Decreased density of the platelet serotonin transporter in pathological gamblers

Is there a relationship between morphological and functional platelet changes and depressive disorder?

BACKGROUND

Blood platelets, due to shared biochemical and functional properties with presynaptic serotonergic neurons, constituted, over the years, an attractive peripheral biomarker of neuronal activity. Therefore, the literature strongly focused on the investigation of eventual structural and functional platelet abnormalities in neuropsychiatric disorders, particularly in depressive disorder. Given their impact in biological psychiatry, the goal of the present paper was to review and critically analyze studies exploring platelet activity, functionality, and morpho-structure in subjects with depressive disorder.

METHODS

According to the PRISMA guidelines, we performed a systematic review through the PubMed database up to March 2020 with the search terms: (1) platelets in depression [Title/Abstract]"; (2) "(platelets[Title]) AND depressive disorder[Title/Abstract]"; (3) "(Platelet[Title]) AND major depressive disorder[Title]"; (4) (platelets[Title]) AND depressed[Title]"; (5) (platelets[Title]) AND depressive episode[Title]"; (6) (platelets[Title]) AND major depression[Title]"; (7) platelet activation in depression[All fields]"; and (8) platelet reactivity in depression[All fields]."

RESULTS

After a detailed screening analysis and the application of specific selection criteria, we included in our review a total of 106 for qualitative synthesis. The studies were classified into various subparagraphs according to platelet characteristics analyzed: serotonergic system (5-HT2A receptors, SERT activity, and 5-HT content), adrenergic system, MAO activity, biomarkers of activation, responsivity, morphological changes, and other molecular pathways.

CONCLUSIONS

Despite the large amount of the literature examined, nonunivocal and, occasionally, conflicting results emerged. However, the findings on structural and metabolic alterations, modifications in the expression of specific proteins, changes in the aggregability, or in the responsivity to different pro-activating stimuli, may be suggestive of potential platelet dysfunctions in depressed subjects, which would result in a kind of hyperreactive state. This condition could potentially lead to an increased cardiovascular risk. In line with this hypothesis, we speculated that antidepressant treatments would seem to reduce this hyperreactivity while representing a potential tool for reducing cardiovascular risk in depressed patients and, maybe, in other neuropsychiatric conditions. However, the problem of the specificity of platelet biomarkers is still at issue and would deserve to be deepened in future studies.

Mindfulness, Age and Gender as Protective Factors Against Psychological Distress During COVID-19 Pandemic

OBJECTIVE

Mindfulness disposition is associated with various psychological factors and prevents emotional distress in chronic diseases. In the present study, we analyzed the key role of mindfulness dispositions in protecting the individual against psychological distress consequent to COVID-19 social distancing and quarantining.

METHODS

An online survey was launched on March 13, 2020, with 6,412 responses by April 6, 2020. Socio-demographic information, exposure to the pandemic, and quarantining were assessed together with psychological distress and mindfulness disposition. Multivariate linear regression analysis was performed to study the influence of predictive factors on psychological distress and quality of life in Italian responders during the early days of lockdown. Pearson correlations were calculated to study the relationship between mindfulness and psychiatric symptoms.

RESULTS

Multivariate linear regression run on socio-demographics, COVID-19-related variables, and mindfulness disposition as moderators of overall psychological distress showed that mindfulness was the best predictor of psychological distress (β = -0.504; p < 0.0001). High negative correlations were found between mindfulness disposition and the overall Global Severity Index (r = -0.637; p < 0.0001), while moderate to high associations were found between mindfulness and all SCL-90 sub-scales.

DISCUSSION

Findings showed that high dispositional mindfulness enhances well-being and helps in dealing with stressful situations such as the COVID-19 pandemic. Mindfulness-based mental training could represent an effective intervention to stem post-traumatic psychopathological beginnings and prevent the onset of chronic mental disorders.

Retrospective Analyses of Psychological Distress and Defense Style Among Cancer Patients

OBJECTIVE

Psychological distress is common in cancer patients during the diagnostic phase. Research demonstrated that anxiety, depression and defense mechanisms may influence physical and psychological well-being in patients with malignant tumors. The present retrospective study investigated the associations between clinical and psychological characteristics of cancer patients waiting for the diagnosis, focusing on metastatic cancer (MC) and breast cancer (BC).

METHOD

Patients with a new diagnosis of cancer referring to a Clinical Oncology Unit in Central Italy were interviewed during the 2017 for psychological assessment. Double-blind information about anxiety, depression, sleep disorders, defense style, and cancer diagnosis were available for the 567 patients included in this study. T-test, chi-squared and regression analyses were performed to detect associations between psychological variables and the presence of metastasis (MC) in the whole sample and in the subgroup of breast cancer (BC) patients.

RESULTS

Female gender and younger age were associated with anxiety, depression, and maladaptive defense style. A significant positive relationship was found between presence of metastasis and symptoms of anxiety. Depression resulted significantly more frequent in BC, while there was a trend close to statistical significance in MC. Immature defense style was widely used by BC women, with a score close to statistical significance.

CONCLUSIONS

This retrospective study provided empirical evidence of the relationship between psychological functioning and clinical characteristics of cancer. In line with previous research, our findings confirmed the peculiar psychological functioning of BC patients. Further investigations are needed to understand how the diagnosis of cancer may influence the individual psychological functioning and vice versa.

Mindfulness, Compassion, and Self-Compassion Among Health Care Professionals: What's New? A Systematic Review

Health care professionals (HCPs) are a population at risk for high levels of burnout and compassion fatigue. The aim of the present systematic review was to give an overview on recent literature about mindfulness and compassion characteristics of HCPs, while exploring the effectiveness of techniques, involving the two aspects, such as MBSR or mindfulness intervention and compassion fatigue-related programs. A search of databases, including PubMed and PsycINFO, was conducted following the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) guidelines and the methodological quality for this systematic review was appraised using AMSTAR-2 (A MeaSurement Tool to Assess systematic Reviews-2). The number of articles that met the inclusion criteria was 58 (4 RCTs, 24 studies with pre-post measurements, 12 cross-sectional studies, 11 cohort studies and 7 qualitative studies). MBSR intervention was effective at improving, and maintaining, mindfulness and self-compassion levels and to improve burnout, depression, anxiety, stress. The most frequently employed interventional strategies were mindfulness-related trainings that were effective at improving mindfulness and self-compassion, but not compassion fatigue, levels. Compassion-related interventions have been shown to improve self-compassion, mindfulness and interpersonal conflict levels. Mindfulness was effective at improving negative affect and compassion fatigue, while compassion satisfaction may be related to cultivation of positive affect. This systematic review summarized the evidence regarding mindfulness- and compassion-related qualities of HCPs as well as potential effects of MBSR, mindfulness-related and compassion-related interventions on professionals' psychological variables like mindfulness, self-compassion and quality of life. Combining structured mindfulness and compassion cultivation trainings may enhance the effects of interventions, limit the variability of intervention protocols and improve data comparability of future research.

Psychological Impact of Coronavirus Disease 2019 Among Italians During the First Week of Lockdown

Pandemics and government-mandated quarantining measures have a substantial impact on mental health. This study investigated the psychological impact of the coronavirus disease 2019 (COVID-19) crisis on Italian residents during the first week of government-imposed lockdown and the role of defense mechanisms as protective factors against distress. In this cross-sectional study, 5,683 Italians responded to an online survey assessing socio-demographics, overall psychological distress, post-traumatic symptoms, and defense mechanisms using validated measures as the Symptom Checklist-90 (SCL-90), the Impact of Event Scale-Revised (IES-R), and the Defense Mechanisms Rating Scale-Self-Report-30 (DMRS-SR-30). Data were collected from March 13 to March 18, within the first week of lockdown in Italy. Results showed that younger age and female gender were associated with increased psychological distress. Having positive cases nearby, more days on lockdown, and having to relocate were also associated with greater distress. Higher overall defensive functioning (ODF) was associated with lower levels of depression (r = -.44, 95% CI -0.48, -0.40), anxiety (r = -.38, 95% CI -0.42, -0.35), and post-traumatic stress symptoms (PTSS) (r = -.34, 95% CI -0.38, -0.30). Conversely, less adaptive defensive functioning was related to greater affective distress across all domains. Each increased unit of ODF decreased the chances of developing post-traumatic stress symptoms (PTSS) by 71% (odds ratio = 0.29, p < 0.001, 95% CI.026,.032). The psychological impact of COVID-19 among Italians during the early weeks of government lockdown has been significant. The pandemic continues to have extraordinary mental health impact as it moves across the globe. Given the salience of defensive functioning in psychological distress, consideration of interventions that foster the use of more adaptive defenses may be an important component of building resilience amidst a pandemic.

Problematic Internet Use in University Students Attending Three Superior Graduate Schools in Italy: Is Autism Spectrum Related to Suicide Risk?

Background: Over the past decades, problematic internet use (PIU) has dramatically increased, especially among young people. PIU has been recently associated with autism spectrum disorder (ASD) and autistic traits. Subjects with PIU report an increased suicidal risk and the same has been demonstrated among patients with ASD. The aim of this study was to investigate putative PIU rates among students and explore the correlation between autistic traits and suicide risk. Methods: A sample of 178 high achieving university students was assessed by means of the Adult Autism Subthreshold Spectrum (AdAS Spectrum), Autism Quotient questionnaire (AQ). Suicide risk was investigated by some specific items of the Trauma and Loss Spectrum-Self Report (TALS-SR) and putative PIU was identified on the basis of a specific AdAS Spectrum item. Results: 27.5% subjects reporting putative PIU. This subgroup showed higher scores in all domains of AdAS Spectrum and AQ compared with others. Students with putative PIU showed a significant correlation between suicide risk and the non-verbal communication domain of the AdAS Spectrum and the Social skills domain of the AQ. Conclusions: We found that students with PIU show higher levels of autistic traits compared to those without PIU. A significant correlation was found between autistic traits and suicide risk.

Polysubstance and Behavioral Addictions in a Patient with Bipolar Disorder: Role of Lifetime Subthreshold Autism Spectrum

This case report draws attention to the potential relevance of undetected autism spectrum symptoms in a bipolar patient with high work functioning showing a peculiar addictive profile with impulsive and antisocial behaviors. A 23-year-old man with a diagnosis of Bipolar Disorder (BD) and Substance Use Disorder (SUD) was hospitalized at the Psychiatric Clinic of the University of Pisa for diuretics and β-2 adrenergic agonist abuse in a remission phase of benzodiazepines and substance abuse. He reported a history of behavioral addictions in the framework of a global high work functioning with particular skills in computer science. When assessed for adult autism spectrum symptoms, despite not fulfilling a DSM-5 diagnosis of Autism Spectrum Disorder (ASD), he reported a score of 93/240 at the Ritvo Autism and Asperger Diagnostic Scale (RAADS-r) and of 88/160 at the Adult Autism Subthreshold Spectrum (AdAS Spectrum), both indicative of ASD. We argue the possible role of adult subthreshold autism spectrum features, generally disregarded in adult psychiatry, in the peculiar addictive profile developed by this patient with BD that may deserve appropriate treatment.

Similarities and Differences in Neurobiology

Substance addiction is a chronic, relapsing brain disease characterized by compulsive drug seeking and use despite harmful consequences. Non-substance addiction is defined recently that people may compulsively engage in an activity despite any negative consequences to their lives. Despite differences with respect to their addictive object, substance addiction and non-substance addiction may share similarities with respect to biological, epidemiological, clinical, genetic and other features. Here we review the similarities and differences in neurobiology between these two addictions with a focus on dopamine, serotonin, opioid, glutamate and norepinephrine systems. Studies suggest the involvement of all these systems in both substance addiction and non-substance addiction while differences may exist with respect to their contributions.

Down-regulation of serotonin and dopamine transporter genes in individual rats expressing a gambling-prone profile: A possible role for epigenetic mechanisms

Gambling Disorder (GD) is characterized by excessive gambling despite adverse consequences on individual functioning. In spite of some positive findings, it is difficult to draw any conclusion on the genetics of GD. Indeed, beyond DNA sequence variation, other regulatory mechanisms (like those that engage epigenetics) may explain gene alterations in this addictive disease. Wistar male rats underwent an operant task for the evaluation of individual propensity to gamble. Few rats, after having learnt to prefer nose-poking for a large over a small food reward, were sacrificed to obtain a baseline profile of gene expression at both central and peripheral levels. In the remaining rats, probability of occurrence of large-reward delivery decreased progressively to very low levels. Thus, rats were faced with temptation to "gamble", i.e. to nose-poke for a binge reward, whose delivery was omitted the majority of times. After 3weeks of testing, rats showing a clear-cut profile of either gambling proneness or aversion were selected and sacrificed after the last session. A selective down-regulation of i) serotonin transporter in prefrontal cortex, ii) tyrosine hydroxylase in ventral striatum, iii) dopamine transporter in lymphocytes was evidenced in "gambler" vs "non-gambler" rats. The exposure to such operant task (compared to home-cage alone) modulated ventrostriatal but not prefrontal genes. A consistent increase of DNA methylation, in one specific CpG site at serotonin transporter gene, was evident in prefrontal cortex of "gambler" rats. Elucidation of epigenetic changes occurring during GD progression may pave the way to the development of new therapeutic strategies through specific modulation of epigenetic factors.

Behavioral addictions: a novel challenge for psychopharmacology

Although addictive syndromes have been traditionally related to substance-use disorders, during the last few decades a novel addictive group, including the so-called "behavioral or no-drug addictions," has been recognized and has attracted increasing attention for its relevant social impact. This group includes pathological gambling, compulsive shopping, TV/Internet/social network/videogame addictions, workaholism, sex and relationship addictions, orthorexia, and overtraining syndrome. Substance and behavioral addictions show similar phenomenological features, such as craving, dependence, tolerance, and abstinence, and perhaps they share a common possible pathophysiology. It is, however, controversial whether all or at least some of them should be considered real disorders or just normal, albeit extreme, behaviors. The aim of this article is to review current data on pharmacological treatment of behavioral addictions. As no specific and validated treatment algorithms are currently available, only an improved knowledge on their psychopathological, clinical, and neurobiological features may have relevant implications for more focused preventive and therapeutic strategies.

Citalopram-associated gambling: a case report

Pathological gambling behaviour is a side effect of dopaminergic drugs used in Parkinson's disease, but has seldom been reported with selective serotonin reuptake inhibitors. A 58-years-old woman with somatisation disorder since the age of 20 and recent-onset major depression (at 54 years) received 40 mg/day intravenous citalopram, thereafter switching to the same dose of oral citalopram to treat her comorbid psychiatric disorders after showing poor response to paroxetine for one year. Her anxious and depressive symptoms were moderately reduced after 7 months of oral citalopram, but simultaneously, the patient admitted gambling. We gradually discontinued citalopram and introduced pregabalin and alprazolam; this was followed by a reduction of gambling compulsions, but the somatisation and depressive symptoms did not further improve. Pathological gambling may be mediated by an interplay of 5-HT1A serotonergic and D2 dopaminergic mechanisms. Citalopram affects both these mechanisms in areas that were shown to be involved in gambling behaviour, but while dopaminergic effects of citalopram appear to be consistent with the induction of gambling, its serotonergic mechanisms are rather inconsistent. In our patient, mood destabilisation induced by citalopram may have contributed to the first onset of pathological gambling.

Multiple modes of impulsivity in Parkinson's disease

Cognitive problems are a major factor determining quality of life of patients with Parkinson's disease. These include deficits in inhibitory control, ranging from subclinical alterations in decision-making to severe impulse control disorders. Based on preclinical studies, we proposed that Parkinson's disease does not cause a unified disorder of inhibitory control, but rather a set of impulsivity factors with distinct psychological profiles, anatomy and pharmacology. We assessed a broad set of measures of the cognitive, behavioural and temperamental/trait aspects of impulsivity. Sixty adults, including 30 idiopathic Parkinson's disease patients (Hoehn and Yahr stage I–III) and 30 healthy controls, completed a neuropsychological battery, objective behavioural measures and self-report questionnaires. Univariate analyses of variance confirmed group differences in nine out of eleven metrics. We then used factor analysis (principal components method) to identify the structure of impulsivity in Parkinson's disease. Four principal factors were identified, consistent with four different mechanisms of impulsivity, explaining 60% of variance. The factors were related to (1) tests of response conflict, interference and self assessment of impulsive behaviours on the Barrett Impulsivity Scale, (2) tests of motor inhibitory control, and the self-report behavioural approach system, (3) time estimation and delay aversion, and (4) reflection in hypothetical scenarios including temporal discounting. The different test profiles of these four factors were consistent with human and comparative studies of the pharmacology and functional anatomy of impulsivity. Relationships between each factor and clinical and demographic features were examined by regression against factor loadings. Levodopa dose equivalent was associated only with factors (2) and (3). The results confirm that impulsivity is common in Parkinson's disease, even in the absence of impulse control disorders, and that it is not a unitary phenomenon. A better understanding of the structure of impulsivity in Parkinson's disease will support more evidence-based and effective strategies to treat impulsivity.

A targeted review of the neurobiology and genetics of behavioural addictions: an emerging area of research

This review summarizes neurobiological and genetic findings in behavioural addictions, draws parallels with findings pertaining to substance use disorders, and offers suggestions for future research. Articles concerning brain function, neurotransmitter activity, and family history and (or) genetic findings for behavioural addictions involving gambling, Internet use, video game playing, shopping, kleptomania, and sexual activity were reviewed. Behavioural addictions involve dysfunction in several brain regions, particularly the frontal cortex and striatum. Findings from imaging studies incorporating cognitive tasks have arguably been more consistent than cue-induction studies. Early results suggest white and grey matter differences. Neurochemical findings suggest roles for dopaminergic and serotonergic systems, but results from clinical trials seem more equivocal. While limited, family history and genetic data support heritability for pathological gambling and that people with behavioural addictions are more likely to have a close family member with some form of psychopathology. Parallels exist between neurobiological and genetic and family history findings in substance and nonsubstance addictions, suggesting that compulsive engagement in these behaviours may constitute addictions. To date, findings are limited, particularly for shopping, kleptomania, and sexual behaviour. Genetic understandings are at an early stage. Future research directions are offered.

Pathological gambling: a systematic review of biochemical, neuroimaging, and neuropsychological findings

Pathological gambling is an emerging psychiatric disorder that has recently gained much attention because of its increasing prevalence and devastating personal, familial, and social consequences. Although its pathophysiology is largely unknown, the shared similarities with both addiction and obsessive-compulsive spectrum disorders have suggested the possibility of common psychobiological substrates. As with many other psychiatric disorders, it is believed that pathological gambling may result from the interplay between individual vulnerability and environmental factors. The aim of this article is to offer a comprehensive review of the main neurobiological aspects of pathological gambling, with particular attention to neuropsychological and related findings. A deeper understanding of the biological correlates of pathological gambling is required in order to develop effective treatment strategies.

Similarities and differences between pathological gambling and substance use disorders: a focus on impulsivity and compulsivity

RATIONALE

Pathological gambling (PG) has recently been considered as a "behavioral" or nonsubstance addiction. A comparison of the characteristics of PG and substance use disorders (SUDs) has clinical ramifications and could help advance future research on these conditions. Specific relationships with impulsivity and compulsivity may be central to understanding PG and SUDs.

OBJECTIVES

This review was conducted to compare and contrast research findings in PG and SUDs pertaining to neurocognitive tasks, brain function, and neurochemistry, with a focus on impulsivity and compulsivity.

RESULTS

Multiple similarities were found between PG and SUDs, including poor performance on neurocognitive tasks, specifically with respect to impulsive choice and response tendencies and compulsive features (e.g., response perseveration and action with diminished relationship to goals or reward). Findings suggest dysfunction involving similar brain regions, including the ventromedial prefrontal cortex and striatum and similar neurotransmitter systems, including dopaminergic and serotonergic. Unique features exist which may in part reflect influences of acute or chronic exposures to specific substances.

CONCLUSIONS

Both similarities and differences exist between PG and SUDs. Understanding these similarities more precisely may facilitate treatment development across addictions, whereas understanding differences may provide insight into treatment development for specific disorders. Individual differences in features of impulsivity and compulsivity may represent important endophenotypic targets for prevention and treatment strategies.

Rodent versions of the iowa gambling task: opportunities and challenges for the understanding of decision-making

Impaired decision-making is a core problem in several psychiatric disorders including attention-deficit/hyperactivity disorder, schizophrenia, obsessive–compulsive disorder, mania, drug addiction, eating disorders, and substance abuse as well as in chronic pain. To ensure progress in the understanding of the neuropathophysiology of these disorders, animal models with good construct and predictive validity are indispensable. Many human studies aimed at measuring decision-making capacities use the Iowa gambling task (IGT), a task designed to model everyday life choices through a conflict between immediate gratification and long-term outcomes. Recently, new rodent models based on the same principle have been developed to investigate the neurobiological mechanisms underlying IGT-like decision-making on behavioral, neural, and pharmacological levels. The comparative strengths, as well as the similarities and differences between these paradigms are discussed. The contribution of these models to elucidate the neurobehavioral factors that lead to poor decision-making and to the development of better treatments for psychiatric illness is considered, along with important future directions and potential limitations.

A(2A) adenosine receptor binding parameters in platelets from patients affected by pathological gambling

BACKGROUND/AIMS

A structural and functional interaction between A(2A) adenosine receptors and D(2) dopamine receptors has been implicated in the pathophysiology of impulse control disorders. The aim of this study was to use platelet membranes to assess A(2A) adenosine receptor affinity and density in patients affected by pathological gambling (PG; which is classified as a specific impulse control disorder) with respect to those of control subjects.

METHODS

Twelve drug-free PG patients and 12 age- and sex-matched healthy controls were enrolled in the study. PG was diagnosed according to the Structured Clinical Interview for DSM-IV - Patient Version 2.0 and the South Oaks Gambling Screen. A(2A) adenosine receptor binding parameters were evaluated using a [(3)H]ZM(241385) binding assay; affinity and density (B(max)) were determined by means of saturation binding studies with platelet membranes.

RESULTS

The A(2A) adenosine receptor binding affinity was found to be significantly higher in patients affected by PG than in healthy subjects; in contrast, no significant differences in B(max) were observed between the 2 groups.

CONCLUSIONS

The elevated A(2A) adenosine receptor binding affinity in platelets from PG patients with respect to control subjects demonstrates for the first time a change in adenosine receptor parameters, and it suggests the involvement of the adenosine system in this pathology. The previously demonstrated hyperactivity of the dopamine system in PG may modulate the A(2A) adenosine receptor, supporting a role for this receptor as a peripheral marker of dopamine dysfunction. Because it is not possible to directly measure the D(2) dopamine receptor in human platelets, these data are particularly relevant to the detection of dopamine dysfunction.

Contributions of serotonin in addiction vulnerability

The serotonin (5-hydroxytryptamine; 5-HT) system has long been associated with mood and its dysregulation implicated in the pathophysiology of mood and anxiety disorders. While modulation of 5-HT neurotransmission by drugs of abuse is also recognized, its role in drug addiction and vulnerability to drug relapse is a more recent focus of investigation. First, we review preclinical data supporting the serotonergic raphe nuclei and their forebrain projections as targets of drugs of abuse, with emphasis on the effects of psychostimulants, opioids and ethanol. Next, we examine the role of 5-HT receptors in impulsivity, a core behavior that contributes to the vulnerability to addiction and relapse. Finally, we discuss evidence for serotonergic dysregulation in comorbid mood and addictive disorders and suggest novel serotonergic targets for the treatment of addiction and the prevention of drug relapse.

Serotonergic and dopaminergic modulation of gambling behavior as assessed using a novel rat gambling task

Pathological gambling (PG) is characterized by persistent, maladaptive gambling behavior, which disrupts personal and professional life. Animal models of gambling behavior could make a significant contribution to improving our understanding of the neural and neurochemical basis of gambling, and the treatment of PG. When gambling, failing to win critically results in the loss of resources wagered as well as the absence of additional gain. Here, we have incorporated these concepts into a novel rat gambling task (rGT), based, in part, on the 'Iowa' gambling task (IGT) commonly used clinically to measure gambling-like behavior. Rats choose among four different options to earn as many sugar pellets as possible within 30 min. Each option is associated with the delivery of a different amount of reward, but also with a different probability and duration of punishing time-out periods during which reward cannot be earned. The schedules are designed such that persistent choice of options linked with larger rewards result in fewer pellets earned per unit time. Rats learn to avoid these risky options to maximize their earnings, comparable with the optimal strategy in the IGT. Both d-amphetamine and the 5-HT(1A) receptor agonist, 8-OH-DPAT, impaired task performance. In contrast, the dopamine D(2) receptor antagonist, eticlopride, improved performance, whereas the D(1) receptor antagonist, SCH23390, had no effect. These data suggest that both serotonergic and dopaminergic agents can impair and improve gambling performance, and indicate that the rGT will be a useful tool to study the biological basis of gambling.

Serotonin transporter expression is predicted by early life stress and is associated with disinhibited behavior in infant rhesus macaques

Serotonin transporter (5-HTT) expression patterns may contribute to the risk for adverse psychological outcomes following early life stress. The present study investigated whether two types of early life stress, maternal and social aggression, and a serotonin transporter gene promoter polymorphism (rh5-HTTLPR) predicted lower post-stressor peripheral blood mononuclear cell (PBMC) 5-HTT expression in infant rhesus macaques. We further probed the relationships among these factors and infant behavioral disinhibition within a stressful situation. Fifty-three infants residing with mothers in large, complex social groups were observed over the first 12 postnatal weeks, during which time the rate of aggression received by the infant from their mothers and social group members was recorded. At 90-120 days of age, infants underwent a 25-h maternal separation/biobehavioral assessment, which included standardized behavioral assessments and blood sampling. Infants' rh5-HTTLPR genotypes were determined, and infant 5-HTT expression was quantified from PBMCs collected 8 h after separation. Receipt of aggression from the mother, but not from social group members, was associated with lower post-stressor 5-HTT expression. Lower post-stressor 5-HTT expression, but not receipt of aggression, was associated with disinhibited behavior during assessment. Rh5-HTTLPR genotype was unrelated to any measure. We conclude that 5-HTT regulation is linked with specific, presumably stressful early experiences in infant rhesus macaques. Further, 5-HTT expression predicted behavioral disinhibition, presumably via parallel processes that operate in the brain.