The serotonin transporter promoter variant (5-HTTLPR), stress, and depression meta-analysis revisited: evidence of genetic moderation

Epidemiology and genetics of common mental disorders in the general population: the PEGASUS-Murcia project

BACKGROUND

Multidisciplinary collaboration between clinicians, epidemiologists, neurogeneticists and statisticians on research projects has been encouraged to improve our knowledge of the complex mechanisms underlying the aetiology and burden of mental disorders. The PEGASUS-Murcia (Psychiatric Enquiry to General Population in Southeast Spain-Murcia) project was designed to assess the prevalence of common mental disorders and to identify the risk and protective factors, and it also included the collection of biological samples to study the gene-environmental interactions in the context of the World Mental Health Survey Initiative.

METHODS AND ANALYSIS

The PEGASUS-Murcia project is a new cross-sectional face-to-face interview survey based on a representative sample of non-institutionalised adults in the Region of Murcia (Mediterranean Southeast, Spain). Trained lay interviewers used the latest version of the computer-assisted personal interview of the Composite International Diagnostic Interview (CIDI 3.0) for use in Spain, specifically adapted for the project. Two biological samples of buccal mucosal epithelium will be collected from each interviewed participant, one for DNA extraction for genomic and epigenomic analyses and the other to obtain mRNA for gene expression quantification. Several quality control procedures will be implemented to assure the highest reliability and validity of the data. This article describes the rationale, sampling methods and questionnaire content as well as the laboratory methodology.

ETHICS AND DISSEMINATION

Informed consent will be obtained from all participants and a Regional Ethics Research Committee has approved the protocol. Results will be disseminated in peer-reviewed publications and presented at the national and the international conferences.

DISCUSSION

Cross-sectional studies, which combine detailed personal information with biological data, offer new and exciting opportunities to study the gene-environmental interactions in the aetiology of common mental disorders in representative samples of the general population. A collaborative multidisciplinary research approach offers the potential to advance our knowledge of the underlying complex interactions and this opens the field for further innovative study designs in psychiatric epidemiology.

Stress, serotonin, and hippocampal neurogenesis in relation to depression and antidepressant effects

Chronic stressful life events are risk factors for developing major depression, the pathophysiology of which is strongly linked to impairments in serotonin (5-HT) neurotransmission. Exposure to chronic unpredictable stress (CUS) has been found to induce depressive-like behaviours, including passive behavioural coping and anhedonia in animal models, along with many other affective, cognitive, and behavioural symptoms. The heterogeneity of these symptoms represents the plurality of corticolimbic structures involved in mood regulation that are adversely affected in the disorder. Chronic stress has also been shown to negatively regulate adult hippocampal neurogenesis, a phenomenon that is involved in antidepressant effects and regulates subsequent stress responses. Although there exists an enormous body of data on stress-induced alterations of 5-HT activity, there has not been extensive exploration of 5-HT adaptations occurring presynaptically or at the level of the raphe nuclei after exposure to CUS. Similarly, although hippocampal neurogenesis is known to be negatively regulated by stress and positively regulated by antidepressant treatment, the role of neurogenesis in mediating affective behaviour in the context of stress remains an active area of investigation. The goal of this review is to link the serotonergic and neurogenic hypotheses of depression and antidepressant effects in the context of stress. Specifically, chronic stress significantly attenuates 5-HT neurotransmission and 5-HT1A autoreceptor sensitivity, and this effect could represent an endophenotypic hallmark for mood disorders. In addition, by decreasing neurogenesis, CUS decreases hippocampal inhibition of the hypothalamic-pituitary-adrenal (HPA) axis, exacerbating stress axis overactivity. Similarly, we discuss the possibility that adult hippocampal neurogenesis mediates antidepressant effects via the ventral (in rodents; anterior in humans) hippocampus' influence on the HPA axis, and mechanisms by which antidepressants may reverse chronic stress-induced 5-HT and neurogenic changes. Although data are as yet equivocal, antidepressant modulation of 5-HT neurotransmission may well serve as one of the factors that could drive neurogenesis-dependent antidepressant effects through these stress regulation-related mechanisms.

The 5-HTTLPR polymorphism and posttraumatic stress disorder: a meta-analysis

Environmental and genetic factors contribute to the development of posttraumatic stress disorder (PTSD). Variation in the 5-HTTLPR polymorphism of the serotonin transporter gene has been hypothesized to affect risk for PTSD. With the aim of investigating this association, we conducted a meta-analysis to shed light on prior controversial results and increase statistical power to detect smaller effect sizes. PubMed and ISI databases were searched for studies published until December 2012. Twelve studies have been included, all based on trauma-exposed samples. Data were analyzed with Cochrane Collaboration Review Manager Software (Version 5). Quality and publication bias were assessed. Metaregressions were performed using Comprehensive Meta-Analysis software, Version 2. Taking into account all studies, no association was found between 5-HTTLPR and PTSD (p = .10), with evidence of between-study heterogeneity, which could be partly explained by gender differences. In sensitivity analyses, we found an association between SS genotype and PTSD in high trauma-exposed participants (p < .001). To be a carrier of the SS genotype seems to represent a risk factor for PTSD in high trauma exposure. Further studies focusing on Gene × Environment interactions are needed to better understand the role of this polymorphism in PTSD.

How the cerebral serotonin homeostasis predicts environmental changes: a model to explain seasonal changes of brain 5-HTT as intermediate phenotype of the 5-HTTLPR

Molecular imaging studies with positron emission tomography have revealed that the availability of serotonin transporter (5-HTT) in the human brain fluctuates over the course of the year. This effect is most pronounced in carriers of the short allele of the 5-HTT promoter region (5-HTTLPR), which has in several previous studies been linked to an increased risk to develop mood disorders. We argue that long-lasting fluctuations in the cerebral serotonin transmission, which is regulated via the 5-HTT, are responsible for mediating responses to environmental changes based on an assessment of the expected "safety" of the environment; this response is obtained in part through serotonergic modulation of the hypothalamic-pituitary-adrenal (HPA) axis. We posit that the intermediate phenotype of the s-allele may properly be understood as mediating a trade-off, wherein increased responsiveness of cerebral serotonin transmission to seasonal and other forms of environmental change imparts greater behavioral flexibility, at the expense of increased vulnerability to stress. This model may explain the somewhat higher prevalence of the s-allele in some human populations dwelling at geographic latitudes with pronounced seasonal climatic changes, while this hypothesis does not rule out that genetic drift plays an additional or even exclusive role. We argue that s-allele manifests as an intermediate phenotype in terms of an increased responsiveness of the 5-HTT expression to number of daylight hours, which may serve as a stable surrogate marker of other environmental factors, such as availability of food and safety of the environment in populations that live closer to the geographic poles.

The psychodynamic psychotherapist's guide to the interaction among sex, genes, and environmental adversity in the etiology of depression for women

From menarche to menopause, women are highly vulnerable to major depression. While biological and psychosocial differences between men and women have been established, the reason for the preponderance of depression in women has yet to be fully elucidated. Women may be predisposed to depressive illness because of biological factors related to brain structure, function, and the impact of reproductive life stages. They may also be at increased risk because they are differentially disadvantaged with respect to environmental stressors including interpersonal violence, socioeconomic instability, and caregiving burden, among others. However, not all women develop depression, nor do all individuals who suffer from adverse life events. This narrative review focuses on emerging research related to the interaction between sex, genetics, and environmental factors that may help offer clues about why some individuals suffer from depression, and why others may be resilient to this outcome. While many questions remain unanswered, the psychodynamic psychotherapist can use this information to help patients suffering from depression understand some of the complexities of the determinants of risk and resilience, with the goal of moving forward toward recovery.

Serotonin transporter genotype (5-HTTLPR) and electrocortical responses indicating the sensitivity to negative emotional cues

Growing literature indicates that emotional reactivity and regulation are strongly linked to genetic modulation of serotonergic neurotransmission. However, until now, most studies have focused on the relationship between genotypic markers, in particular the serotonin transporter-linked polymorphic region (5-HTTLPR), and neural structures using MRI. The current study aimed to bridge the gap between the relevant MRI literature on the effects of the 5-HTTLPR genotype and the research tradition focusing on transient lateralized changes of electrocortical activity in the prefrontal cortex using electroencephalography (EEG). Lateral shifts of EEG alpha asymmetry in response to an aversive film consisting of scenes of real injury and death were assessed in healthy participants (n = 165). To evaluate the specificity of the 5-HTTLPR effect, participants were also tested for the COMT Val158Met polymorphism which is linked to dopamine inactivation. While viewing the film, individuals homozygous for the 5-HTTLPR short allele displayed a clear lateral shift of dorsolateral frontal activity to the right, which was virtually absent in participants carrying the long allele. The heightened electrocortical response to the aversive stimulation and its direction indicates a greater propensity of s/s homozygotes to experience withdrawal oriented affect in response to negative emotion cues in the environment. Moreover, together with previous research the findings support the notion of a link between the serotonergic system and self-regulation related to avoidance motivation, and a link between the dopaminergic system and self-regulation related to approach motivation.

Are there reciprocal relationships between substance use risk personality profiles and alcohol or tobacco use in early adolescence?

AIM

We examined whether reciprocal relationships were present between the SURPS personality profiles and substance use in early adolescence.

METHODS

Longitudinal data of four-waves of a broader effectiveness study were used from 1068 early adolescents.

RESULTS

Our cross-lagged models indicated that sensation seeking and impulsivity show strongest reciprocal associations with substance use during early adolescence. In contrast, no reciprocity was present between substance use and anxiety sensitivity and only one reciprocal relationship was present between substance use and hopelessness.

CONCLUSIONS

In trying to prevent early adolescents from alcohol and tobacco use, it might be of key importance to acknowledge the mutual influence between certain personality profiles and substance use. Specifically, sensation seeking and impulsivity are relevant during early adolescence and awareness of early adolescents' vulnerability for these personality predispositions is warranted.

The neurobiological correlates of childhood adversity and implications for treatment

OBJECTIVE

This article provides an overview of research on the neurobiological correlates of childhood adversity and a selective review of treatment implications.

METHOD

Findings from a broad array of human and animal studies of early adversity were reviewed.

RESULTS

Topics reviewed include neuroendocrine, neurotrophic, neuroimaging, and cognitive effects of adversity, as well as genetic and epigenetic influences. Effects of early-life stress on treatment outcome are considered, and development of treatments designed to address the neurobiological abnormalities is discussed.

CONCLUSION

Early adversity is associated with abnormalities of several neurobiological systems that are implicated in the development of psychopathology and other medical conditions. Early-life stress negatively impacts treatment outcome, and individuals may require treatments that are specific to this condition.

Association between Neurocognitive Impairment and the Short Allele of the 5-HTT Promoter Polymorphism in Depression: A Pilot Study

Depression has been shown to be associated with cognitive deficits in various cognitive domains. However, it is still unclear which factors contribute to cognitive impairment. The objective of this study was to find out whether a functional polymorphism in the promoter region of the serotonin transporter (5-HTTLPR) gene is associated with the impairment of cognitive functioning among depressed patients. In a pilot study, a sample of 19 patients with major depressive disorder (MDD) and 19 healthy controls was investigated with an extensive psychiatric and neuropsychological examination. All participants were genotyped for 5-HTTLPR. Depressed patients with the short allele of the 5-HTT promoter region exhibited inferior cognitive performance compared to patients with the long allele polymorphism. In healthy controls, no association between genotype and cognitive performance was found. The result suggests that in MDD patients with the short allele of the 5-HTTLPR polymorphism the vulnerability to cognitive impairment is increased compared to MDD patients without the short allele inheritance. These preliminary findings need to be confirmed in a larger cohort of MDD patients.

Who is predisposed to insomnia: a review of familial aggregation, stress-reactivity, personality and coping style

Insomnia is a common health complaint world-wide. Insomnia is a risk factor in the development of other psychological and physiological disorders. Therefore understanding the mechanisms which predispose an individual to developing insomnia has great transdiagnostic value. However, whilst it is largely accepted that a vulnerable phenotype exists there is a lack of research which aims to systematically assess the make-up of this phenotype. This review outlines the research to-date, considering familial aggregation and the genetics and psychology of stress-reactivity. A model will be presented in which negative affect (neuroticism) and genetics (5HTTLPR) are argued to lead to disrupted sleep via an increase in stress-reactivity, and further that the interaction of these variables leads to an increase in learned negative associations, which further increase the likelihood of poor sleep and the development of insomnia.

Identifying genetic predictors of depression risk: 5-HTTLPR and BDNF Val66Met polymorphisms are associated with rumination and co-rumination in adolescents

BACKGROUND

Despite research supporting moderate heritability of depression, efforts to replicate candidate gene associations to depression have yielded inconsistent results. We tested whether Val66Met and 5-HTTLPR exhibit utility as genetic markers of depression risk, testing for replicable associations to cognitive and interpersonal endophenotypes of depression (rumination and co-rumination), and further exploring developmental and sex moderation.

METHOD

In Study I, 228 youth (ages 8-14) of mothers with or without a history of MDD during the child's lifetime were recruited from the community. Replication tests were carried out in Study II, a sample of 87 youth with similar recruitment.

RESULTS

In Study I, the Val66Met single-nucleotide polymorphism (SNP) was associated with rumination in adolescents, but not children, such that adolescents homozygous for the Val allele reported higher rumination levels. Further, a cumulative genetic score (CGS) (Val66Val and 5-HTTLPR) predicted higher levels of co-rumination, specifically among adolescent girls. Both genetic associations maintained significance after covarying for current depressive symptomology, and the other endophenotype. Finally, both genetic associations exhibited similar effect sizes in Study II, although results did not reach statistical significance.

CONCLUSIONS

RESULTS replicate a previously reported association between the brain derived neurotrophic factor (BDNF) Val allele and rumination in adolescents, and provide preliminary support for a CGS predictive of co-rumination in adolescent girls. The current study indicates that candidate genes may demonstrate utility as consistent genetic markers of depression risk when focused on specific phenotypes, and supports the need to explore potential differential effects of developmental stage and sex. However, given the small sample sizes and possibility of chance findings, these results should be interpreted with caution pending replication.

Protocol for a collaborative meta-analysis of 5-HTTLPR, stress, and depression

BACKGROUND

Debate is ongoing about what role, if any, variation in the serotonin transporter linked polymorphic region (5-HTTLPR) plays in depression. Some studies report an interaction between 5-HTTLPR variation and stressful life events affecting the risk for depression, others report a main effect of 5-HTTLPR variation on depression, while others find no evidence for either a main or interaction effect. Meta-analyses of multiple studies have also reached differing conclusions.

METHODS/DESIGN

To improve understanding of the combined roles of 5-HTTLPR variation and stress in the development of depression, we are conducting a meta-analysis of multiple independent datasets. This coordinated approach utilizes new analyses performed with centrally-developed, standardized scripts. This publication documents the protocol for this collaborative, consortium-based meta-analysis of 5-HTTLPR variation, stress, and depression.

STUDY ELIGIBILITY CRITERIA

Our goal is to invite all datasets, published or unpublished, with 5-HTTLPR genotype and assessments of stress and depression for at least 300 subjects. This inclusive approach is to minimize potential impact from publication bias.

DATA SOURCES

This project currently includes investigators from 35 independent groups, providing data on at least N = 33,761 participants.The analytic plan was determined prior to starting data analysis. Analyses of individual study datasets will be performed by the investigators who collected the data using centrally-developed standardized analysis scripts to ensure a consistent analytical approach across sites. The consortium as a group will review and interpret the meta-analysis results.

DISCUSSION

Variation in 5-HTTLPR is hypothesized to moderate the response to stress on depression. To test specific hypotheses about the role of 5-HTTLPR variation on depression, we will perform coordinated meta-analyses of de novo results obtained from all available data, using variables and analyses determined a priori. Primary analyses, based on the original 2003 report by Caspi and colleagues of a GxE interaction will be supplemented by secondary analyses to help interpret and clarify issues ranging from the mechanism of effect to heterogeneity among the contributing studies. Publication of this protocol serves to protect this project from biased reporting and to improve the ability of readers to interpret the results of this specific meta-analysis upon its completion.

Polymorphism in serotonin receptor 3B is associated with pain catastrophizing

Pain catastrophizing, a coping style characterized by excessively negative thoughts and emotions in relation to pain, is one of the psychological factors that most markedly predicts variability in the perception of pain; however, only little is known about the underlying neurobiology. The aim of this study was to test for associations between psychological variables, such as pain catastrophizing, anxiety and depression, and selected polymorphisms in genes related to monoaminergic neurotransmission, in particular serotonin pathway genes. Three hundred seventy-nine healthy participants completed a set of psychological questionnaires: the Pain Catastrophizing Scale (PCS), the State-Trait Anxiety Inventory and Beck’s Depression Inventory, and were genotyped for 15 single nucleotide polymorphisms (SNPs) in nine genes. The SNP rs1176744 located in the serotonin receptor 3_B gene (5-HTR3B) was found to be associated with pain catastrophizing scores: both the global score and the subscales of magnification and helplessness. This is the first study to show an association between 5-HTR3B and PCS scores, thus suggesting a role of the serotonin pathway in pain catastrophizing. Since 5-HTR3B has previously been associated with descending pain modulation pathways, future studies will be of great interest to elucidate the molecular pathways involved in the relation between serotonin, its receptors and pain catastrophizing.

Relational interventions for child maltreatment: past, present, and future perspectives

It is well established that child maltreatment has significant deleterious effects for the individual as well as for society. We briefly review research regarding the impact of child maltreatment on the attachment relationship, highlighting the need for relational interventions for maltreated children and their families to effectively thwart negative developmental cascades that are so often observed in the context of child maltreatment. Next, historical and contemporaneous perspectives on relational interventions for individuals with histories of child maltreatment are discussed, with attention to the empirical evidence for and the current evidence-based status of several relationally based interventions for child maltreatment. Differential sensitivity to the environment is then discussed as a theoretical framework with important implications for interventions for individuals who have been reared in maltreating environments. Current research on neurobiology and maltreatment is then reviewed, with an emphasis on the need for future investigations on genetic variants, epigenetics, and the efficacy of relational interventions for maltreated children. We conclude with a discussion of the tenets of developmental psychopathology, their implications for relational interventions for child maltreatment, and recommendations for advancing the development, provision, and evaluation of relational interventions for individuals with histories of child maltreatment.

Working conditions, serotonin transporter gene polymorphism (5-HTTLPR) and anxiety disorders: a prospective cohort study

BACKGROUND

The etiology and pathology of anxiety disorders involve both genetic and environmental influences. Adverse working conditions may contribute to the development of anxiety. The serotonin transporter-linked polymorphic region (5-HTTLPR) has been implicated in stress sensitivity. Therefore, we investigated the potential interplay between 5-HTTLPR and job-related risk factors in the prediction of the occurrence of anxiety.

METHODS

We conducted a prospective study using the first two waves of a Swedish population-based cohort. At Wave I, 1585 individuals without anxiety, depression or dysthymia who were active in the labor market during both waves were included. Information on job demands, skill discretion, decision authority and social climate was collected at Wave I. After a three year interval, the presence of anxiety disorders was determined at Wave II. All 1585 participants were genotyped for 5-HTTLPR. Both additive and multiplicative models were considered in examining the potential interaction between 5-HTTLPR and adverse working conditions on the development of anxiety.

RESULTS

Anxiety was associated with high job demands but not with 5-HTTLPR. An interaction was observed between 5-HTTLPR and high job demands among females. Individuals with 5-HTTLPR high expression genotype (LL) developed anxiety disorders more frequently when exposed to high job demands compared to 'LS/SS' carriers.

LIMITATIONS

A limited number of participants developed anxiety.

CONCLUSIONS

High job demands predict the development of anxiety. The 5-HTT polymorphism has a moderating effect on the relationship between high job demands and anxiety among females.

Evaluation of heritable determinants of blood and brain serotonin homeostasis using recombinant inbred mice

The biogenic amine serotonin (5-HT, 5-hydroxytryptamine) exerts powerful, modulatory control over multiple physiological functions in the brain and periphery, ranging from mood and appetite to vasoconstriction and gastrointestinal motility. In order to gain insight into shared and distinct molecular and phenotypic networks linked to variations in 5-HT homeostasis, we capitalized on the stable genetic variation present in recombinant inbred mouse strains. This family of strains, all derived from crosses between C57BL/6J and DBA/2J (BXD) parents, represents a unique, community resource with approximately 40 years of assembled phenotype data that can be exploited to explore and test causal relationships in silico. We determined levels of 5-HT and 5-hydroxyindoleacetic acid from whole blood, midbrain and thalamus/hypothalamus (diencephalon) of 38 BXD lines and both sexes. All 5-HT measures proved highly heritable in each region, although both gender and region significantly impacted between-strain correlations. Our studies identified both expected and novel biochemical, anatomical and behavioral phenotypes linked to 5-HT traits, as well as distinct quantitative trait loci. Analyses of these loci nominate a group of genes likely to contribute to gender- and region-specific capacities for 5-HT signaling. Analysis of midbrain mRNA variations across strains revealed overlapping gene expression networks linked to 5-HT synthesis and metabolism. Altogether, our studies provide a rich profile of genomic, molecular and phenotypic networks that can be queried for novel relationships contributing risk for disorders linked to perturbed 5-HT signaling.

Interaction between the 5-HTTLPR genotype, impact of stressful life events, and trait neuroticism on depressive symptoms in healthy volunteers

INTRODUCTION

Recent biopsychological research on stress-related psychopathology shows promising evidence for the 5-hydroxytryptamine (5-HT) transporter linked polymorphic region (5-HTTLPR) genotype by life event interaction on depression. Yet, there appears to be variability in replicating such findings. From leading cognitive models of depression, it can be deduced that mainly high-impact events, particularly in stress-vulnerable, high trait neuroticism individuals who possess low coping abilities, can cause depression.

OBJECTIVE

The current study therefore examines the interaction between the 5-HTTLPR genotype, impact of life events, and trait neuroticism on depression symptoms.

PARTICIPANTS AND METHODS

A group of 771 healthy individuals, 595 women and 176 men aged 21.0±2.1 years, were genotyped for the 5-HTTLPR polymorphism and were rated for depressive symptoms, impact of life events, and neuroticism.

RESULTS

Only the low-allele expressing (S) 5-HTTLPR carriers showed vulnerability to depression exclusively when they also reported exposure to high-impact events and showed high neuroticism.

CONCLUSION

This suggests that cognitive vulnerabilities may mediate the 5-HTTLPR genotype by life event interaction on depression.

The 5-HTTLPR polymorphism in the serotonin transporter gene moderates the association between emotional behavior and changes in marital satisfaction over time

Why do some individuals become dissatisfied with their marriages when levels of negative emotion are high and levels of positive emotions are low, whereas others remain unaffected? Using data from a 13-year longitudinal study of middle-aged and older adults in long-term marriages, we examined whether the 5-HTTLPR polymorphism in the serotonin transporter gene moderates the association between negative and positive emotional behavior (objectively measured during marital conflict) and changes in marital satisfaction over time. For individuals with two short alleles of 5-HTTLPR, higher negative and lower positive emotional behavior at Time 1 predicted declines in marital satisfaction over time (even after controlling for depression and other covariates). For individuals with one or two long alleles, emotional behavior did not predict changes in marital satisfaction. We also found evidence for a crossover interaction (individuals with two short alleles of 5-HTTLPR and low levels of negative or high levels of positive emotion had the highest levels of marital satisfaction). These findings provide the first evidence of a specific genetic polymorphism that moderates the association between emotional behavior and changes in marital satisfaction over time and are consistent with increasing evidence that the short allele of this polymorphism serves as a susceptibility factor that amplifies sensitivity to both negative and positive emotional influences.

The Serotonin Link between Alcohol Use and Affective Disorders

Serotonin is imperative for the normal operations in the central nervous system. The serotonergic circuitry is implicated in many neuronal processes, and, especially so in mechanisms of emotional regulation and reward. Although function in the serotonergic circuitry has been shown to be abnormal in many pathological states like depression, anxiety, and addiction, its ubiquitous nature complicates efforts to pinpoint the exact loci of pathology. This becomes especially relevant when these conditions occur together, which they do frequently. In this review, we examine the literature on the role of serotonin in depression, anxiety, and addiction, identifying commonalities between these disorders to elucidate the mechanisms at work when they are comorbid. Specifically, we examine the role of serotonergic receptors, transporters, and networks in incidences of alcohol dependence that is comorbid with depression to facilitate a deeper understanding of these mechanisms necessary for the development of more effective and personalized treatments.

Childhood maltreatment and psychopathology: A case for ecophenotypic variants as clinically and neurobiologically distinct subtypes

OBJECTIVE

Childhood maltreatment increases risk for psychopathology. For some highly prevalent disorders (major depression, substance abuse, anxiety disorders, and posttraumatic stress disorder) a substantial subset of individuals have a history of maltreatment and a substantial subset do not. The authors examined the evidence to assess whether those with a history of maltreatment represent a clinically and biologically distinct subtype.

METHOD

The authors reviewed the literature on maltreatment as a risk factor for these disorders and on the clinical differences between individuals with and without a history of maltreatment who share the same diagnoses. Neurobiological findings in maltreated individuals were reviewed and compared with findings reported for these disorders.

RESULTS

Maltreated individuals with depressive, anxiety, and substance use disorders have an earlier age at onset, greater symptom severity, more comorbidity, a greater risk for suicide, and poorer treatment response than nonmaltreated individuals with the same diagnoses. Imaging findings associated with these disorders, such as reduced hippocampal volume and amygdala hyperreactivity, are more consistently observed in maltreated individuals and may represent a maltreatment-related risk factor. Maltreated individuals also differ from others as a result of epigenetic modifications and genetic polymorphisms that interact with experience to increase risk for psychopathology.

CONCLUSIONS

Phenotypic expression of psychopathology may be strongly influenced by exposure to maltreatment, leading to a constellation of ecophenotypes. While these ecophenotypes fit within conventional diagnostic boundaries, they likely represent distinct subtypes. Recognition of this distinction may be essential in determining the biological bases of these disorders. Treatment guidelines and algorithms may be enhanced if maltreated and nonmaltreated individuals with the same diagnostic labels are differentiated.

Defining the environment in gene-environment research: lessons from social epidemiology

In this article, we make the case that social epidemiology provides a useful framework to define the environment within gene-environment (G × E) research. We describe the environment in a multilevel, multidomain, longitudinal framework that accounts for upstream processes influencing health outcomes. We then illustrate the utility of this approach by describing how intermediate levels of social organization, such as neighborhoods or schools, are key environmental components of G × E research. We discuss different models of G × E research and encourage public health researchers to consider the value of including genetic information from their study participants. We also encourage researchers interested in G × E interplay to consider the merits of the social epidemiology model when defining the environment.

The challenge of causal inference in gene-environment interaction research: leveraging research designs from the social sciences

The integration of genetics and the social sciences will lead to a more complex understanding of the articulation between social and biological processes, although the empirical difficulties inherent in this integration are large. One key challenge is the implications of moving "outside the lab" and away from the experimental tools available for research with model organisms. Social science research methods used to examine human behavior in nonexperimental, real-world settings to date have not been fully taken advantage of during this disciplinary integration, especially in the form of gene-environment interaction research. This article outlines and provides examples of several prominent research designs that should be used in gene-environment research and highlights a key benefit to geneticists of working with social scientists.

The interacting effect of the BDNF Val66Met polymorphism and stressful life events on adolescent depression is not an artifact of gene-environment correlation: evidence from a longitudinal twin study

BACKGROUND

Confounding introduced by gene-environment correlation (rGE) may prevent one from observing a true gene-environment interaction (G × E) effect on psychopathology. The present study investigated the interacting effect of the BDNF Val66Met polymorphism and stressful life events (SLEs) on adolescent depression while controlling for the rGE by two means: separating pure environmental factors (independent SLEs) from the environmental factors under partial genetic control (dependent SLEs) and adopting a prospective longitudinal design.

METHODS

A total of 780 pairs of Chinese twins, aged 11-17 years (mean = 13.6, SD = 1.8) at intake, were followed up twice. Self-reported depression symptoms at Time 1 and Time 2 were assessed by the Children's Depression Inventory (CDI). SLEs occurring between Time 1 and Time 2 were assessed by a self-reported checklist. SLEs were differentiated into independent and dependent ones and were validated by heritability analyses using twin design. The interacting effects between the BDNF Val66Met polymorphism and numbers of SLEs (total SLEs and independent SLEs) on intraindividual change of depression symptoms were examined.

RESULTS

After controlling for sex, age, age square, and Time 1 depression, both total SLEs × BDNF Val66Met genotype and independent SLEs × BDNF Val66Met genotype significantly predicted Time 2 depression. Val allele carriers (Val/Val and Val/Met) were more susceptible to the detrimental effects of stress.

CONCLUSIONS

There is a true G × E effect underlying the observed interaction between BDNF Val66Met polymorphism and environmental stress on depression.

Effects of citalopram and escitalopram on fMRI response to affective stimuli in healthy volunteers selected by serotonin transporter genotype

This study was designed to assess whether functional magnetic resonance imaging (fMRI) following antidepressant administration (pharmaco-fMRI) is sufficiently sensitive to detect differences in patterns of activation between enantiomers of the same compound. Healthy adult males (n=11) participated in a randomized, double-blind, cross-over trial with three medication periods during which they received citalopram (racemic mixture), escitalopram (S-citalopram alone), or placebo for 2 weeks. All participants had high expression serotonin transporter genotypes. An fMRI scan that included passive viewing of overt and covert affective faces and affective words was performed after each medication period. Activation in response to overt faces was greater following escitalopram than following citalopram in the right insula, thalamus, and putamen when the faces were compared with a fixation stimulus. For the rapid covert presentation, a greater response was observed in the left middle temporal gyrus in the happy versus fearful contrast following escitalopram than following citalopram. Thus, the combination of genomics and fMRI was successful in discriminating between two very similar drugs. However, the pattern of activation observed suggests that further studies are indicated to understand how to optimally combine the two techniques.

HTR2A gene-child abuse interaction and association with a history of suicide attempt among Caucasian depressed psychiatric inpatients

BACKGROUND

The serotonin transporter gene polymorphism (5HTTLPR) has been associated with vulnerability for depression after exposure to stressful life event as well as with difference in treatment response to SSRI. Although the A/A genotype of the serotonin receptor SNP (rs7997012) was associated with better citalopram response than the G/G in the STAR⁎D sample, the effects of this SNP in the moderation of child abuse history on the characteristics of mental illnesses are not well understood. We examined if there are similar gene-environment interaction with the SNP.

METHODS

Retrospective chart review of 250 Caucasian depressed psychiatric inpatients, who had genotype for rs7997012. Subjects with each genotype were subcategorized into 2 groups with/without history of child abuse. The history of suicide attempts of each group was compared.

RESULTS

A trend for an interaction was found between the HTR2A genotype and child abuse history influencing the prevalence of suicide attempts. Although each genotype did not show significant difference in the risk of suicide attempt when there was no abuse history, the A carriers (A/A+A/G) showed significantly higher rate of suicide attempt compared to the G/G when there is a history of child abuse (48.4% versus 22.7% respectively, p=0.0050). The likelihood ratio test from the logistic model showed a trend for an interaction between the A/A genotype and abuse history (Odds Ratio 2.10, χ(2)=2.49, p=0.11).

LIMITATIONS

Retrospective study design and small sample size with borderline significance.

CONCLUSIONS

Our findings showed a potential interaction between the HTR2A gene and stressful life events.

Altered inflammatory responsiveness in serotonin transporter mutant rats

Background

Growing evidence suggests that alterations of the inflammatory/immune system contribute to the pathogenesis of depression. Indeed, depressed patients exhibit increased levels of inflammatory markers in both the periphery and the brain, and high comorbidity exists between major depression and diseases associated with inflammatory alterations. In order to characterize the link between depression and inflammation, we aimed to investigate whether an altered inflammatory system is present in a genetic model of vulnerability for depression, namely rats with partial or total deletion of the serotonin transporter (SERT) gene.

Methods

Wild-type, heterozygous and homozygous SERT rats were analyzed under basal condition or following a challenge with an acute injection of lipopolysaccharide (LPS) and killed 24 h or 5 days later.

Results

We found that SERT mutant rats show altered cytokine expression in the dorsal and ventral hippocampus at basal conditions, and they also display an exacerbated cytokine response to the LPS challenge. Moreover, mutant rats exhibit differences in the expression of markers for microglia activation.

Conclusion

Based on these data, we suggest that basal or functional alterations of immune/inflammatory systems might contribute to the phenotype of SERT rats and to their heightened susceptibility to depressive-like behavior.

Negative life events and corticotropin-releasing-hormone receptor1 gene in recurrent major depressive disorder

Major depressive disorder (MDD) is a long-term, recurrent condition that often takes a chronic course. It seems imperative that research should be focused on gaining a better understanding of what predicts recurrent MDD. As a major mediator of the stress response, corticotropin-releasing-hormone receptor 1 (CRHR1) has been demonstrated to be an important contributor to the pathogenesis of MDD. In this study, we show a significant increase in the G-allele (rs242939) of the CRHR1 gene in the recurrent MDD group compared with the control group, and an overrepresentation of G-G-T hyplotype of the CRHR1 gene in recurrent MDD. We also demonstrate the interaction of the CRHR1 gene and negative life events in recurrent MDD. These results suggest that the CRHR1 gene could modify the susceptibility to developing recurrent MDD following negative life events in adulthood.

Childhood emotional environment and self-injurious behaviors: the moderating role of the BDNF Val66Met polymorphism

BACKGROUND

Previous theory has suggested that invalidating environments in the form of emotional maltreatment should be a specific risk factor for the development of self-injurious behaviors (Linehan, 1993, Cognitive-Behavioral Treatment of Borderline Personality Disorder, New York, Guilford Press). However, results from previous studies have been mixed, possibly indicating that this effect may not be the same for all individuals. In fact, some individuals may be more susceptible to environmental influences (i.e., phenotypic plasticity), and this susceptibility may be in part a function of genes that are involved in neuroplasticity (e.g., the brain-derived neurotrophic factor [BDNF] Val66Met polymorphism).

METHOD

We explored the interaction between retrospective reports of childhood emotional environment and the BDNF Val66Met polymorphism in relation to a history of two main types of self-injurious behaviors, suicide attempt and nonsuicidal self-injury (NSSI), in a sample of individuals with a history of involvement in the criminal justice system.

RESULTS

For individuals with two Val alleles, there was a significant direct relationship between emotional maltreatment and self-injurious behaviors. However, the relationship was not significant for Met carriers.

LIMITATIONS

The data are cross-sectional, which means causal inferences cannot be drawn.

CONCLUSIONS

The results indicate the possibility of a common etiological pathway for NSSI and suicide attempts.

Genotyping serotonin transporter polymorphisms 5-HTTLPR and rs25531 in European- and African-American subjects from the National Institute of Mental Health's Collaborative Center for Genomic Studies

A number of studies have suggested DNA sequence variability in the serotonin transporter gene (SLC6A4) between European-American (EA) and African-American (AA) populations, which could be clinically important, given the central role SLC6A4 has in serotonin transmission. However, these studies have had relatively small samples, used self-reported measures of race, and have only tested the promoter-linked polymorphism 5-HTTLPR. Here we genotype 5-HTTLPR and rs25531, a neighboring functional polymorphism, in 954 AA and 2622EA subjects from a National Institute of Mental Health repository sample. Genotyping was performed using fragment analysis by capillary electrophoresis. AA, as compared with EA, groups had lower frequencies of the S allele (0.25 vs 0.43) and SS genotype (0.06 vs 0.19) at 5-HTTLPR, and higher rates of the G allele at rs25531 (0.21 vs 0.075). A rare xL variant at 5-HTTLPR was also more common among AAs (0.017 vs 0.008). When the polymorphisms were redefined into a high- and low-transcription haplotypes, the AA group showed significantly fewer low-transcription variants (χ(2)=4.8, P=0.03). No genotypes were associated with major depression, any anxiety disorder, or neuroticism in either EA or AA populations. This is the largest study to show SLC6A4 genotype differences between EA and AA populations, and the first to include rs25531. Lack of associations with clinical outcomes may reflect untested moderating environmental influences.

The role of inflammatory cytokines on the aetiopathogenesis of depression

OBJECTIVE

The primary focus of this review is to provide an overview of the role of inflammation in the development of depression. The article will describe how inflammatory cytokines contribute to depression via action on three major pathways in the brain: the neuroendocrine; neurotransmitter depletion; and neuroprogression pathways.

METHODS

An online literature search was carried out in July 2012. Original articles and reviews were selected if they discussed the role of inflammation on the development of depression.

RESULTS

There is a large body of current research on the role of inflammatory cytokines on the development of depression. Cytokines have been found to interact with different pathways in the brain, and may contribute to the development of depression. Cytokines cause hypercortisolaemia by dysregulation of the hypothalamic-pituitary-adrenal axis directly by activating it and indirectly by modifying glucocorticoid receptor sensitivity to cortisol leading to cortisol hypersecretion. Cytokines deplete central synaptic serotonin levels by reducing its synthesis and increasing its reuptake. They may also deplete neurotrophic factors which are believed to play a neuroprotective role against depression. Cytokines activate cellular cascades that cause excitotoxicity and apoptosis and inhibit neurogenesis in the hippocampus.

CONCLUSION

There is a growing body of correlative studies that suggest inflammatory cytokines may be a central factor that can affect multiple neuronal pathways and have an additive effect on the development of depression. However, the fact that not all people with inflammatory conditions suffer from depression suggests that depression is not purely a result of elevated inflammatory cytokines. Depression may be a result of a complex pathology that remains an area of growing interest and importance.

The serotonin transporter gene-linked polymorphic region (5-HTTLPR) and cortisol stress reactivity: a meta-analysis

Recent meta-analyses have stimulated an active debate on whether the serotonin transporter gene-linked polymorphic region (5-HTTLPR) is associated with an elevated vulnerability to psychiatric diseases upon exposure to environmental adversity. As a potential mechanism explaining genotype-dependent differences in stress sensitivity, altered stress-induced activation of the hypothalamus-pituitary-adrenal (HPA) axis has been investigated in several experimental studies, with most of these studies comprising small samples. We evaluated the association of 5-HTTLPR genotype and cortisol reactivity to acute psychosocial stress by applying a meta-analytical technique based on eleven relevant data sets (total N=1686), which were identified through a systematic literature search up to October 2011. This meta-analysis indicates a small (d=0.27), but significant association between 5-HTTLPR genotype and HPA-axis reactivity to acute psychosocial stress with homozygous carriers of the S allele displaying increased cortisol reactivity compared with individuals with the S/L and L/L genotype. The latter association was not further moderated by participants' age, sex or the type of stressor. Formal testing revealed no evidence for a substantial selection or publication bias. Our meta-analytical results are consistent with a wide variety of experimental studies indicating a significant association between 5-HTTLPR genotype and intermediate phenotypes related to stress sensitivity. Future studies are needed to clarify the consistency of this effect and to further explore whether altered HPA-axis stress reactivity reflects a potential biological mechanism conveying an elevated risk for the development of stress-related disorders in S allele carriers.

Refining the Candidate Environment: Interpersonal Stress, the Serotonin Transporter Polymorphism, and Gene-Environment Interactions in Major Depression

Meta-analytic evidence supports a gene-environment (G×E) interaction between life stress and the serotonin transporter polymorphism (5-HTTLPR) on depression, but few studies have examined factors that influence detection of this effect, despite years of inconsistent results. We propose that the "candidate environment" (akin to a candidate gene) is key. Theory and evidence implicate major stressful life events (SLEs)-particularly major interpersonal SLEs-as well as chronic family stress. Participants (N = 400) from the Youth Emotion Project (which began with 627 high school juniors oversampled for high neuroticism) completed up to five annual diagnostic and life stress interviews and provided DNA samples. A significant G×E effect for major SLEs and S-carrier genotype was accounted for significantly by major interpersonal SLEs but not significantly by major non-interpersonal SLEs. S-carrier genotype and chronic family stress also significantly interacted. Identifying such candidate environments may facilitate future G×E research in depression and psychopathology more broadly.

Acute responsivity of the serotonergic system to S-citalopram and positive emotionality-the moderating role of the 5-HTTLPR

According to the idea that the central serotonergic system has a modulatory function on behavior and personality in general, we aimed to highlight its association to habitual positive emotionality. In a placebo-controlled double-blind and randomized cross-over neuroendocrine challenge design (n = 72 healthy males) we investigated the association of the central serotonergic responsivity, 5-HTTLPR-genotype as well as their combined effects on positive emotionality. Regression analyses revealed an involvement of the serotonergic system in positive emotionality. There was, however, no direct association between positive emotionality and cortisol responses to S-citalopram; rather 5-HTTLPR-genotype showed an association (p < 0.05). That is, positive emotionality scores increased with the number of s-alleles carried by the individuals. Most notable was the moderating role of 5-HTTLPR-genotype (p < 0.05) on the association between acute serotonergic responsivity and positive emotionality. Indeed, this association was only found in ss-homozygotes, in which the acute responsivity of the serotonergic system additionally seems to contribute to the level of positive emotionality (r = 0.70, p < 0.05). The findings correspond to previous research demonstrating that the 5-HTTLPR is not only involved in the negative-emotional aspects of behavior and temperament, but is associated, moreover, with positive affectivity-supporting the assumption of its valence-neutrality. In addition, our data are in line with the idea of possible influences of the 5-HTTLPR-genotype on early neuronal development. They also indicate the need for further studies in order to clearly elucidate the role of the serotonergic system and its subcomponents in the regulation of positive emotionality.

Modulation of amygdala response and connectivity in depression by serotonin transporter polymorphism and diagnosis

BACKGROUND

Polymorphisms in the serotonin transporter gene (5-HTTLPR) modulate amygdala activity in healthy individuals. Increased responses to negative stimuli in carriers of low transcription alleles have been proposed to contribute to the pathogenesis of depression. We sought to investigate the effects of genotype as well as diagnosis in patients with depression.

METHODS

Subjects with recurrent depression (n=67) and matched healthy controls (n=49) participated in a fMRI task of implicit processing of sad facial stimuli. Effects of biallelic (short (S) and long (L) alleles) and triallelic (including rs25531 A/G single nucleotide variation) models of 5-HTTLPR polymorphisms on amygdala activity and connectivity were investigated.

RESULTS

Significant effects were observed of both genotype and diagnosis on amygdala activity. Increased amygdala activity was associated with 5-HTTLPR genotype in low transcription allele carriers as well as with a diagnosis of depression. The connectivity analysis revealed a main effect of genotype with reduced connectivity to the subgenual region of the anterior cingulate in carriers of the low transcription alleles. There was also a main effect of diagnosis with reduced connectivity to the dorsal region of the anterior cingulate and to the dorsolateral prefrontal cortex in depression. There were no interaction effects between genotype and diagnosis in amygdala activity or connectivity.

CONCLUSIONS

Significant independent effects of genotype and diagnosis on amygdala responsivity were revealed. The effects of genotype and diagnosis on amygdala connectivity showed a regional segregation, suggesting that 5-HTTLPR polymorphisms bias frontal-limbic connectivity while the development of depression involves more extensive neural disturbances. These findings point to the potential of connectivity maps as a diagnostic biomarker for depression.

Positron emission tomography quantification of serotonin transporter in suicide attempters with major depressive disorder

BACKGROUND

Several lines of evidence implicate abnormal serotonergic function in suicidal behavior and completed suicide, including low serotonin transporter binding in postmortem studies of completed suicide. We have also reported low in vivo serotonin transporter binding in major depressive disorder (MDD) during a major depressive episode using positron emission tomography (PET) with [(11)C]McN5652. We quantified regional brain serotonin transporter binding in vivo in depressed suicide attempters, depressed nonattempters, and healthy controls using PET and a superior radiotracer, [(11)C]DASB.

METHODS

Fifty-one subjects with DSM-IV current MDD, 15 of whom were past suicide attempters, and 32 healthy control subjects underwent PET scanning with [(11)C]DASB to quantify in vivo regional brain serotonin transporter binding. Metabolite-corrected arterial input functions and plasma free-fraction were acquired to improve quantification.

RESULTS

Depressed suicide attempters had lower serotonin transporter binding in midbrain compared with depressed nonattempters (p = .031) and control subjects (p = .0093). There was no difference in serotonin transporter binding comparing all depressed subjects with healthy control subjects considering six a priori regions of interest simultaneously (p = .41).

CONCLUSIONS

Low midbrain serotonin transporter binding appears to be related to the pathophysiology of suicidal behavior rather than of major depressive disorder. This is consistent with postmortem work showing low midbrain serotonin transporter binding capacity in depressed suicides and may partially explain discrepant in vivo findings quantifying serotonin transporter in depression. Future studies should investigate midbrain serotonin transporter binding as a predictor of suicidal behavior in MDD and determine the cause of low binding.

The use of cognitive bias modification and imagery in the understanding and treatment of depression

Cognitive models of depression form the natural link between neurobiological and social accounts of the illness. Interest in the role of cognition in depression has recently been stimulated by the advent of simple, computer-based "cognitive bias modification" (CBM) techniques which are able to experimentally alter cognitive habits in clinical and non-clinical populations. In this chapter, we review recent work which has used CBM techniques to address questions of aetiology and treatment in depression with a particular focus on the interface with neurobiological and social processes relevant to the illness. We find that there are early signs that CBM may be a useful tool in exploring the aetiology of depression, particularly in regard to the neural and genetic factors which influence susceptibility to the illness and response to treatment. There is also early evidence suggesting that CBM has promise in the treatment and prevention of depression. This work suggests that the beneficial effects of CBM are mediated by the interaction between cognitive functioning and environmental and social information. In summary, by providing a method for altering habitual cognitive function in experimental and clinical settings CBM techniques have begun to further the understanding of and the treatment for depression.

Reduced serotonin transporter availability decreases prefrontal control of the amygdala

After a threatening event, the risk of developing social psychopathologies is increased in short-allele (s) carriers of the serotonin transporter gene. The amygdala becomes overresponsive to emotional stimuli, an effect that could be driven by local hypersensitivity or by reduced prefrontal regulation. This study distinguishes between these two hypotheses by using dynamic causal modeling of fMRI data acquired in a preselected cohort of human s-carriers and homozygous long-allele carriers. Increased amygdala activity in s-carriers originates from reduced prefrontal inhibitory regulation when social emotional behavior needs to be controlled, suggesting a mechanism for increased vulnerability to psychopathologies.

Assessment of genetic and nongenetic interactions for the prediction of depressive symptomatology: an analysis of the Wisconsin Longitudinal Study using machine learning algorithms

OBJECTIVES

We examined depression within a multidimensional framework consisting of genetic, environmental, and sociobehavioral factors and, using machine learning algorithms, explored interactions among these factors that might better explain the etiology of depressive symptoms.

METHODS

We measured current depressive symptoms using the Center for Epidemiologic Studies Depression Scale (n = 6378 participants in the Wisconsin Longitudinal Study). Genetic factors were 78 single nucleotide polymorphisms (SNPs); environmental factors-13 stressful life events (SLEs), plus a composite proportion of SLEs index; and sociobehavioral factors-18 personality, intelligence, and other health or behavioral measures. We performed traditional SNP associations via logistic regression likelihood ratio testing and explored interactions with support vector machines and Bayesian networks.

RESULTS

After correction for multiple testing, we found no significant single genotypic associations with depressive symptoms. Machine learning algorithms showed no evidence of interactions. Naïve Bayes produced the best models in both subsets and included only environmental and sociobehavioral factors.

CONCLUSIONS

We found no single or interactive associations with genetic factors and depressive symptoms. Various environmental and sociobehavioral factors were more predictive of depressive symptoms, yet their impacts were independent of one another. A genome-wide analysis of genetic alterations using machine learning methodologies will provide a framework for identifying genetic-environmental-sociobehavioral interactions in depressive symptoms.

How genes and the social environment moderate each other

Recent research has suggested that the social environment can moderate the expression of genetic influences on health and that genetic influences can shape an individual's sensitivity to the social environment. Evidence supports 4 major mechanisms: genes can influence an individual's response to environmental stress, genes may enhance an individual's sensitivity to both favorable and adverse environments, inherited characteristics may better fit with some environments than with others, and inherited capabilities may only become manifest in challenging or responsive environments. Further progress depends on better recognition of patterns of gene-environment interaction, improved methods of assessing the environment and its impact on genetic mechanisms, the use of appropriately designed laboratory studies, identification of heritable differences in an individual before environmental moderation occurs, and clarification of the timing of the impact of social and genetic moderation.

Social, behavioral, and genetic linkages from adolescence into adulthood

The influence of genetic factors on health and behavior is conditioned by social, cultural, institutional, and physical environments in which individuals live, work, and play. We encourage studies supporting multilevel integrative approaches to understanding these contributions to health, and describe the Add Health study as an exemplar. Add Health is a large sample of US adolescents in grades 7 to 12 in 1994-1995 followed into adulthood with 4 in-home interviews and biomarker collections, including DNA. In addition to sampling multiple environments and measuring diverse social and health behavior, Add Health features a fully articulated behavioral genetic sample (3000 pairs) and ongoing genotyping of 12,000 archived samples. We illustrate approaches to understanding health through investigation of the interplay among biological, psychosocial, and physical, contextual, or cultural experiences.

Hippocampal volume and serotonin transporter polymorphism in major depressive disorder

OBJECTIVE

The main aim of the present study was to replicate a previous finding in major depressive disorder (MDD) of association between reduced hippocampal volume and the long variant of the di- and triallelic serotonin transporter polymorphism in SLC6A4 on chromosome 17q11.2. Secondarily, we also hypothesised that 5-HTTLPR may be a risk factor for MDD.

METHODS

Quantitative magnetic resonance imaging (MRI) of the hippocampus was studied in 23 inpatients suffering from MDD and in 33 healthy controls. Normalised volumetric MRI data of hippocampus were assessed with adjustment for total brain volume and tensor-based morphometry was used to elucidate structural brain differences. A triallelic genetic marker resulting from two SLC6A4 promoter region polymorphisms, 5-HTTLPR and rs25531, was analysed for association with MDD and quantitative traits.

RESULTS

Healthy controls had a smaller relative hippocampal volume (relative to brain size) but a larger total brain volume compared with patients with MDD. For patients compared with healthy controls, atrophy was found in the right temporal lobe and pons medulla. Allele and genotype frequencies were strikingly different from the previous study that we aimed to replicate, and no significant associations with the serotonin transporter polymorphism were found.

CONCLUSIONS

The present quantitative and morphometric MRI study was not able to replicate the previous finding of association between reduced hippocampal volume in depressed patients and the serotonin transporter polymorphism.

The role of gene-environment correlations and interactions in middle childhood depressive symptoms

Depression is known to be associated with a wide array of environmental factors. Such associations are due at least in part to genetic influences on both. This issue has been little explored with preadolescent children. Measures of family chaos and parenting style at age 9 and child depressive symptoms at age 12 were completed by 3,258 twin pairs from the Twins Early Development Study and their parents. Quantitative genetic modeling was used to explore common and unique genetic and environmental influences on both family environment and later depressive symptoms. Depressive symptoms at age 12 were significantly heritable. Moderate genetic effects influenced parenting style and family chaos at the age of 9, indicating gene-environment correlation. There were significant genetic correlations between family environment and depressive symptoms. There was some evidence of a Gene × Environment interaction, with stronger genetic effects on depressive symptoms for children with more suboptimal family environment. There was an Environment × Environment interaction, with effects of nonshared environment on depressive symptoms stronger for twins with more adverse parenting experiences. There is some evidence for gene-environment correlation between aspects of family environment in middle childhood and subsequent depressive symptoms. This suggests that one of the mechanisms by which genes lead to depressive symptoms may be by themselves influencing depressogenic environments.

Research review: the role of cytokines in depression in adolescents: a systematic review

BACKGROUND

While cytokines have been implicated in the pathophysiology of depression in adults, the potential role in younger age groups such as adolescents is less clear. This article therefore reviews the literature (a) to explore the relationship between cytokines and depression in adolescents, and (b) to examine how cytokines may be related to adolescent depression in the context of other neurobiological theories of depression.

METHOD

A systematic review of the scientific literature on the subject was conducted in February 2013, searching the Web of Knowledge, PubMed (Medline), PsycInfo and Cochrane electronic databases.

RESULTS

Eighteen studies were identified measuring both depression or depressive symptoms and cytokines or immune markers in adolescents. Adolescents with depression show age-specific characteristics of the immune and inflammatory system, specifically in NK cell activity and in pro-inflammatory cytokines (such as IL-1β and TNF-α). In addition, the role of cytokines in adolescent depression is influenced by neurodevelopment, hormonal changes, stress and trauma.

CONCLUSIONS

There may be differences in the neurobiology of adolescent major depressive disorder (MDD) compared with adult MDD. Increased understanding of the role of cytokines in adolescent MDD may lead to improved outcomes in the treatment of adolescent depression.

Multi-cultural association of the serotonin transporter gene (SLC6A4) with substance use disorder

A number of studies have reported associations between the serotonin transporter gene (SLC6A4) and alcohol, heroin, cocaine, or methamphetamine abuse. Other studies have yielded contrary results. There are a number of reasons for non-replication, including inadequate statistical power, population stratification, and poor phenotype definition. This study was to test the association using a meta-analytic approach across a variety of racial and ethnic populations. Using the genotype data of 55 studies (7999 cases, 8264 controls, and 676 families or parent-offspring trios) published in the past 15 years, we have conducted comprehensive meta-analyses to examine the associations of the 5-HTTLPR and STin2 polymorphisms with substance use disorder. The meta-analyses support the associations of 5-HTTLPR with alcohol, heroin, cocaine, and methamphetamine dependence and abuse (eg, the smallest P-values were 0.0058 with odds ratio (OR)=0.54 (0.35, 0.84); 0.0024 with OR=0.77 (0.66, 0.91); 0.018 with OR=1.38 (1.06, 1.81); and 0.028 with OR=0.46 (0.23, 0.92) for alcohol, heroin, cocaine, and methamphetamine dependence/abuse, respectively). When all the phenotypes are combined, the P-value was 0.0006 with OR=0.86 (0.78, 0.94) in the combined European, Asian, and Mexican populations and P-value was 0.0028 with OR=1.41 (1.13, 1.78) in the African populations. Evidence of significant associations was also identified in other subgroup analyses regarding differently combined substance and populations. The effect sizes of 5-HTTLPR were comparable among the European, Asian, and Mexican populations, however, the risk allele was more frequent in Asians than in Europeans and Mexicans. The opposite directions of risk allele in African population might be driven by the opposite directions of risk allele in cocaine dependence. This meta-analysis supports that the association of the SLC6A4 gene with substance use disorder varies depending on substances with different risk allele frequencies in the multi-cultural populations. Further studies using larger sample size are warranted.

Common and rare alleles of the serotonin transporter gene, SLC6A4, associated with Tourette's disorder

To evaluate the hypothesis that functionally over-expressing alleles of the serotonin transporter (SERT) gene (solute carrier family 6, member 4, SLC6A4) are present in Tourette's disorder (TD), just as we previously observed in obsessive compulsive disorder (OCD), we evaluated TD probands (N = 151) and controls (N = 858). We genotyped the refined SERT-linked polymorphic region 5-HTTLPR/rs25531 and the associated rs25532 variant in the SLC6A4 promoter plus the rare coding variant SERT isoleucine-to-valine at position 425 (I425V). The higher expressing 5-HTTLPR/rs25531 LA allele was more prevalent in TD probands than in controls (χ(2)  = 5.75; P = 0.017; odds ratio [OR], 1.35); and, in a secondary analysis, surprisingly, it was significantly more frequent in probands who had TD alone than in those who had TD plus OCD (Fisher's exact test; P = 0.0006; OR, 2.29). Likewise, the higher expressing LAC haplotype (5-HTTLPR/rs25531/rs25532) was more frequent in TD probands than in controls (P = 0.024; OR, 1.33) and also in the TD alone group versus the TD plus OCD group (P = 0.0013; OR, 2.14). Furthermore, the rare gain-of-function SERT I425V variant was observed in 3 male siblings with TD and/or OCD and in their father. Thus, the cumulative count of SERT I425V becomes 1.57% in OCD/TD spectrum conditions versus 0.15% in controls, with a recalculated, family-adjusted significance of χ(2) = 15.03 (P < 0.0001; OR, 9.0; total worldwide genotyped, 2914). This report provides a unique combination of common and rare variants in one gene in TD, all of which are associated with SERT gain of function. Thus, altered SERT activity represents a potential contributor to serotonergic abnormalities in TD. The present results call for replication in a similarly intensively evaluated sample. © 2013 Movement Disorder Society.

The interaction between child maltreatment, adult stressful life events and the 5-HTTLPR in major depression

Both childhood maltreatment and adult stressful life events are established risk factors for the onset of depression in adulthood. However, the interaction between them can be viewed through two conflicting frameworks. Under a mismatch hypothesis stressful childhoods allow 'adaptive programming' for a stressful adulthood and so can be protective. Only when childhood and adulthood do not match is there a risk of behavioural problems. Alternatively, under the cumulative stress hypothesis we expect increased risk with each additional stressor. It has also been suggested that an individual's genetic background may determine the extent they undergo adaptive programming, and so which of these two hypotheses is relevant. In this study we test for an interaction between exposure to childhood maltreatment and adult stressful life events in a retrospective sample of 455 individuals, using major depression as the outcome. We also test whether this interaction differs by genotype at the 5-HTTLPR, a candidate for an individual's plasticity to adaptive programming. Early maltreatment and stressful life events in adulthood interacted to produce increased risk for depression over each individually (p = 0.055). This supports the cumulative stress hypothesis over the mismatch hypothesis, at least with respect to severe environmental risk factors. This effect was not altered by 5-HTTLPR allele, suggesting there was no difference by genotype in adaptive programming to these events. We suggest that the apparent additional vulnerability to stressful events of those who have experienced maltreatment has clinical relevance, highlighting the importance of providing support beyond the immediate aftermath of maltreatment into adulthood.

Vulnerability to depression: a moderated mediation model of the roles of child maltreatment, peer victimization, and serotonin transporter linked polymorphic region genetic variation among children from low socioeconomic status backgrounds

Child maltreatment, peer victimization, and a polymorphism of the serotonin transporter gene (5-HTTLPR) were examined as predictors of depressive symptomatology. Children (M age = 11.26, SD = 1.65), including 156 maltreated and 145 nonmaltreated children from comparable low socioeconomic backgrounds, provided DNA samples and self-reports of relational peer victimization, overt peer victimization, and depressive symptoms. Path analysis showed that relational and overt victimization mediated the association between child maltreatment and depressive symptoms. Bootstrapping procedures were used to test moderated mediation and demonstrated that genotype moderated the indirect effects of relational and overt victimization on child depressive symptoms, such that victimized children with the long/long variation were at an increased risk for depressive symptoms compared to victimized children carrying a short allele. Results highlight the utility of examining process models that incorporate biological and psychological factors contributing to the development of depressive symptomatology and provide direction toward understanding and promoting resilience among high-risk youth from a multiple levels of analysis approach.