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

Imaging genetics paradigms in depression research: Systematic review and meta-analysis

Imaging genetics studies involving participants with major depressive disorder (MDD) have expanded. Nevertheless, findings have been inconsistent. Thus, we conducted a systematic review and meta-analysis of imaging genetics studies that enrolled MDD participants across major databases through June 30th, 2017. Sixty-five studies met eligibility criteria (N = 4034 MDD participants and 3293 controls), and there was substantial between-study variability in the methodological quality of included studies. However, few replicated findings emerged from this literature with only 22 studies providing data for meta-analyses (882 participants with MDD and 616 controls). Total hippocampal volumes did not significantly vary in MDD participants or controls carrying either the BDNF Val66Met 'Met' (386 participants with MDD and 376 controls) or the 5-HTTLPR short 'S' (310 participants with MDD and 230 controls) risk alleles compared to non-carriers. Heterogeneity across studies was explored through meta-regression and subgroup analyses. Gender distribution, the use of medications, segmentation methods used to measure the hippocampus, and age emerged as potential sources of heterogeneity across studies that assessed the association of 5-HTTLPR short 'S' alleles and hippocampal volumes. Our data also suggest that the methodological quality of included studies, publication year, and the inclusion of brain volume as a covariate contributed to the heterogeneity of studies that assessed the association of the BDNF Val66Met 'Met' risk allele and hippocampal volumes. In exploratory voxel-wise meta-analyses, MDD participants carrying the 5-HTTLPR short 'S' allele had white matter microstructural abnormalities predominantly in the corpus callosum, while carriers of the BDNF Val66Met 'Met' allele had larger gray matter volumes and hyperactivation of the right middle frontal gyrus compared to non-carriers. In conclusion, few replicated findings emerged from imaging genetics studies that included participants with MDD. Nevertheless, we explored and identified specific sources of heterogeneity across studies, which could provide insights to enhance the reproducibility of this emerging field.

Prenatal Stress, Maternal Immune Dysregulation, and Their Association With Autism Spectrum Disorders

PURPOSE OF REVIEW

While genetic factors are a major etiological contributor to autism spectrum disorder (ASD), evidence also supports a role for environmental factors. Herein, we will discuss two such factors that have been associated with a significant proportion of ASD risk: prenatal stress exposure and maternal immune dysregulation, and how sex and gender relate to these factors.

RECENT FINDINGS

Recent evidence suggests that maternal stress susceptibility interacts with prenatal stress exposure to affect offspring neurodevelopment. Additionally, understanding of the impact of maternal immune dysfunction on ASD has recently been advanced by recognition of specific fetal brain proteins targeted by maternal autoantibodies, and identification of unique mid-gestational maternal immune profiles. Animal models have been developed to explore pathophysiology targeting both of these factors, with limited sex-specific effects observed. While prenatal stress and maternal immune dysregulation are associated with ASD, most cases of these prenatal exposures do not result in ASD, suggesting interaction with multiple other risks. We are beginning to understand the behavioral, pharmacopathological, and epigenetic effects related to these interactions, as well as potential mitigating factors. Sex differences of these risks have been understudied but are crucial for understanding the higher prevalence of ASD in boys. Continued growth in understanding of these mechanisms may ultimately allow for the identification of multiple potential points for prevention or intervention, and for a personalized medicine approach for this subset of environmental-associated ASD cases.

Did you know that your animals have consciousness?

Consciousness is the greatest enigma in human history. For centuries scientists and researchers have tried to describe it without coming to conclusions. In the last years with the neurosciences development, consciousness has become the common goal of numerous studies. But consciousness has always been studied only in humans, but after "Cambridge Declaration on Consciousness" in 2012, even non-human animalsthey feel possessed of the consciousness. According to "theory Orch-OR" of Hameroff and Penrose we have conducted a study on Alaskan malamute and German shepherd to analysed a triplet of platelet fatty acids (linoleic acid; palmitic acid; arachidonic acid). Through these analysis and the relative mapping of subjects within a SOM it was possible to make an assessment of the possible onset of mood disorders in the dogs. A critical analysis of the results obtained shows that animals have molecular analogies with humans compared to mood disorders. The German shepherd and Alaskan malamute, indeed, have, in the case of major depression, a bio-chemical profile, the most similar to man.

Does Childhood Trauma Moderate Polygenic Risk for Depression? A Meta-analysis of 5765 Subjects From the Psychiatric Genomics Consortium

BACKGROUND

The heterogeneity of genetic effects on major depressive disorder (MDD) may be partly attributable to moderation of genetic effects by environment, such as exposure to childhood trauma (CT). Indeed, previous findings in two independent cohorts showed evidence for interaction between polygenic risk scores (PRSs) and CT, albeit in opposing directions. This study aims to meta-analyze MDD-PRS × CT interaction results across these two and other cohorts, while applying more accurate PRSs based on a larger discovery sample.

METHODS

Data were combined from 3024 MDD cases and 2741 control subjects from nine cohorts contributing to the MDD Working Group of the Psychiatric Genomics Consortium. MDD-PRS were based on a discovery sample of ∼110,000 independent individuals. CT was assessed as exposure to sexual or physical abuse during childhood. In a subset of 1957 cases and 2002 control subjects, a more detailed five-domain measure additionally included emotional abuse, physical neglect, and emotional neglect.

RESULTS

MDD was associated with the MDD-PRS (odds ratio [OR] = 1.24, p = 3.6 × 10-5, R2 = 1.18%) and with CT (OR = 2.63, p = 3.5 × 10-18 and OR = 2.62, p = 1.4 ×10-5 for the two- and five-domain measures, respectively). No interaction was found between MDD-PRS and the two-domain and five-domain CT measure (OR = 1.00, p = .89 and OR = 1.05, p = .66).

CONCLUSIONS

No meta-analytic evidence for interaction between MDD-PRS and CT was found. This suggests that the previously reported interaction effects, although both statistically significant, can best be interpreted as chance findings. Further research is required, but this study suggests that the genetic heterogeneity of MDD is not attributable to genome-wide moderation of genetic effects by CT.

The 5-HTTLPR genotype, early life adversity and cortisol responsivity to psychosocial stress in women

BACKGROUND

The serotonin transporter gene-linked polymorphic region (5-HTTLPR) has previously been associated with hypothalamus-pituitary-adrenal axis function. Moreover, it has been suggested that this association is moderated by an interaction with stressful life experiences.

AIMS

To investigate the moderation of cortisol response to psychosocial stress by 5-HTTLPR genotype, either directly or through an interaction with early life stress.

METHOD

A total of 151 women, 85 of which had personality psychopathology, performed the Trier Social Stress Test while cortisol responsivity was assessed.

RESULTS

The results demonstrate a main effect of genotype on cortisol responsivity. Women carrying two copies of the long version of 5-HTTLPR exhibited stronger cortisol responses to psychosocial stress than women with at least one copy of the short allele (P = 0.03). However, the proportion of the variance of stress-induced cortisol responsivity explained by 5-HTTLPR genotype was not further strengthened by including early life adversity as a moderating factor (P = 0.52).

CONCLUSIONS

Our results highlight the need to clarify gender-specific biological factors influencing the serotonergic system. Furthermore, our results suggest that childhood maltreatment, specifically during the first 15 years of life, is unlikely to exert a moderating influence of large effect on the relationship between the 5-HTTLPR genotype and cortisol responsivity to psychosocial stress.

DECLARATION OF INTEREST

None.

A direct test of the diathesis-stress model for depression

The diathesis-stress theory for depression states that the effects of stress on the depression risk are dependent on the diathesis or vulnerability, implying multiplicative interactive effects on the liability scale. We used polygenic risk scores for major depressive disorder (MDD) calculated from the results of the most recent analysis from the Psychiatric Genomics Consortium as a direct measure of the vulnerability for depression in a sample of 5221 individuals from 3083 families. In the same we also had measures of stressful life events and social support and a depression symptom score, as well as DSM-IV MDD diagnoses for most individuals. In order to estimate the variance in depression explained by the genetic vulnerability, the stressors and their interactions, we fitted linear mixed models controlling for relatedness for the whole sample as well as stratified by sex. We show a significant interaction of the polygenic risk scores with personal life events (0.12% of variance explained, P-value=0.0076) contributing positively to the risk of depression. Additionally, our results suggest possible differences in the aetiology of depression between women and men. In conclusion, our findings point to an extra risk for individuals with combined vulnerability and high number of reported personal life events beyond what would be expected from the additive contributions of these factors to the liability for depression, supporting the multiplicative diathesis-stress model for this disease.

Familial aggregation of major depressive disorder in an African-American community

BACKGROUND

African Americans (AAs) with major depressive disorder (MDD) experience more impairment and poorer treatment outcomes relative to Whites, yet are underrepresented in family studies of MDD. This is the first study to investigate the familial aggregation of major depression among AAs.

METHODS

Participants' reports of depression from clinical and family history (FH) interviews were used to examine depression rates among 435 first-degree relatives and half-siblings of 63 depressed cases and 222 relatives of 33 nondepressed controls. Binary logistic regression was used to compute odds ratios (ORs) for FH of MDD and level of trauma exposure (high and low) in cases versus controls. Poisson regression models with generalized estimating equations were used to assess MDD in relatives of cases versus relatives of controls.

RESULTS

Cases and controls did not differ in either FH of MDD (OR = 1.2, 95% confidence interval [CI] = 0.5-2.9), or prevalence of MDD in relatives (relative risk [RR] = 1.5, 95% CI = 0.8-2.5). However, exposure to high trauma was associated with increased risk of MDD (OR = 3.0, 95% CI = 1.22-7.17) and the combined effect of FH and trauma was greater than expected under an additive model. Similarly, the RR for MDD among relatives of cases with high-trauma levels was 2.2 (1.24-4.2), compared to relatives of controls with low trauma.

CONCLUSION

The effect of FH of MDD appears to be exacerbated among individuals exposed to high trauma. Replication and further research on the chronology and subtypes of trauma and MDD, and their interactions, remain essential in AA populations.

The Use of Antidepressive Agents and Bone Mineral Density in Women: A Meta-Analysis

Antidepressive agents are one of the fastest-growing classes of prescribed drugs. However, the effects of antidepressive agents on bone density are controversial. The aim of this meta-analysis is to evaluate the state of research on the relationship between the use of tricyclic antidepressants (TCAs) or selective serotonin reuptake inhibitors (SSRIs) and bone mineral density (BMD) in women. The database searched was Pubmed. The meta-analysis included human studies in women fulfilling the following criteria: (i) an assessment of bone mineral density in the lumbar spine, the femoral neck or the total hip; (ii) a comparison of the BMD of depressed individuals using antidepressive agents (SSRIs or TCAs), and a control group that did not use antidepressive agents; (iii) measurement of BMD using dual-energy X-ray absorptiometry (DXA); and (iv) calculations of the mean BMD and standard deviation or standard error. Four studies were identified, which, in total, included 934 women using antidepressive agents and 5767 non-using individuals. The results showed that no significant negative composite weighted mean effect sizes were identified for the comparisons between SSRI users and non-users. Similarly, no significant negative composite weighted mean effect sizes were identified for the comparisons between TCA users and non-users, indicating similar BMD in SSRI or TCA users and non-users. The meta-analysis shows that the association between antidepressant medication and bone mineral density has not been extensively researched. Only four studies fulfilled the inclusion criteria. The global result of the literature review and meta-analysis was that the use of antidepressive agents was not associated with lower or higher BMD. This result applies to both SSRIs and TCAs and to all measurement locations (lumbar spine, femoral neck and total hip).

Gene-environment interaction of monoamine oxidase A in relation to antisocial behaviour: current and future directions

Since the pioneering finding of Caspi and co-workers in 2002 that exposure to childhood maltreatment predicted later antisocial behaviour (ASB) in male carriers of the low-activity MAOA-uVNTR allele, frequent replication studies have been published. Two meta-analyses, one in 2006 and the other in 2014, confirmed the original findings by Caspi and co-workers. In the present paper, we review the literature, note some methodological aspects of candidate gene–environment interaction (cG×E) studies and suggest some future directions. Our conclusions are as follows. (1) The direction of the effect in a cG×E model may differ according to the positive and negative environmental background of the population. (2) There is a predictor-intersection problem such that when measuring one type of maltreatment in a person, other kinds of maltreatment often co-occur. Other forms of abuse are implicitly considered in statistical models; therefore, it is difficult to draw conclusions about the effects of timing and the severity of different forms of stressful life events in relation to ASB. (3) There is also an outcome-intersection problem because of the major intersection of ASB and other forms of mental health problems. It is likely that the G×E with MAOA is related to a common unmeasured factor. (4) For the G×E model, in which the effect of the gene on the outcome variable is dependent on other predictor variables, theoretically, hypothesis-driven statistical modelling is needed.

Stress exposure and psychopathology alter methylation of the serotonin receptor 2A (HTR2A) gene in preschoolers

Serotonin signaling pathways play a key role in brain development, stress reactivity, and mental health. Epigenetic alterations in the serotonin system may underlie the effect of early life stress on psychopathology. The current study examined methylation of the serotonin receptor 2A (HTR2A) gene in a sample of 228 children including 119 with child welfare documentation of moderate to severe maltreatment within the last 6 months. Child protection records, semistructured interviews in the home, and parent reports were used to assess child stress exposure, psychiatric symptoms, and behavior. The HTR2A genotype and methylation of HTR2A were measured at two CpG sites (-1420 and -1224) from saliva DNA. HTR2A genotype was associated with HTR2A methylation at both CpG sites. HTR2A genotype also moderated associations of contextual stress exposure and HTR2A methylation at site -1420. Contextual stress was positively associated with -1420 methylation among A homozygotes, but negatively associated with -1420 methylation among G homozygotes. Posttraumatic stress disorder and major depressive disorder symptoms were negatively associated with methylation at -1420, but positively associated with methylation at -1224. Results support the view that the serotonin system is sensitive to stress exposure and psychopathology, and HTR2A methylation may be a mechanism by which early adversity is biologically encoded.

Interactions Among Polymorphisms of Susceptibility Loci for Alzheimer's Disease or Depressive Disorder

Background

Several genetic susceptibility loci for major depressive disorder (MDD) or Alzheimer’s disease (AD) have been described. Interactions among polymorphisms are thought to explain the differences between low- and high-risk groups. We tested for the contribution of interactions between multiple functional polymorphisms in the risk of MDD or AD.

Material/Methods

A genetic association case-control study was performed in 68 MDD cases, 84 AD cases (35 of them with comorbid depression), and 90 controls. The contribution of 7 polymorphisms from 5 genes (APOE, HSPA1A, SLC6A4, HTR2A, and BDNF) related to risk of MDD or AD development was analyzed.

Results

Significant associations were found between MDD and interactions among polymorphisms in HSPA1A, SLC6A4, and BDNF or HSPA1A, BDNF, and APOE genes. For polymorphisms in the APOE gene in AD, significant differences were confirmed on the distributions of alleles and genotype rates compared to the control or MDD. Increased probability of comorbid depression was found in patients with AD who do not carry the ɛ4 allele of APOE.

Conclusions

Assessment of the interactions among polymorphisms of susceptibility loci in both MDD and AD confirmed a synergistic effect of genetic factors influencing inflammatory, serotonergic, and neurotrophic pathways at these heterogenous complex diseases. The effect of interactions was greater in MDD than in AD. A presence of the ɛ4 allele was confirmed as a genetic susceptibility factor in AD. Our findings indicate a role of APOE genotype in onset of comorbid depression in a subgroup of patients with AD who are not carriers of the APOE ɛ4 allele.

Indolethylamine-N-methyltransferase Polymorphisms: Genetic and Biochemical Approaches for Study of Endogenous N,N,-dimethyltryptamine

N,N-dimethyltryptamine (DMT) is a powerful serotonergic psychedelic whose exogenous administration elicits striking psychedelic effects in humans. Studies have identified DMT and analogous compounds (e.g., 5-hydroxy-DMT, 5-methoxy-DMT) alongside of an enzyme capable of synthesizing DMT endogenously from tryptamine, indolethylamine-N-methyltransferase (INMT), in human and several other mammalian tissues. Subsequently, multiple hypotheses for the physiological role of endogenous DMT have emerged, from proposed immunomodulatory functions to an emphasis on the overlap between the mental states generated by exogenous DMT and naturally occurring altered states of consciousness; e.g., schizophrenia. However, no clear relationship between endogenous DMT and naturally occurring altered states of consciousness has yet been established from in vivo assays of DMT in bodily fluids. The advent of genetic screening has afforded the capability to link alterations in the sequence of specific genes to behavioral and molecular phenotypes via expression of identified single nucleotide polymorphisms (SNPs) in cell and animal models. As SNPs in INMT may impact endogenous DMT synthesis and levels via changes in INMT expression and/or INMT structure and function, these combined genetic and biochemical approaches circumvent the limitations of assaying DMT in bodily fluids and may augment data from prior in vitro and in vivo work. Therefore, all reported SNPs in INMT were amassed from genetic and biochemical literature and genomic databases to consolidate a blueprint for future studies aimed at elucidating whether DMT plays a physiological role.

Polymorphism in the serotonin transporter gene polymorphisms (5-HTTLPR) modifies the association between significant life events and depression in people with multiple sclerosis

Background:

In the general population, variation in the serotonin-transporter-linked polymorphic region ( 5-HTTLPR) has been shown to modify the association between stressful events and depression/anxiety. This has not been examined in people with multiple sclerosis (MS).

Objective:

We examined the interaction between significant life events (SLE), 5-HTTLPR and depression/anxiety.

Methods:

A population-based longitudinal cohort of 198 people with MS was followed biannually for 2.5 years. Depression and anxiety symptoms were measured at each review using the Hospital Anxiety and Depression Scale (HADS). SLEs were assessed using a questionnaire based on the Social Readjustment Rating Scale.

Results:

We found an interaction between SLE load in the previous 12 months and functional variation in the 5-HTTLPR allele type in predicting depression, with the association between SLE load and depression being stronger for those with S/S allele type (β = 0.21 (95% confidence interval (CI): 0.09–0.33) per 10-unit increase) and S/L (β = 0.14 (95% CI: 0.05–0.24)) compared to L/L allele type (β = 0.04 (95% CI: −0.05 to 0.24); pinteraction < 0.001). No convincing evidence of an interaction was found with anxiety.

Conclusion:

We found that the association between SLE load and MS depression severity was stronger among those with one or two copies of the short allele of the 5-HTTLPR. The identification of a gene–environment interaction between SLEs and depression in a population where depression is partly disease-driven is novel.

Assessment of subjective emotional valence and long-lasting impact of life events: development and psychometrics of the Stralsund Life Event List (SEL)

BACKGROUND

Life events (LEs) are associated with future physical and mental health. They are crucial for understanding the pathways to mental disorders as well as the interactions with biological parameters. However, deeper insight is needed into the complex interplay between the type of LE, its subjective evaluation and accompanying factors such as social support. The "Stralsund Life Event List" (SEL) was developed to facilitate this research.

METHODS

The SEL is a standardized interview that assesses the time of occurrence and frequency of 81 LEs, their subjective emotional valence, the perceived social support during the LE experience and the impact of past LEs on present life. Data from 2265 subjects from the general population-based cohort study "Study of Health in Pomerania" (SHIP) were analysed. Based on the mean emotional valence ratings of the whole sample, LEs were categorized as "positive" or "negative". For verification, the SEL was related to lifetime major depressive disorder (MDD; Munich Composite International Diagnostic Interview), childhood trauma (Childhood Trauma Questionnaire), resilience (Resilience Scale) and subjective health (SF-12 Health Survey).

RESULTS

The report of lifetime MDD was associated with more negative emotional valence ratings of negative LEs (OR = 2.96, p < 0.0001). Negative LEs (b = 0.071, p < 0.0001, β = 0.25) and more negative emotional valence ratings of positive LEs (b = 3.74, p < 0.0001, β = 0.11) were positively associated with childhood trauma. In contrast, more positive emotional valence ratings of positive LEs were associated with higher resilience (b = - 7.05, p < 0.0001, β = 0.13), and a lower present impact of past negative LEs was associated with better subjective health (b = 2.79, p = 0.001, β = 0.05). The internal consistency of the generated scores varied considerably, but the mean value was acceptable (averaged Cronbach's alpha > 0.75).

CONCLUSIONS

The SEL is a valid instrument that enables the analysis of the number and frequency of LEs, their emotional valence, perceived social support and current impact on life on a global score and on an individual item level. Thus, we can recommend its use in research settings that require the assessment and analysis of the relationship between the occurrence and subjective evaluation of LEs as well as the complex balance between distressing and stabilizing life experiences.

The usefulness and interpretation of systematic reviews

Keeping up to date with the best evidence on treatment interventions is an essential part of clinical practice, but it can seem an overwhelming task for busy clinicians. Systematic reviews and meta-analyses provide a useful and convenient summary of knowledge and form an essential part of an evidence-based approach to clinical practice. However, these reviews vary in methodology and therefore in the quality of the recommendations they provide. Clinicians need to feel confident in their skills of critical appraisal, so that they can assess the relative merits of systematic reviews. In this article we discuss the strengths and limitations of different types of evidence synthesis to enable the reader to feel more confident in assessing the scientific information to use in clinical practice.

Epigenetics applied to psychiatry: Clinical opportunities and future challenges

Psychiatric disorders are clinically heterogeneous and debilitating chronic diseases resulting from a complex interplay between gene variants and environmental factors. Epigenetic processes, such as DNA methylation and histone posttranslational modifications, instruct the cell/tissue to correctly interpret external signals and adjust its functions accordingly. Given that epigenetic modifications are sensitive to environment, stable, and reversible, epigenetic studies in psychiatry could represent a promising approach to better understanding and treating disease. In the present review, we aim to discuss the clinical opportunities and challenges arising from the epigenetic research in psychiatry. Using selected examples, we first recapitulate key findings supporting the role of adverse life events, alone or in combination with genetic risk, in epigenetic programming of neuropsychiatric systems. Epigenetic studies further report encouraging findings about the use of methylation changes as diagnostic markers of disease phenotype and predictive tools of progression and response to treatment. Then we discuss the potential of using targeted epigenetic pharmacotherapy, combined with psychosocial interventions, for future personalized medicine for patients. Finally, we review the methodological limitations that could hinder interpretation of epigenetic data in psychiatry. They mainly arise from heterogeneity at the individual and tissue level and require future strategies in order to reinforce the biological relevance of epigenetic data and its translational use in psychiatry. Overall, we suggest that epigenetics could provide new insights into a more comprehensive interpretation of mental illness and might eventually improve the nosology, treatment, and prevention of psychiatric disorders.

Gene-environment Interactions in Late Life: Linking Psychosocial Stress with Brain Aging

Gene-environment interactions (GxE) can have lasting consequences on brain structure and function, potentially contributing to diverse neuropsychiatric phenotypes. This has been extensively demonstrated by studies examining GxE in childhood and early adulthood, whereas much fewer studies have addressed this question in late life. The relative paucity of studies examining GxE in late life may stem from the working hypothesis that brains become less malleable to environmental inputs as life progresses. However, while some components of brain plasticity decline with increasing age, others are retained and may even become more pronounced in old ages. Moreover, the micro- and macro-structural brain changes that accrue as a result of aging-related morbidities are likely to accentuate the susceptibility of neural circuits to environmental stressors as life advances. Supporting this hypothesis, psychosocial stress can increase the risk for late-life neuropsychiatric syndromes, especially when afflicting genetically predisposed individuals. This article reviews evidence showing how gene-stress interactions can impact the aging brain and related phenotypes in late life, and it discusses the potential mechanisms underlying such GxE and their implications for the prevention and treatment of late-life neuropsychiatric syndromes.

Significance of risk polymorphisms for depression depends on stress exposure

Depression is a polygenic and multifactorial disorder where environmental effects exert a significant impact, yet most genetic studies do not consider the effect of stressors which may be one reason for the lack of replicable results in candidate gene studies, GWAS and between human studies and animal models. Relevance of functional polymorphisms in seven candidate genes previously implicated in animal and human studies on a depression-related phenotype given various recent stress exposure levels was assessed with Bayesian relevance analysis in 1682 subjects. This Bayesian analysis indicated a gene-environment interaction whose significance was also tested with a traditional multivariate analysis using general linear models. The investigated genetic factors were only relevant in the moderate and/or high stress exposure groups. Rank order of genes was GALR2 > BDNF > P2RX7 > HTR1A > SLC6A4 > CB1 > HTR2A, with strong relevance for the first four. Robust gene-gene-environment interaction was found between BDNF and HTR1A. Gene-environment interaction effect was confirmed, namely no main effect of genes, but a significant modulatory effect on environment-induced development of depression were found. Our data support the strong causative role of the environment modified by genetic factors, similar to animal models. Gene-environment interactions point to epigenetic factors associated with risk SNPs. Galanin-2 receptor, BDNF and X-type purin-7 receptor could be drug targets for new antidepressants.

A BRIEF INTRODUCTION TO THE NEUROGENETICS OF COGNITION-EMOTION INTERACTIONS

Neuroscience research has demonstrated that cognition, emotion, and their dynamic interactions emerge from complex and flexible patterns of activity across distributed neural circuits. A parallel branch of research in genetics has begun to identify common variation in the human DNA sequence (i.e., genome) that may shape individual differences in cognition-emotion interactions by altering molecular and cellular pathways that modulate the activity of these neural circuits. Here we provide a brief introduction to such neurogenetics research and how it may usefully inform our understanding of the biological mechanisms through which dynamic cognition-emotion interactions emerge and, subsequently, help shape normal and abnormal behavior.

BDNF Val66Met polymorphism, life stress and depression: A meta-analysis of gene-environment interaction

BACKGROUND

Depression is thought to be multifactorial in etiology, including genetic and environmental components. While a number of gene-environment interaction studies have been carried out, meta-analyses are scarce. The present meta-analysis aimed to quantify evidence on the interaction between brain-derived neurotrophic factor (BDNF) Val66Met polymorphism and stress in depression.

METHODS

Included were 31 peer-reviewed with a pooled total of 21060 participants published before October 2016 and literature searches were conducted using PubMed, Wolters Kluwer, Web of Science, EBSCO, Elsevier Science Direct and Baidu Scholar databases.

RESULTS

The results indicated that the Met allele of BDNF Val66Met polymorphism significantly moderated the relationship between stress and depression (Z=2.666, p = 0.003). The results of subgroup analysis concluded that stressful life events and childhood adversity separately interacted with the Met allele of BDNF Val66Met polymorphism in depression (Z = 2.552, p = 0.005; Z = 1.775, p = 0.03).

LIMITATIONS

The results could be affected by errors or bias in primary studies which had small sample sizes with relatively lower statistic power. We could not estimate how strong the interaction effect between gene and environment was.

CONCLUSIONS

We found evidence that supported the hypothesis that BDNF Val66Met polymorphism moderated the relationship between stress and depression, despite the fact that many included individual studies did not show this effect.

New resilience instrument for patients with cancer

OBJECTIVE

Resilience is an important concept in the cancer literature and is a salient indicator of cancer survivorship. The aim of this study is to develop and validate a new resilience instrument that is specific to patients with cancer diagnosis (RS-SC) in Mainland China.

METHODS

First, a resilience framework was constructed for patients with cancer diagnosis. Second, items were formulated based on the framework to reflect different aspects of resilience. Third, two rounds of expert panel discussion were performed to select important and relevant items. Finally, two cross-sectional studies were conducted to evaluate the psychometric properties of this instrument.

RESULTS

Fifty-one items were generated based on the resilience framework and the final 25-item RS-SC resulted in a five-factor solution including Generic Elements, Benefit Finding, Support and Coping, Hope for the Future and Meaning for Existence, accounting for 64.72% of the variance. The Cronbach's α of the RS-SC was 0.825 and the test-retest reliability was 0.874.

CONCLUSION

The RS-SC is a brief and specific self-report resilience instrument for Chinese patients with cancer and shows sound psychometric properties in this study. The RS-SC has potential applications in both clinical practice and research with strength-based resiliency interventions.

Pupil mimicry and trust - Implication for depression

Individuals suffering from depression often have difficulty trusting others. Previous research has shown a relationship between trust formation and pupil mimicry - the synchronization of pupil sizes between individuals. The current study therefore examined whether pupil mimicry is weaker in depressed individuals and an underlying factor of their low levels of trust. Forty-two patients with major depressive disorder (MDD) and 40 healthy control subjects played trust games with virtual partners. Images of these partners' eye regions were presented to participants before they had to make a monetary investment decision. Partners' pupils either dilated, constricted, or remained static over the course of 4-s interactions. During the task, participants' pupil sizes were recorded with eye-tracking equipment to assess mimicry. The results confirm that patients with MDD were somewhat less trusting than controls and used another's pupillary cues differently when deciding to trust. Specifically, whereas healthy controls trusted partners with dilating pupils more than partners with constricting pupils, patients with MDD particularly trusted partners whose pupils changed in size less, regardless of whether partners' pupils were dilating or constricting. This difference in investment behavior was unrelated to differences in pupil mimicry, which was equally apparent in both groups and fostered trust to the same extent. Whereas lower levels of trust observed in patients with MDD could not be explained by differences in pupil mimicry, our data show that pupil dilation mimicry might help people to trust. These findings provide further evidence for the important role of pupil size and pupil mimicry in interpersonal trust formation and shed light on the pathophysiology of clinically low trust in patients with MDD.

Effects of repeated long-term psychosocial stress and acute cannabinoid exposure on mouse corticostriatal circuitries: Implications for neuropsychiatric disorders

Introduction

Vulnerability to psychiatric manifestations is achieved by the influence of genetic and environment including stress and cannabis consumption. Here, we used a psychosocial stress model based on resident‐intruder confrontations to study the brain corticostriatal‐function, since deregulation of corticostriatal circuitries has been reported in many psychiatric disorders. CB₁ receptors are widely expressed in the central nervous system and particularly, in both cortex and striatum brain structures.

Aims and methods

The investigation presented here is addressed to assess the impact of repeated stress following acute cannabinoid exposure on behavior and corticostriatal brain physiology by assessing mice behavior, the concentration of endocannabinoid and endocannabinoid‐like molecules and changes in the transcriptome.

Results

Stressed animals urinated frequently; showed exacerbated scratching activity, lower striatal N‐arachidonylethanolamine (AEA) levels and higher cortical expression of cholinergic receptor nicotinic alpha 6. The cannabinoid agonist WIN55212.2 diminished locomotor activity while the inverse agonist increased the distance travelled in the center of the open field. Upon CB₁ activation, N‐oleoylethanolamide and N‐palmitoylethanolamide, two AEA congeners that do not interact directly with cannabinoid receptors, were enhanced in the striatum. The co‐administration with both cannabinoids induced an up‐regulation of striatal FK506 binding protein 5. The inverse agonist in controls reversed the effects of WIN55212.2 on motor activity. When Rimonabant was injected under stress, the cortical levels of 2‐arachidonoylglycerol were maximum. The agonist and the antagonist influenced the cortical expression of cholinergic receptor nicotinic alpha 6 and serotonin transporter neurotransmitter type 4 in opposite directions, while their co‐administration tended to produce a null effect under stress.

Conclusions

The endocannabinoid system had a direct effect on serotoninergic neurotransmission and glucocorticoid signaling. Cholinergic receptor nicotinic alpha‐6 was shown to be deregulated in response to stress and following synthetic cannabinoid drugs thus could confer vulnerability to cannabis addiction and psychosis. Targeting the receptors of endocannabinoids and endocannabinoid‐like mediators might be a valuable option for treating stress‐related neuropsychiatric symptoms.

Association Study and Meta-Analysis of Polymorphisms, Methylation Profiles, and Peripheral mRNA Expression of the Serotonin Transporter Gene in Patients with Alzheimer's Disease

BACKGROUND/AIM

The aim of this study was to elucidate the relationship between Alzheimer's disease (AD) and the serotonin transporter gene (SLC6A4).

METHODS

AD subjects (n = 43) and controls (n = 47) were recruited and evaluated. In leukocytes, we evaluated two polymorphisms in SLC6A4, the serotonin transporter length polymorphic region (5-HTT-LPR) and rs25531, as well as methylation rates of the SLC6A4 promoter region and the SLC6A4 mRNA expression level. We also performed a meta-analysis to examine the relationship between the frequency of the L allele and the risk of AD.

RESULTS

The distributions of 5-HTT-LPR and rs25531 polymorphisms in AD subjects were not different from those of controls. Although the methylation rates in AD subjects were not significantly different from those of controls, the expression level in AD subjects was significantly higher than in controls. Additionally, the expression level in AD subjects was significantly correlated with apathy. Meta-analysis revealed that the L/L genotype significantly reduced the risk of AD, but only in the Caucasian population.

CONCLUSION

Higher SLC6A4 mRNA expression in leukocytes in AD was associated with apathy regardless of SLC6A4 genotypes and methylation rates of the promoter region. The L/L genotype may reduce the risk of AD in the Caucasian population.

Association of Protein Distribution and Gene Expression Revealed by PET and Post-Mortem Quantification in the Serotonergic System of the Human Brain

Regional differences in posttranscriptional mechanisms may influence in vivo protein densities. The association of positron emission tomography (PET) imaging data from 112 healthy controls and gene expression values from the Allen Human Brain Atlas, based on post-mortem brains, was investigated for key serotonergic proteins. PET binding values and gene expression intensities were correlated for the main inhibitory (5-HT1A) and excitatory (5-HT2A) serotonin receptor, the serotonin transporter (SERT) as well as monoamine oxidase-A (MAO-A), using Spearman's correlation coefficients (rs) in a voxel-wise and region-wise analysis. Correlations indicated a strong linear relationship between gene and protein expression for both the 5-HT1A (voxel-wise rs = 0.71; region-wise rs = 0.93) and the 5-HT2A receptor (rs = 0.66; 0.75), but only a weak association for MAO-A (rs = 0.26; 0.66) and no clear correlation for SERT (rs = 0.17; 0.29). Additionally, region-wise correlations were performed using mRNA expression from the HBT, yielding comparable results (5-HT1Ars = 0.82; 5-HT2Ars = 0.88; MAO-A rs = 0.50; SERT rs = -0.01). The SERT and MAO-A appear to be regulated in a region-specific manner across the whole brain. In contrast, the serotonin-1A and -2A receptors are presumably targeted by common posttranscriptional processes similar in all brain areas suggesting the applicability of mRNA expression as surrogate parameter for density of these proteins.

Gene-environment interactions between stress and 5-HTTLPR in depression: A meta-analytic update

BACKGROUND

Meta-analyses have yielded contradictory findings concerning the role of 5-HTTLPR in interaction with stress (GxE) in depression. The current meta-analysis investigates if these contradictory findings are a result of differences between studies in methodological approaches towards the assessment of stress and depression.

METHODS

After performing a systematic database search (February to December 2016), first, a meta-analysis was used to investigate the total effect size and publication bias. Second, stratified meta-analyses were used to investigate the potential moderating influence of different methodological approaches on heterogeneity of study findings. Third, a meta-regression was used to investigate the combined influence of the methodological approaches on the overall effect size.

RESULTS

Results showed a small but significant effect of 5-HTTLPR in interaction with stress in the prediction of depression (OR[95%CI] = 1.18[1.09; 1.28], n = 48 effect sizes from 51 studies, totaling 51,449 participants). There was no evidence of publication bias. Heterogeneity of effect sizes was a result of outliers and not due to different methodological approaches towards the assessment of stress and depression. Yet, there was some evidence that studies adopting a categorical and interview approach to the assessment of stress report higher GxE effects, but further replication of this finding is needed.

LIMITATIONS

A large amount of heterogeneity (i.e., 46%) was not explained by the methodological factors included in the study and there was a low response rate of invited studies.

CONCLUSIONS

The current meta-analysis provides new evidence for the robustness of the interaction between stress and 5-HTTLPR in depression.

Associations between stress and depression symptom profiles vary according to serotonin transporter polymorphism in rural Australians

PURPOSE

Depression remains difficult to treat in all cases, and further investigation of the role of genetic and environmental factors may be valuable. This study was designed to investigate the association between the short (s) versus non-short (non-s) 5HTTLPR variants, presence of childhood stressors and recent life stressors, and depression, and to do so at two levels that would expose the associations between total depression scores and also individual depression items.

MATERIALS AND METHODS

Two hundred and forty-nine volunteers from one of the Australian Electoral Office electorates covering a large rural land area completed a series of questionnaires about childhood and recent life stress and depression, and provided a buccal cell sample for genotyping the 5-HTTLPR polymorphism into s versus non-s carriers.

RESULTS

Although there were no significant differences in the depression scores of the s-carriers versus the non-s carriers, each subtype of the 5-HTTLPR polymorphism showed different patterns of association between childhood stress and depression symptoms, and between recent life stress and depression symptoms.

CONCLUSION

Individualization of therapy for depression may be achieved through consideration of the specific associations that patients exhibit between life stress, 5-HTTLPR polymorphism, and depression symptomatology.

Nested positive feedback loops in the maintenance of major depression: An integration and extension of previous models

Several theories of Major Depressive Disorder (MDD) have previously been proposed, focusing largely on either a psychological (i.e., cognitive/affective), biological, or neural/computational level of description. These theories appeal to somewhat distinct bodies of work that have each highlighted separate factors as being of considerable potential importance to the maintenance of MDD. Such factors include a range of cognitive/attentional information-processing biases, a range of structural and functional brain abnormalities, and also dysregulation within the autonomic, endocrine, and immune systems. However, to date there have been limited efforts to integrate these complimentary perspectives into a single multi-level framework. Here we review previous work in each of these MDD research domains and illustrate how they can be synthesized into a more comprehensive model of how a depressive episode is maintained. In particular, we emphasize how plausible (but insufficiently studied) interactions between the various MDD-related factors listed above can lead to a series of nested positive feedback loops, which are each capable of maintaining an individual in a depressive episode. We also describe how these different feedback loops could be active to different degrees in different individual cases, potentially accounting for heterogeneity in both depressive symptoms and treatment response. We conclude by discussing how this integrative model might extend understanding of current treatment mechanisms, and also potentially guide the search for markers to inform treatment selection in individual cases.

Serotonin Transporter Gene (SLC6A4) Polymorphism May Be Associated with Chinese Globus Pharyngeus and Its Antidepressant Effects

BACKGROUND

Although globus pharyngeus is not rare in clinical practice, little is known about its associated gene polymorphism. We investigated the association between the SLC6A4 polymorphism and globus pharyngeus and its response to treatment with antidepressants.

METHODS

A total of 84 patients were diagnosed with globus pharyngeus according to Rome III, and 160 healthy controls were genotyped for the SLC6A4 polymorphism using polymerase chain reaction amplification and agarose gel electrophoresis. All patients with globus were studied using high-resolution manometry pre-therapy. Globus patients were randomized into paroxetine or amitriptyline groups for a 6-week treatment and asked to complete the following pre- and post-therapy questionnaires: the Glasgow Edinburgh Throat Scale (GETS), the Pittsburgh Sleep Quality Index, and the Hamilton Rating Scale Anxiety/Depression. Treatment response was defined as a >50% reduction in the GETS scores.

RESULTS

A significant difference was observed in the globus S/S genotype with anxiety compared to that without anxiety (χ2 = 14.579, p = 0.006). The L/S genotype showed a significant difference between high upper esophageal sphincter pressure (>104 mm Hg) and non-high upper esophageal sphincter pressure patients (χ2 = 14.433, p = 0.006). A significant association between the S/S genotype and the response to antidepressant treatment was also observed, while patients with sleep disorders or depression showed no association.

CONCLUSION

A significant association was observed between the S/S genotype of the SLC6A4 polymorphism and globus pharyngeus, suggesting that SLC6A4 is a potential candidate gene involved in the pathogenesis of globus pharyngeus.

Biological underpinnings of an internalizing pathway to alcohol, cigarette, and marijuana use

There is a limited understanding as to how specific genes impact addiction risk. Applying a developmental framework and research domain criteria (RDoC) to identify etiological pathways from genetic markers to addiction may have utility. Prior research has largely focused on externalizing pathways to substance use. Although internalizing mechanisms have received less attention, there is strong support that addiction is a longer term consequence of using substances to cope with internalizing as well as externalizing problems. This study tests whether temperament and depression mediate the association between specific genetic variants and substance use. The sample consisted of 426 adolescents from the Michigan Longitudinal Study (70.9% boys, 84.0% White). Four specific genetic variants were examined: SLC6A4 (5HTTLPR), BDNF (rs6265), NPY (rs3037354), and CRHBP (rs7728378). Childhood resiliency and behavioral control were examined as potential mediators, in addition to early adolescent depression, using a multiple-mediator path model. Resiliency and depression were supported as mediators in the association between genetic risk and later substance use. Important differences emerged across substances of abuse. Indirect effects via depression were not significant with the inclusion of aggression. Early difficulties with emotional coping may represent nonspecific neurobiological underpinnings for an internalizing pathway to addiction. (PsycINFO Database Record

Treatment resistant depression: A multi-scale, systems biology approach

An estimated 50% of depressed patients are inadequately treated by available interventions. Even with an eventual recovery, many patients require a trial and error approach, as there are no reliable guidelines to match patients to optimal treatments and many patients develop treatment resistance over time. This situation derives from the heterogeneity of depression and the lack of biomarkers for stratification by distinct depression subtypes. There is thus a dire need for novel therapies. To address these known challenges, we propose a multi-scale framework for fundamental research on depression, aimed at identifying the brain circuits that are dysfunctional in several animal models of depression as well the changes in gene expression that are associated with these models. When combined with human genetic and imaging studies, our preclinical studies are starting to identify candidate circuits and molecules that are altered both in models of disease and in patient populations. Targeting these circuits and mechanisms can lead to novel generations of antidepressants tailored to specific patient populations with distinctive types of molecular and circuit dysfunction.

Collaborative meta-analysis finds no evidence of a strong interaction between stress and 5-HTTLPR genotype contributing to the development of depression

The hypothesis that the S allele of the 5-HTTLPR serotonin transporter promoter region is associated with increased risk of depression, but only in individuals exposed to stressful situations, has generated much interest, research and controversy since first proposed in 2003. Multiple meta-analyses combining results from heterogeneous analyses have not settled the issue. To determine the magnitude of the interaction and the conditions under which it might be observed, we performed new analyses on 31 data sets containing 38 802 European ancestry subjects genotyped for 5-HTTLPR and assessed for depression and childhood maltreatment or other stressful life events, and meta-analysed the results. Analyses targeted two stressors (narrow, broad) and two depression outcomes (current, lifetime). All groups that published on this topic prior to the initiation of our study and met the assessment and sample size criteria were invited to participate. Additional groups, identified by consortium members or self-identified in response to our protocol (published prior to the start of analysis) with qualifying unpublished data, were also invited to participate. A uniform data analysis script implementing the protocol was executed by each of the consortium members. Our findings do not support the interaction hypothesis. We found no subgroups or variable definitions for which an interaction between stress and 5-HTTLPR genotype was statistically significant. In contrast, our findings for the main effects of life stressors (strong risk factor) and 5-HTTLPR genotype (no impact on risk) are strikingly consistent across our contributing studies, the original study reporting the interaction and subsequent meta-analyses. Our conclusion is that if an interaction exists in which the S allele of 5-HTTLPR increases risk of depression only in stressed individuals, then it is not broadly generalisable, but must be of modest effect size and only observable in limited situations.

Interaction between childhood maltreatment on immunogenetic risk in depression: Discovery and replication in clinical case-control samples

Major depressive disorder (MDD) is a prevalent disorder with moderate heritability. Both MDD and interpersonal adversity, including childhood maltreatment, have been consistently associated with elevated inflammatory markers. We investigated interaction between exposure to childhood maltreatment and extensive genetic variation within the inflammation pathway (CRP, IL1b, IL-6, IL11, TNF, TNFR1, and TNFR2) in relation to depression diagnosis. The discovery RADIANT sample included 262 cases with recurrent DSM-IV/ICD-10 MDD, and 288 unaffected controls. The replication Münster cohort included 277 cases with DSM-IV MDD, and 316 unaffected controls. We identified twenty-five single nucleotide polymorphisms (SNPs) following multiple testing correction that interacted with childhood maltreatment to predict depression in the discovery cohort. Seven SNPs representing independent signals (rs1818879, rs1041981, rs4149576, rs616645, rs17882988, rs1061622, and rs3093077) were taken forward for replication. Meta-analyses of the two samples presented evidence for interaction with rs1818879 (IL6) (RD=0.059, SE=0.016, p<0.001), with the replication Münster sample approaching statistical significance in analyses restricted to recurrent MDD and controls following correction for multiple testing (q=0.066). The CRP locus (rs3093077) showed a similar level of evidence for interaction in the meta-analysis (RD=0.092, SE=0.029, p=0.002), but less compelling evidence in the replication sample alone (recurrent MDD q=0.198; all MDD q=0.126). Here we present evidence suggestive of interaction with childhood maltreatment for novel loci in IL-6 (rs1818879) and CRP (rs3093077), increasing risk of depression. Replication is needed by independent groups, targeting these specific variants and interaction with childhood maltreatment on depression risk.

Genome-wide gene-environment interaction in depression: A systematic evaluation of candidate genes: The childhood trauma working-group of PGC-MDD

Gene by environment (GxE) interaction studies have investigated the influence of a number of candidate genes and variants for major depressive disorder (MDD) on the association between childhood trauma and MDD. Most of these studies are hypothesis driven and investigate only a limited number of SNPs in relevant pathways using differing methodological approaches. Here (1) we identified 27 genes and 268 SNPs previously associated with MDD or with GxE interaction in MDD and (2) analyzed their impact on GxE in MDD using a common approach in 3944 subjects of European ancestry from the Psychiatric Genomics Consortium who had completed the Childhood Trauma Questionnaire. (3) We subsequently used the genome-wide SNP data for a genome-wide case-control GxE model and GxE case-only analyses testing for an enrichment of associated SNPs. No genome-wide significant hits and no consistency among the signals of the different analytic approaches could be observed. This is the largest study for systematic GxE interaction analysis in MDD in subjects of European ancestry to date. Most of the known candidate genes/variants could not be supported. Thus, their impact on GxE interaction in MDD may be questionable. Our results underscore the need for larger samples, more extensive assessment of environmental exposures, and greater efforts to investigate new methodological approaches in GxE models for MDD.

The association of measures of the serotonin system, personality, alcohol use, and smoking with risk-taking traffic behavior in adolescents in a longitudinal study

Studies on the neurobiological basis of risk-taking behavior have most often focused on the serotonin system. The promoter region of the gene encoding the serotonin transporter contains a polymorphic site (5-HTTLPR) that is important for the transcriptional activity, and studies have demonstrated its association with brain activity and behavior. Another molecular mechanism that reflects the capacity of the central serotonin system is the activity of the enzyme monoamine oxidase (MAO) as measured in platelets. The purpose of the present study was to examine how measures of the serotonin system (platelet MAO activity and the 5-HTTLPR polymorphism), personality variables, alcohol use and smoking are associated with risk-taking traffic behavior in schoolchildren through late adolescence. The younger cohort of the longitudinal Estonian Children Personality Behaviour and Health Study (originally n = 583) filled in questionnaires about personality traits, smoking status, alcohol use and traffic behavior at age 15 and 18 years. From venous blood samples, platelet MAO activity was measured radioenzymatically and 5-HTTLPR was genotyped. During late adolescence, subjects with lower platelet MAO activity were more likely to belong to the high-risk traffic behavior group. Male 5-HTTLPRs'-allele carriers were more likely to belong to the high-risk traffic behavior group compared to the l'/l' homozygotes. Other variables predicting risk group were alcohol use, smoking and Maladaptive impulsivity.The results suggest that lower capacity of the serotoninergic system is associated with more risky traffic behavior during late adolescence, but possibly by different mechanisms in boys and girls.

Interaction between early-life stress and FKBP5 gene variants in major depressive disorder and post-traumatic stress disorder: A systematic review and meta-analysis

BACKGROUND

Gene-environment interaction contributes to the risks of psychiatric disorders. Interactions between FKBP5 gene variants and early-life stress may enhance the risk not only for mood disorder, but also for a number of other behavioral phenotypes. The aim of the present study was to review and conduct a meta-analysis on the results from published studies examining interaction between FKBP5 gene variants and early-life stress and their associations with stress-related disorders such as major depression and PTSD.

METHODS

A literature search was conducted using PsychINFO and PubMed databases until May 2017. A total of 14 studies with a pooled total of 15109 participants met the inclusion criteria, the results of which were combined and a meta-analysis was performed using the differences in correlations as the effect measure. Based on literature, rs1360780, rs3800373, and rs9470080 SNPs were selected within the FKBP5 gene and systematic review was conducted.

RESULTS

Based on the Comprehensive Meta-Analysis software, no publication bias was detected. Sensitivity analysis and credibility of meta-analysis results also indicated that the analyses were stable. The meta-analysis showed that individuals who carry T allele of rs1360780, C-allele of rs3800373 or T-allele of rs9470080 exposed to early-life trauma had higher risks for depression or PTSD.

LIMITATIONS

The effects of ethnicity, age, sex, and different stress measures were not examined due to limited sample size.

CONCLUSIONS

These results provide strong evidence of interactions between FKBP5 genotypes and early-life stress, which could pose a significant risk factor for stress-associated disorders such as major depression and PTSD.

FoxO1, A2M, and TGF-β1: three novel genes predicting depression in gene X environment interactions are identified using cross-species and cross-tissues transcriptomic and miRNomic analyses

To date, gene-environment (GxE) interaction studies in depression have been limited to hypothesis-based candidate genes, since genome-wide (GWAS)-based GxE interaction studies would require enormous datasets with genetics, environmental, and clinical variables. We used a novel, cross-species and cross-tissues "omics" approach to identify genes predicting depression in response to stress in GxE interactions. We integrated the transcriptome and miRNome profiles from the hippocampus of adult rats exposed to prenatal stress (PNS) with transcriptome data obtained from blood mRNA of adult humans exposed to early life trauma, using a stringent statistical analyses pathway. Network analysis of the integrated gene lists identified the Forkhead box protein O1 (FoxO1), Alpha-2-Macroglobulin (A2M), and Transforming Growth Factor Beta 1 (TGF-β1) as candidates to be tested for GxE interactions, in two GWAS samples of adults either with a range of childhood traumatic experiences (Grady Study Project, Atlanta, USA) or with separation from parents in childhood only (Helsinki Birth Cohort Study, Finland). After correction for multiple testing, a meta-analysis across both samples confirmed six FoxO1 SNPs showing significant GxE interactions with early life emotional stress in predicting depressive symptoms. Moreover, in vitro experiments in a human hippocampal progenitor cell line confirmed a functional role of FoxO1 in stress responsivity. In secondary analyses, A2M and TGF-β1 showed significant GxE interactions with emotional, physical, and sexual abuse in the Grady Study. We therefore provide a successful 'hypothesis-free' approach for the identification and prioritization of candidate genes for GxE interaction studies that can be investigated in GWAS datasets.

The CogBIAS longitudinal study protocol: cognitive and genetic factors influencing psychological functioning in adolescence

BACKGROUND

Optimal psychological development is dependent upon a complex interplay between individual and situational factors. Investigating the development of these factors in adolescence will help to improve understanding of emotional vulnerability and resilience. The CogBIAS longitudinal study (CogBIAS-L-S) aims to combine cognitive and genetic approaches to investigate risk and protective factors associated with the development of mood and impulsivity-related outcomes in an adolescent sample.

METHODS

CogBIAS-L-S is a three-wave longitudinal study of typically developing adolescents conducted over 4 years, with data collection at age 12, 14 and 16. At each wave participants will undergo multiple assessments including a range of selective cognitive processing tasks (e.g. attention bias, interpretation bias, memory bias) and psychological self-report measures (e.g. anxiety, depression, resilience). Saliva samples will also be collected at the baseline assessment for genetic analyses. Multilevel statistical analyses will be performed to investigate the developmental trajectory of cognitive biases on psychological functioning, as well as the influence of genetic moderation on these relationships.

DISCUSSION

CogBIAS-L-S represents the first longitudinal study to assess multiple cognitive biases across adolescent development and the largest study of its kind to collect genetic data. It therefore provides a unique opportunity to understand how genes and the environment influence the development and maintenance of cognitive biases and provide insight into risk and protective factors that may be key targets for intervention.

Understanding the pathophysiology of depression: From monoamines to the neurogenesis hypothesis model - are we there yet?

A number of factors (biogenic amine deficiency, genetic, environmental, immunologic, endocrine factors and neurogenesis) have been identified as mechanisms which provide unitary explanations for the pathophysiology of depression. Rather than a unitary construct, the combination and linkage of these factors have been implicated in the pathogenesis of depression. That is, environmental stressors and heritable genetic factors acting through immunologic and endocrine responses initiate structural and functional changes in many brain regions, resulting in dysfunctional neurogenesis and neurotransmission which then manifest as a constellation of symptoms which present as depression.

5-HTTLPR polymorphism is associated with nostalgia proneness: The role of neuroticism

Nostalgia, a sentimental longing for the past, is a self-relevant and social emotion. Nostalgia proneness is associated with alleviation of distress or instability (e.g., neuroticism). Although nostalgia proneness is heritable, the specific molecular contributors to this heritability are unknown. We focused on a polymorphism in the promoter of the serotonin transporter gene (5-HTTLPR) as a possible biological basis of nostalgia proneness, because the serotonin system has been associated with sensitivity to negative experience. Participants (N = 397 adults) who had reported levels of nostalgia proneness were genotyped. A subsample also completed a measure of neuroticism. Participants with the 5-HTTLPR short allele were higher on nostalgia proneness than those without this allele. Neuroticism mediated the relation between 5-HTTLPR and nostalgia proneness. These findings enrich our understanding of the genetic and personality underpinnings of nostalgia.

Early life stress predicts negative urgency through brooding, depending on 5-HTTLPR genotype: A pilot study with 6-month follow-up examining suicide ideation

The present study examined the interaction between early life stress and 5-HTT genotypes in predicting two risk factors for suicidal behavior - the brooding subtype of rumination and impulsivity, in the form of negative urgency - over time. Furthermore, we examined early life stress, brooding, and impulsivity as predictors of suicidal ideation over time. Participants with and without a history of early life stress were genotyped for the 5-HTTLPR polymorphism and completed assessments assessing brooding and negative urgency at baseline and 6-month follow up. Early life emotional abuse was associated with negative urgency at follow-up. We found an indirect effect of early life emotional abuse on negative urgency through brooding among individuals with 5-HTT low expressing genotypes but not among individuals with 5-HTT high expressing genotypes. Further, a logistic regression analysis revealed that negative urgency was associated with higher odds (O.R. = 16.2) of reporting suicide ideation (versus no ideation) at follow-up. Our findings suggest that brooding and negative urgency may result from the interaction between early life emotional abuse and 5-HTT low expressing genotypes. Further research is necessary to understand how early life stress interacts with 5-HTT genotypes to confer risk for suicidal behavior through psychological mechanisms.

Stressful life events during adolescence and risk for externalizing and internalizing psychopathology: a meta-analysis

The main objective of the present research was to analyze the relations between stressful life events and the externalizing and internalizing spectra of psychopathology using meta-analytical procedures. After removing the duplicates, a total of 373 papers were found in a literature search using several bibliographic databases, such as the PsycINFO, Medline, Scopus, and Web of Science. Twenty-seven studies were selected for the meta-analytical analysis after applying different inclusion and exclusion criteria in different phases. The statistical procedure was performed using a random/mixed-effects model based on the correlations found in the studies. Significant positive correlations were found in cross-sectional and longitudinal studies. A transactional effect was then found in the present study. Stressful life events could be a cause, but also a consequence, of psychopathological spectra. The level of controllability of the life events did not affect the results. Special attention should be given to the usage of stressful life events in gene-environment interaction and correlation studies, and also for clinical purposes.