and proneness to hypomania, and from functional neuroimaging investigations of brain reward circuit activity during incentivized choice protocols. Although heightened reward anticipation is consistently documented, the status of later goal attainment activity, hedonic responses, and satiety reactions is less clear. This report examines the status of such reward receipt processes as they operate in the manic spectrum.

METHODS

A case report of a typical subject with bipolar II disorder with a hyperthymic temperament is presented using longitudinal, biographical data.

RESULTS

Diminished reward receipt, pleasure, and satiety were demonstrated indicating impaired hedonic processing in hyperthymic temperament. This impairment indicates a dissociation between early, intensified reward pursuit processes and later, blunted, reward attainment activity.

CONCLUSIONS

The experience and neural correlates of hedonic processing may be impaired in the manic spectrum. Possible mechanisms for this impairment and its dissociation from the earlier stage of reward processing characterized by hyperactive reward pursuit are considered. Clinical reports and longitudinal, life-based follow-up can provide important data to supplement more experimentally based neurobiological models of reward dysfunction in bipolar disorders.

Impulsivity is associated with blood pressure and waist circumference among adolescents with bipolar disorder

OBJECTIVE

Cardiovascular risk factors (CVRFs) and impulsivity are common in bipolar disorder (BD), and CVRFs are also linked with impulsivity through a number of mechanisms, both behavioral and biological. This study examines the association between CVRFs and impulsivity in adolescents with BD.

METHODS

Subjects were 34 adolescents with BD and 35 healthy control (HC) adolescents. CVRFs were based on International Diabetes Federation metabolic syndrome criteria (triglycerides, high-density lipoprotein cholesterol, waist circumference, blood pressure (BP) and glucose). Impulsivity was measured using the computerized Cambridge Gambling Task (CGT). Analyses controlled for age, IQ, lifetime attention deficit hyperactivity disorder, and current antipsychotic use.

RESULTS

Adolescents with BD had higher diastolic BP (73.36 ± 9.57 mmHg vs. 67.91 ± 8.74 mmHg, U = 401.0, p = 0.03), higher triglycerides (1.13 ± 0.60 mmol/L vs. 0.78 ± 0.38 mmol/L, U = 373.5, p = 0.008), and were more likely to meet high-risk criteria for waist circumference (17.6% vs. 2.9%, p = 0.04) vs. HC. Within the BD group, CGT sub-scores were correlated with CVRFs. For example, overall proportion bet was positively correlated with systolic (r = 0.387, p = 0.026) and diastolic (ρ = 0.404, p = 0.020) BP. Quality of decision-making was negatively correlated with systolic BP (ρ = -0.401, p = 0.021) and waist circumference (ρ = -0.534, p = 0.003). Significant interactions were observed, such that BD diagnosis moderates the relationship between both waist circumference and BP with CGT sub-scores.

CONCLUSION

BP and waist circumference are associated with impulsivity in BD adolescents, but not in HC adolescents. Future studies are warranted to determine temporality and to evaluate whether optimizing CVRFs improves impulsivity among BD adolescents.

Eveningness and Its Associated Impairments in Remitted Bipolar Disorder

Sleep-wake and circadian rhythm disturbances are common in remitted bipolar disorder. These disturbances include difficulty initiating and maintaining sleep, daytime sleepiness, sleep irregularity, and a circadian tendency toward eveningness. To date, few studies have examined the impact of eveningness on impairments in remitted bipolar disorder. Ninety-eight adults diagnosed with bipolar disorder I, II, or not otherwise specified were evaluated. Hierarchical linear regression analyses showed that eveningness was associated with greater sleep-wake disturbances, more unhealthy dietary habits, worse quality of life, more impaired interpersonal relationships, and more dysfunctional sleep-related cognitions and behaviors, controlling for age, gender, and years of education. Targeted intervention on dysfunctional sleep-related cognitions and behaviors may reverse eveningness and improve functioning in bipolar disorder.

Modeling neurodevelopmental cognitive deficits in tasks with cross-species translational validity

Numerous psychiatric disorders whose cognitive dysfunction links to functional outcome have neurodevelopmental origins including schizophrenia, autism and bipolar disorder. Treatments are needed for these cognitive deficits, which require development using animal models. Models of neurodevelopmental disorders are as varied and diverse as the disorders themselves, recreating some but not all aspects of the disorder. This variety may in part underlie why purported procognitive treatments translated from these models have failed to restore functioning in the targeted patient populations. Further complications arise from environmental factors used in these models that can contribute to numerous disorders, perhaps only impacting specific domains, while diagnostic boundaries define individual disorders, limiting translational efficacy. The Research Domain Criteria project seeks to 'develop new ways to classify mental disorders based on behavioral dimensions and neurobiological measures' in hopes of facilitating translational research by remaining agnostic toward diagnostic borders derived from clinical presentation in humans. Models could therefore recreate biosignatures of cognitive dysfunction irrespective of disease state. This review highlights work within the field of neurodevelopmental models of psychiatric disorders tested in cross-species translational cognitive paradigms that directly inform this newly developing research strategy. By expounding on this approach, the hopes are that a fuller understanding of each model may be attainable in terms of the cognitive profile elicited by each manipulation. Hence, conclusions may begin to be drawn on the nature of cognitive neuropathology on neurodevelopmental and other disorders, increasing the chances of procognitive treatment development for individuals affected in specific cognitive domains.

Role of Reward Sensitivity and Processing in Major Depressive and Bipolar Spectrum Disorders

Since Costello's (1972) seminal Behavior Therapy article on loss of reinforcers or reinforcer effectiveness in depression, the role of reward sensitivity and processing in both depression and bipolar disorder has become a central area of investigation. In this article, we review the evidence for a model of reward sensitivity in mood disorders, with unipolar depression characterized by reward hyposensitivity and bipolar disorders by reward hypersensitivity. We address whether aberrant reward sensitivity and processing are correlates of, mood-independent traits of, vulnerabilities for, and/or predictors of the course of depression and bipolar spectrum disorders, covering evidence from self-report, behavioral, neurophysiological, and neural levels of analysis. We conclude that substantial evidence documents that blunted reward sensitivity and processing are involved in unipolar depression and heightened reward sensitivity and processing are characteristic of hypomania/mania. We further conclude that aberrant reward sensitivity has a trait component, but more research is needed to clearly demonstrate that reward hyposensitivity and hypersensitivity are vulnerabilities for depression and bipolar disorder, respectively. Moreover, additional research is needed to determine whether bipolar depression is similar to unipolar depression and characterized by reward hyposensitivity, or whether like bipolar hypomania/mania, it involves reward hypersensitivity.

Impulsivity predicts the onset of DSM-IV-TR or RDC hypomanic and manic episodes in adolescents and young adults with high or moderate reward sensitivity

BACKGROUND

A growing body of research suggests that bipolar disorders (BD) are associated with high impulsivity. Using a multi-method approach, the current study provided the first examination of the hypothesis that impulsivity would prospectively predict shorter time to onset of DSM-IV-TR or RDC hypomanic or manic episodes in a sample selected based on reward sensitivity, a biobehavioral trait shown to predict onset and course of BD.

METHODS

163 participants with high reward sensitivity and 114 participants with moderate reward sensitivity were followed every six months for an average of 2.68 years. Participants completed the Barratt Impulsiveness Scale - Version 11 (BIS-11), Balloon Analog Risk Task (BART), Beck Depression Inventory, Altman Self-Rating Mania Scale, and an expanded Schedule for Affective Disorders and Schizophrenia (exp-SADS) - Lifetime Version at baseline and were followed prospectively with the exp-SADS - Change Version to assess onset of hypomanic or manic episodes and treatment seeking for mood problems.

RESULTS

Cox proportional hazard regression analyses indicated that impulsivity as measured by a behavioral task (BART; OR=1.04, p=.03) and a self-report measure (BIS-11 Attentional Impulsiveness subscale; OR=1.16, p=.01) predicted shorter time to hypomania/mania onset, after controlling for baseline depressive and manic symptoms, family history of mood disorder, treatment seeking for mood problems, and reward sensitivity.

LIMITATIONS

The study was limited by non-comprehensive assessment of impulsivity and unknown generalizability to clinical samples.

CONCLUSIONS

Impulsivity confers vulnerability to hypomania or mania. Future studies would benefit from considering how impulsivity can be integrated into existing biopsychosocial models of BD.

Nicotine-dopamine-transporter interactions during reward-based decision making

Our everyday-life comprises a multitude of decisions that we take whilst trying to maximize advantageous outcomes, limit risks and update current needs. The cognitive processes that guide decision making as well as the brain circuits they are based on are only poorly understood. Numerous studies point to a potential role of dopamine and nicotine in decision making but less is known about their interactions. Here, 26 healthy male subjects performed the Iowa Gambling Task (IGT) in two sessions following the administration of either nicotine or placebo. Striatal dopamine transporter (DAT) binding was measured by single-photon emission computed tomography (SPECT). Results indicate that lower DAT levels were associated with better performance in the IGT (p=0.0004). Cognitive modelling analysis using the prospect valence learning (PVL) model indicated that low DAT subjects' performance deteriorated following nicotine administration as indicated by an increased learning rate and a decreased response consistency. Our results shed light on the neurochemistry underlying reward-based decision making in humans by demonstrating a significant interaction between nicotine and the DAT. The observed interaction is consistent with the hypothesized associations between DAT expression and extracellular dopamine levels, suggestive of an inverted U-shape relationship between baseline dopamine and magnitude in response to a pro-dopaminergic compound. Our findings are of particular interest in the context of psychiatric disorders where aberrant decision making represents a part of the core symptomatology, such as addiction, schizophrenia or depression.

The development and course of bipolar spectrum disorders: an integrated reward and circadian rhythm dysregulation model

In this article, we present and review the evidence for two major biopsychosocial theories of the onset and course of bipolar spectrum disorders (BSDs) that integrate behavioral, environmental, and neurobiological mechanisms: the reward hypersensitivity and the social/circadian rhythm disruption models. We describe the clinical features, spectrum, age of onset, and course of BSDs. We then discuss research designs relevant to demonstrating whether a hypothesized mechanism represents a correlate, vulnerability, or predictor of the course of BSDs, as well as important methodological issues. We next present the reward hypersensitivity model of BSD, followed by the social/circadian rhythm disruption model of BSD. For each model, we review evidence regarding whether the proposed underlying mechanism is associated with BSDs, provides vulnerability to the onset of BSDs, and predicts the course of BSDs. We then present a new integrated reward/circadian rhythm (RCR) dysregulation model of BSD and discuss how the RCR model explains the symptoms, onset, and course of BSDs. We end with recommendations for future research directions.