Stressful life events, 5-HTT genotype and risk of depression

Association between chronic disease status and transitions in depressive symptoms among middle-aged and older Chinese population: Insights from a Markov model-based cohort study

BACKGROUND

The relationship between chronic disease status (CDS) and transitions in depressive symptoms (DS) remains unclear. This study explores the association between CDS and DS transitions.

METHODS

This cohort study analyzed data from 8175 participants aged 45+, sourced from China Family Panel Studies (2016, 2018, 2020). DS were assessed using a brief version of Center for Epidemiologic Studies Depression Scale (CES-D). CDS was categorized into healthy, single disease, and multimorbidity. Markov models were used to estimate state transition intensities, mean sojourn times and hazard ratios (HRs).

RESULTS

DS transitions occurred between adjacent and non-adjacent states, but transition intensity between adjacent states was higher than among non-adjacent states. Self-transition intensities of severe-DS, mild-DS, and non-DS progressively increased, with average durations of 1.365, 1.482, and 7.854 years, respectively. Both single disease and multimorbidity were significantly associated with an increased risk of transitioning from non-DS to mild-DS, with multimorbidity showing a stronger association. In contrast, HRs for single diseases transitioning from mild-DS to severe-DS were significantly lower than 1. Furthermore, their HRs were almost <1 in recovery transitions but not statistically significant.

LIMITATIONS

Specific chronic diseases and their combinations were not analyzed.

CONCLUSIONS

The progression of DS exhibits various pathways. CDS is associated with DS transitions, but the roles of single disease and multimorbidity may differ across different DS progression stages. Both conditions were significantly linked to the risk of new-onset DS, with multimorbidity posing a greater association. However, this relationship is not observed in other progression stages. These findings could provide insights for early prevention and intervention for DS.

Association of polygenic scores for depression and neuroticism with perceived stress in daily life during a long-lasting stress period

Genetic factors contribute significantly to interindividual differences in the susceptibility to stress-related disorders. As stress can also be conceptualized as environmental exposure, controlled gene-environment interaction (GxE) studies with an in-depth phenotyping may help to unravel mechanisms underlying the interplay between genetic factors and stress. In a prospective-longitudinal quasi-experimental study, we investigated whether polygenic scores (PGS) for depression (DEP-PGS) and neuroticism (NEU-PGS), respectively, were associated with responses to chronic stress in daily life. We examined law students (n = 432) over 13 months. Participants in the stress group experienced a long-lasting stress phase, namely the preparation for the first state examination for law students. The control group consisted of law students without particular stress exposure. In the present manuscript, we analyzed perceived stress levels assessed at high frequency and in an ecologically valid manner by ambulatory assessments as well as depression symptoms and two parameters of the cortisol awakening response. The latter was only assessed in a subsample (n = 196). No associations between the DEP-PGS and stress-related variables were found. However, for the NEU-PGS we found a significant GxE effect. Only in individuals experiencing academic stress a higher PGS for neuroticism predicted stronger increases of perceived stress levels until the exam. At baseline, a higher NEU-PGS was associated with higher perceived stress levels in both groups. Despite the small sample size, we provide preliminary evidence that the genetic disposition for neuroticism is associated with stress level increases in daily life during a long-lasting stress period.

A neural model of vulnerability and resilience to stress-related disorders linked to differential susceptibility

Expert opinion remains divided concerning the impact of putative risk factors on vulnerability to depression and other stress-related disorders. A large body of literature has investigated gene by environment interactions, particularly between the serotonin transporter polymorphism (5-HTTLPR) and negative environments, on the risk for depression. However, fewer studies have simultaneously investigated the outcomes in both negative and positive environments, which could explain some of the inconclusive findings. This is embodied by the concept of differential susceptibility, i.e., the idea that certain common gene polymorphisms, prenatal factors, and traits make some individuals not only disproportionately more susceptible and responsive to negative, vulnerability-promoting environments, but also more sensitive and responsive to positive, resilience-enhancing environmental conditions. Although this concept from the field of developmental psychology is well accepted and supported by behavioral findings, it is striking that its implementation in neuropsychiatric research is limited and that underlying neural mechanisms are virtually unknown. Based on neuroimaging studies that examined how factors mediating differential susceptibility affect brain function, we posit that environmental sensitivity manifests in increased salience network activity, increased salience and default mode network connectivity, and increased salience and central executive network connectivity. These changes in network function may bring about automatic exogenous attention for positive and negative stimuli and flexible attentional set-shifting. We conclude with a call to action; unraveling the neural mechanisms through which differential susceptibility factors mediate vulnerability and resilience may lead us to personalized preventive interventions.

Some Molecular and Cellular Stress Mechanisms Associated with Neurodegenerative Diseases and Atherosclerosis

Chronic stress is a combination of nonspecific adaptive reactions of the body to the influence of various adverse stress factors which disrupt its homeostasis, and it is also a corresponding state of the organism's nervous system (or the body in general). We hypothesized that chronic stress may be one of the causes occurence of several molecular and cellular types of stress. We analyzed literary sources and considered most of these types of stress in our review article. We examined genes and mutations of nuclear and mitochondrial genomes and also molecular variants which lead to various types of stress. The end result of chronic stress can be metabolic disturbance in humans and animals, leading to accumulation of reactive oxygen species (ROS), oxidative stress, energy deficiency in cells (due to a decrease in ATP synthesis) and mitochondrial dysfunction. These changes can last for the lifetime and lead to severe pathologies, including neurodegenerative diseases and atherosclerosis. The analysis of literature allowed us to conclude that under the influence of chronic stress, metabolism in the human body can be disrupted, mutations of the mitochondrial and nuclear genome and dysfunction of cells and their compartments can occur. As a result of these processes, oxidative, genotoxic, and cellular stress can occur. Therefore, chronic stress can be one of the causes forthe occurrence and development of neurodegenerative diseases and atherosclerosis. In particular, chronic stress can play a large role in the occurrence and development of oxidative, genotoxic, and cellular types of stress.

Serotonin and brain function: a tale of two receptors

Previous attempts to identify a unified theory of brain serotonin function have largely failed to achieve consensus. In this present synthesis, we integrate previous perspectives with new and older data to create a novel bipartite model centred on the view that serotonin neurotransmission enhances two distinct adaptive responses to adversity, mediated in large part by its two most prevalent and researched brain receptors: the 5-HT1A and 5-HT2A receptors. We propose that passive coping (i.e. tolerating a source of stress) is mediated by postsynaptic 5-HT1AR signalling and characterised by stress moderation. Conversely, we argue that active coping (i.e. actively addressing a source of stress) is mediated by 5-HT2AR signalling and characterised by enhanced plasticity (defined as capacity for change). We propose that 5-HT1AR-mediated stress moderation may be the brain's default response to adversity but that an improved ability to change one's situation and/or relationship to it via 5-HT2AR-mediated plasticity may also be important - and increasingly so as the level of adversity reaches a critical point. We propose that the 5-HT1AR pathway is enhanced by conventional 5-HT reuptake blocking antidepressants such as the selective serotonin reuptake inhibitors (SSRIs), whereas the 5-HT2AR pathway is enhanced by 5-HT2AR-agonist psychedelics. This bipartite model purports to explain how different drugs (SSRIs and psychedelics) that modulate the serotonergic system in different ways, can achieve complementary adaptive and potentially therapeutic outcomes.

Anti-Apoptotic Protein Bcl-xL Expression in the Midbrain Raphe Region Is Sensitive to Stress and Glucocorticoids

Anti-apoptotic proteins are suggested to be important for the normal health of neurons and synapses as well as for resilience to stress. In order to determine whether stressful events may influence the expression of anti-apoptotic protein Bcl-xL in the midbrain and specifically in the midbrain serotonergic (5-HT) neurons involved in neurobehavioral responses to adverse stimuli, adult male rats were subjected to short-term or chronic forced swim stress. A short-term stress rapidly increased the midbrain bcl-xl mRNA levels and significantly elevated Bcl-xL immunoreactivity in the midbrain 5-HT cells. Stress-induced increase in glucocorticoid secretion was implicated in the observed effect. The levels of bcl-xl mRNA were decreased after stress when glucocorticoid elevation was inhibited by metyrapone (MET, 150 mg/kg), and this decrease was attenuated by glucocorticoid replacement with dexamethasone (DEX; 0.2 mg/kg). Both short-term stress and acute DEX administration, in parallel with Bcl-xL, caused a significant increase in tph2 mRNA levels and slightly enhanced tryptophan hydroxylase immunoreactivity in the midbrain. The increasing effect on the bcl-xl expression was specific to the short-term stress. Forced swim repeated daily for 2 weeks led to a decrease in bcl-xl mRNA in the midbrain without any effects on the Bcl-xL protein expression in the 5-HT neurons. In chronically stressed animals, an increase in tph2 gene expression was not associated with any changes in tryptophan hydroxylase protein levels. Our findings are the first to demonstrate that both short-term stress and acute glucocorticoid exposures induce Bcl-xL protein expression in the midbrain 5-HT neurons concomitantly with the activation of the 5-HT synthesis pathway in these neurons.

Effects of Recent Stress and Variation in the Serotonin Transporter Polymorphism (5-HTTLPR) on Depressive Symptoms: A Repeated-Measures Study of Adults Age 50 and Older

Depending on genetic sensitivity to it, stress may affect depressive symptomatology differentially. Applying the stress-diathesis hypothesis to older adults, we postulate: (1) recent stress will associate with increased depressive symptom levels and (2) this effect will be greater for individuals with at least one short allele of the serotonin transporter gene promoter region (5-HTTLPR). Further, we employ a design that addresses specific limitations of many prior studies that have examined the 5-HTTLPR × SLE relation, by: (a) using a within-person repeated-measures design to address fluctuations that occur within individuals over time, increase power for detecting G × E, and address GE correlation; (b) studying reports of exogenous stressful events (those unlikely to be caused by depression) to help rule out reverse causation and negativity bias, and in order to assess stressors that are more etiologically relevant to depressive symptomatology in older adults. The sample is drawn from the Health and Retirement Study, a U.S. population-based study of older individuals (N = 28,248; mean age = 67.5; 57.3 % female; 80.7 % Non-Hispanic White, 14.9 % Hispanic/Latino, 4.5 % African American; genetic subsample = 12,332), from whom measures of depressive symptoms and exogenous stressors were collected biannually (1994-2010). Variation in the 5-HTTLPR was characterized via haplotype, using two single nucleotide polymorphisms (SNPs). Ordered logit models were constructed to predict levels of depressive symptoms from 5-HTTLPR and stressors, comparing results of the most commonly applied statistical approaches (i.e., comparing allelic and genotypic models, and continuous and categorical predictors) used in the literature. All models were stratified by race/ethnicity. Overall, results show a main effect of recent stress for all ethnic groups, and mixed results for the variation in 5-HTTLPR × stress interaction, contingent upon statistical model used. Findings suggest there may be a differential effect of stressors and 5-HTTLPR on depressive symptoms by ethnicity, but further research is needed, particularly when using a haplotype to characterize variation in 5-HTTLPR in population-based sample with a diverse ethnic composition.

Factors associated with depression: sex differences between residents of Quilombo communities

INTRODUCTION: The Quilombola population is subject to numerous sources of social vulnerability, but few studies investigate their physical or mental health conditions. OBJECTIVES: To investigate the factors associated with depression in men and women, separately. METHODOLOGY: Cross-sectional population-based study with 764 randomly selected participants from five quilombo communities in Vitória da Conquista, Bahia, Brazil. The cutoff point for depression was ≥ 10 points, assessed by the Patient Health Questionnaire score (PHQ-9), and the presence of five or more symptoms. We estimated the prevalence ratio with 95% confidence intervals using Poisson regression models with robust estimators stratified by gender. RESULTS: Among men, factors associated with depression were previous diagnosis of chronic illnesses, poor/very poor health self-assessment, and poor access to health services. Among women, the associated factors were previous diagnosis of psychiatric disorders, poor/very poor health self-perception, history of tobacco smoking, and self-declaration of race as not black. CONCLUSION: Factors associated with depression differ between men and women and must be considered in interventions to fight depression within this population.

Differential susceptibility in longitudinal models of gene-environment interaction for adolescent depression

Although family support reliably predicts the development of adolescent depression and suicidal behaviors, relatively little is known about the interplay of family support with potential genetic factors. We tested the association of the 44 base pair polymorphism in the serotonin transporter linked promoter region gene (5-HTTLPR), family support (i.e., cohesion, communication, and warmth), and their interaction with self-reported depression symptoms and risk for suicide in 1,030 Caucasian adolescents and young adults from the National Longitudinal Study of Adolescent Health. High-quality family support predicted fewer symptoms of depression and reduced risk for suicidality. There was also a significant interaction between 5-HTTLPR and family support for boys and a marginally significant interaction for girls. Among boys with poor family support, youth with at least one short allele had more symptoms of depression and a higher risk for suicide attempts relative to boys homozygous for the long allele. However, in the presence of high family support, boys with the short allele had the fewest depression symptoms (but not suicide attempts). Results suggest that the short allele may increase reactivity to both negative and positive family influences in the development of depression. We discuss the potential role of interactive exchanges between family support and offspring genotype in the development of adolescent depression and suicidal behaviors.

Impact of variation in the BDNF gene on social stress sensitivity and the buffering impact of positive emotions: replication and extension of a gene-environment interaction

A previous study reported that social stress sensitivity is moderated by the brain-derived-neurotrophic-factor(Val66Met) (BDNF rs6265) genotype. Additionally, positive emotions partially neutralize this moderating effect. The current study aimed to: (i) replicate in a new independent sample of subjects with residual depressive symptoms the moderating effect of BDNF(Val66Met) genotype on social stress sensitivity, (ii) replicate the neutralizing impact of positive emotions, (iii) extend these analyses to other variations in the BDNF gene in the new independent sample and the original sample of non-depressed individuals. Previous findings were replicated in an experience sampling method (ESM) study. Negative Affect (NA) responses to social stress were stronger in "Val/Met" carriers of BDNF(Val66Met) compared to "Val/Val" carriers. Positive emotions neutralized the moderating effect of BDNF(Val66Met) genotype on social stress sensitivity in a dose-response fashion. Finally, two of four additional BDNF SNPs (rs11030101, rs2049046) showed similar moderating effects on social stress-sensitivity across both samples. The neutralizing effect of positive emotions on the moderating effects of these two additional SNPs was found in one sample. In conclusion, ESM has important advantages in gene-environment (GxE) research and may attribute to more consistent findings in future GxE research. This study shows how the impact of BDNF genetic variation on depressive symptoms may be explained by its impact on subtle daily life responses to social stress. Further, it shows that the generation of positive affect (PA) can buffer social stress sensitivity and partially undo the genetic susceptibility.

Children at risk for depression: memory biases, self-schemas, and genotypic variation

BACKGROUND

Daughters of depressed mothers are at increased risk for developing a depressive disorder. We know relatively little, however, about the specific factors that contribute to this elevated risk. The present study investigated the effects of familial risk for depression and the 5-HTTLPR and COMT Val158Met polymorphisms, which have been associated with risk for depression, on biases in endorsement of and memory for positive and negative adjectives.

METHODS

Following a negative mood induction, 60 girls between the ages of 10 and 14 who had recurrent depressed mothers (high risk for depression) and 91 age-matched daughters of never-disordered mothers (low risk for depression) completed a Self-Referent Encoding Task in which they decided whether negative and positive adjectives described them. Following the task they were asked to recall as many of the adjectives as they could.

RESULTS

Despite the absence of significant group differences in endorsement of positive or negative adjectives, high-risk girls with the COMT Val158Met Val/Val polymorphism recalled more positive (but not negative) words that they had endorsed than did high-risk girls who were homozygous for the Met allele. COMT was not associated with recall of valenced adjectives in low-risk girls. Across risk groups, 5-HTTLPR polymorphism was not associated with recall of valenced adjectives.

LIMITATIONS

Even with over 150 participants, there were relatively small numbers in some of the cells of this study, limiting its statistical power.

CONCLUSIONS

These results suggest that assessing the interaction of familial risk status and COMT polymorphism is important in understanding the development of depressive disorders.

Negative emotionality mediates the association of 5-HTTLPR genotype and depression in children with and without ADHD

The 44-base-pair polymorphism in the promoter region of the serotonin transporter gene (5-HTTLPR) has been implicated in the etiology of depression, but relatively little is known about potential mediators of this association. Although dimensions of temperament are likely to be proximal to the neurobiological and genetic factors underlying depression, studies have yet to formally evaluate temperament as a potential causal pathway. We examined individual differences in dimensions of temperament [negative emotionality (NE), prosociality (PRO), and daring (DA)] as potential mediators of 5-HTTLPR genotype and child depression. Using a multiple mediation framework, we tested the association of child 5-HTTLPR genotype and these dimensions of temperament with multi-informant ratings of child depression in a sample of 218 children with and without attention-deficit/hyperactivity disorder (ADHD). The long allele of 5-HTTLPR was associated with higher NE and lower PRO, but not DA. High NE mediated the association of 5-HTTLPR genotype and separate parent and teacher ratings of depression. ADHD status did not moderate the mediational role of NE for 5-HTTLPR and depression. Results suggest that NE may constitute a pathway between 5-HTTLPR and child depression. The role of genetic variation and temperament dimensions as intermediate traits in the development of depression is discussed.

Clinical implications of genetic variation in the serotonin transporter promoter region: a review

OBJECTIVE

To determine the state of the art in understanding the role of genetic variation in the serotonin transporter (5-HTT) promoter region (5-HTTLPR) in the development of a depressive episode and in its response to treatment.

DATA SOURCES

PubMed and Ovid were used to search for articles published prior to December 2007 utilizing the key words serotonin transporter, 5-HTT, 5-HTTLPR, serotonin transporter gene, and SLC6A4.

STUDY SELECTION

All studies were reviewed, but case reports and small case series were excluded.

DATA EXTRACTION

All relevant articles were read by at least 2 of the coauthors and notes regarding study design, measures, data analysis, and findings were later used to construct the review.

DATA SYNTHESIS

A common genetic variant, the short allele, in which 44 base pairs are missing from the promoter of SLC6A4, is associated with a greater risk for developing a major depressive disorder in patients following exposure to adversity. This association appears to be most important in the early stages of the depressive disorder. Additionally, the likelihood of a positive response to antidepressant treatment may be reduced in these patients in terms of delayed response, greater adverse event load, or, in bipolar patients, mania induction and rapid cycling.

CONCLUSIONS

Selected genetic testing of patients with a recent history of significant adversity may be a reasonable tool that can enlighten treatment options and the course of illness. Ongoing work with the short allele of 5-HTT may also inform clinical guidelines of long-term treatment with antidepressants.

The serotonin transporter gene polymorphism (5HTTLPR) moderates the effect of adolescent environmental conditions on self-esteem in young adulthood: a structural equation modeling approach

Here we examine the effects of both self-reported and independent observer-reported environmental risk indices, the serotonin transporter gene promoter (5HTTLPR) polymorphism, and their interaction on self-esteem. This trait was assessed during early and mid adolescence (mean age=14 and 16.5, respectively) and young adulthood (mean age=21.8) in a prospective cohort of 1214 unrelated participants in the Longitudinal Study of Adolescent Health (Add Health). Using structural equation modeling we identified a gene-environment (G×E) interaction using observer-report but not self-report measures of environmental stress exposure during adolescence: 5HTTLPR genotype and observer-reports of home and neighborhood quality (HNQ) during adolescence interacted to predict self-esteem levels in young adulthood (p<.004). Carriers of the s allele who lived in poor HNQ conditions during adolescence reported lower self-esteem in young adulthood than those with a good HNQ during adolescence. In contrast, among individuals with the l/l genotype, adolescent HNQ did not predict adulthood self-esteem. Genes may moderate the effect of adolescent environmental conditions on adulthood self-esteem.

Maternal depression and child and adolescent depression symptoms: an exploratory test for moderation by CRHR1, FKBP5 and NR3C1 gene variants

This study investigated moderation of the association between recurrent maternal depression and offspring depression symptoms by a selection of biologically relevant gene variants. 271 children/adolescents (aged 9.00 to 16.00 years) whose mothers had experienced at least two episodes of DSM-IV major depression and 165 controls (aged 12.25 to 16.67 years) drawn from a population-based twin register were used. Seven single nucleotide polymorphisms (SNPs) from three genes were genotyped in children. The genes were the Corticotropin Receptor Type 1 gene (CRHR1), the gene coding for the FK506 binding protein 5 (FKBP5) and the Glucocorticoid receptor gene (NR3c1) along with a haplotype formed by the SNPs in CRHR1. A significant association was found between recurrent maternal depression and depression symptoms in offspring. None of the SNPs were associated with offspring depression symptoms and associations did not differ according to the presence of recurrent maternal depression. However, caution is required due to a relatively small sample size.

The serotonin transporter promoter polymorphism and childhood positive and negative emotionality

Association studies of the serotonin transporter promoter polymorphism (5-HTTLPR) and negative emotionality (NE) are inconclusive. However, emerging evidence suggests that the association between this polymorphism and NE may be influenced by levels of another temperament trait, positive emotionality (PE). Therefore, this study examined whether the association between the 5-HTTLPR and NE was moderated by PE. A community sample of 413 three-year-old children completed a standardized battery of laboratory tasks designed to tap temperamental emotionality. Children were also genotyped for the 5-HTTLPR. No direct association between 5-HTTLPR genotype and NE was found. However, the interaction of child PE and NE predicted 5-HTTLPR genotype. Furthermore, children with a short allele who were also low in PE had significantly greater NE than children without a short allele or children with high PE. Our findings suggest that the short allele of the 5-HTTLPR is associated with NE only in the context of low PE. Inconsistent links between NE and this gene in previous research may stem from the failure to consider other temperament traits that moderate associations.

Low autonomic arousal as vulnerability to externalising behaviour in infants with hostile mothers

Maternal psychopathology and the child's autonomic nervous system functioning are risk factors for aggressive behaviour later in life. While research has shown that maternal psychopathology already affects young children, less is known about the association between autonomic functioning and aggressive behaviour in young children. In addition, maternal psychopathology and autonomic nervous system functioning may interact to determine the risk of aggressive behaviour. In a sample of 375 infants and their mothers, maternal psychiatric symptoms were assessed with the Brief Symptom Inventory and toddler aggressive behaviour with the Child Behaviour Checklist. Infant heart rate was recorded at 14 months. Maternal psychiatric problems, including hostility and depression, were associated with toddler aggressive behaviour. Maternal psychiatric problems interacted with mean heart rate (P=0.01) and HF variability (P=0.03) in their effect on toddler aggressive behaviour. Mothers with high psychiatric problems, in particular, high hostility, were more likely to have toddlers with high aggressive behaviour. Moreover, in the presence of maternal risk factors, low autonomic arousal renders children particularly susceptible to aggressive behaviour.

Genetics of childhood and adolescent depression: insights into etiological heterogeneity and challenges for future genomic research

There is heterogeneity between depression in childhood, adolescence and adulthood in terms of the gender composition of affected cases, prevalence, rates of recurrence and risk factors. This raises complex questions for refining the phenotype for molecular genetic studies of depression and the selection of appropriate proband groups. This article aims to provide a review of issues arising from family, twin and adoption studies of relevance to molecular genetic studies, and to summarize molecular genetic findings on childhood/adolescent depression. While retrospective studies of adults suggest greater familial aggregation among those with an earlier age of onset, prospective studies do not confirm this association. In fact, taken together, evidence from family and twin studies suggests that prepubertal depression is more strongly associated with psychosocial adversity, is less heritable and shows lower levels of continuity with adult depression than either adolescent or adult depression. Adolescent depressive symptoms and disorder show similar levels of heritability to depression in adult life, although there is only one twin study of adolescent depressive disorder, and heritability estimates of depressive symptoms vary widely between studies. This variability in heritability estimates is partly attributable to age and informant effects. Adoption studies and other intergenerational transmission designs show that the transmission of depression between parents and children involves genetic and environmental processes, with converging evidence that environmental processes are most important. Molecular genetic studies of childhood/adolescent depression have to date used a candidate gene approach and focused on genes already examined in adult studies. Prospective longitudinal studies of community and high-risk samples are needed to clarify issues of etiological heterogeneity in depression, and these should in turn inform the planning of molecular genetic studies.

Interaction of chronic stress with serotonin transporter and catechol-O-methyltransferase polymorphisms in predicting youth depression

BACKGROUND

Investigations of gene-environment interaction (GxE) in depression have implicated a polymorphism in the promoter region of the serotonin transporter gene (5-HTTLPR) as a moderator of the stress-depression relationship. However, recent evidence for 5-HTTLPR GxE in depression has been inconsistent. This study examined the moderating effect of the val158met polymorphism in the catechol-O-methyltransferase (COMT) gene on the strength of 5-HTTLPR GxE.

METHODS

A community sample of youth (n=384) was genotyped for 5-HTTLPR and COMT. A multi-method, multi-informant index of chronic family stress was derived from interviews and questionnaires administered at youth age 15. GxGxE was examined in relation to depression diagnoses between ages 15 and 20 and depressive symptoms at age 20.

RESULTS

Significant three-way interactions were observed for both depressive symptoms and diagnoses, such that 5-HTTLPR GxE occurred only in the context of COMT val158 allele homozygosity. For val158 homozygotes, the 5-HTTLPR LL genotype exerted a protective effect in the face of stress. No genetic main effect or two-way GxE was found for 5-HTTLPR.

CONCLUSIONS

Inconsistent 5-HTTLPR GxE findings to date may be partly attributable to unmeasured epistatic effects between 5-HTTLPR and COMT val158met. Identifying the conditions under which 5-HTTLPR GxE is most likely to operate may allow depression prevention and treatment efforts to target youth at highest risk.

How ideology shapes the evidence and the policy: what do we know about cannabis use and what should we do?

In the United Kingdom, as in many places, cannabis use is considered substantially within a criminal justice rather than a public health paradigm with prevention policy embodied in the Misuse of Drugs Act. In 2002 the maximum custodial sentence tariff for cannabis possession under the Act was reduced from 5 to 2 years. Vigorous and vociferous public debate followed this decision, centred principally on the question of whether cannabis use caused schizophrenia. It was suggested that new and compelling evidence supporting this hypothesis had emerged since the re-classification decision was made, meaning that the decision should be reconsidered. The re-classification decision was reversed in 2008. We consider whether the strength of evidence on the psychological harms of cannabis has changed substantially and discuss the factors that may have influenced recent public discourse and policy decisions. We also consider evidence for other harms of cannabis use and public health implications of preventing cannabis use. We conclude that the strongest evidence of a possible causal relation between cannabis use and schizophrenia emerged more than 20 years ago and that the strength of more recent evidence may have been overstated--for a number of possible reasons. We also conclude that cannabis use is almost certainly harmful, mainly because of its intimate relation to tobacco use. The most rational policy on cannabis from a public health perspective would seem to be one able to achieve the benefit of reduced use in the population while minimizing social and other costs of the policy itself. Prohibition, whatever the sentence tariff associated with it, seems unlikely to fulfil these criteria.

Chronic and acute stress, gender, and serotonin transporter gene-environment interactions predicting depression symptoms in youth

BACKGROUND

Many recent studies of serotonin transporter gene by environment effects predicting depression have used stress assessments with undefined or poor psychometric methods, possibly contributing to wide variation in findings. The present study attempted to distinguish between effects of acute and chronic stress to predict depressive symptoms at age 20 among 346 youth varying in polymorphisms of the 5HTT gene who had been assessed at ages 15 and 20.

METHODS

Interview measures assessed major acute life events between 15 and 19, and multiple interviews and questionnaires with youths and their parents at youth age 15 provided an index of chronic family stress. Lg alleles were reclassified as S.

RESULTS

Chronic family stress at age 15 predicted higher depression scores at 20 among those with one or two S alleles, and the effects of genetic moderation were significant only for females. Gene-environment interactions with acute stress were nonsignificant.

CONCLUSIONS

Careful measurement and separation of the effects of chronic and acute stress, and gender, are encouraged in the study of mechanisms of the stress-depression association.

The genetics of bipolar disorder

Bipolar disorder is a mood disorder characterized by impairing episodes of mania and depression. Twin studies have established that bipolar disorder is among the most heritable of medical disorders and efforts to identify specific susceptibility genes have intensified over the past two decades. The search for genes influencing bipolar disorder has been complicated by a paucity of animal models, limited understanding of pathogenesis, and the genetic and phenotypic complexity of the syndrome. Linkage studies have implicated several chromosomal regions as harboring relevant genes, but results have been inconsistent. It is now widely accepted that the genetic liability to bipolar disorder reflects the action of many genes of individually small effect, a scenario for which linkage studies are poorly suited. Thus, association studies, which are more powerful for the detection of modest effect loci, have become the focus of gene-finding research. A large number of candidate genes, including biological candidates derived from hypotheses about the pathogenesis of the disorder and positional candidates derived from linkage and cytogenetic studies, have been evaluated. Several of these genes have been associated with the disorder in independent studies (including BDNF, DAOA, DISC1, GRIK4, SLC6A4, and TPH2), but none has been established. The clinical heterogeneity of bipolar disorder and its phenotypic and genetic overlap with other disorders (especially schizophrenia, schizoaffective disorder, and major depressive disorder) have raised questions about the optimal phenotype definition for genetic studies. Nevertheless, genomewide association analysis, which has successfully identified susceptibility genes for a variety of complex disorders, has begun to implicate specific genes for bipolar disorder (DGKH, CACNA1C, ANK3). The polygenicity of the disorder means that very large samples will be needed to detect the modest effect loci that likely contribute to bipolar disorder. Detailed genetic dissection of the disorder may provide novel targets (both pharmacologic and psychosocial) for intervention.

Vulnerability genes or plasticity genes?

The classic diathesis-stress framework, which views some individuals as particularly vulnerable to adversity, informs virtually all psychiatric research on behavior-gene-environment (G x E) interaction. An alternative framework of 'differential susceptibility' is proposed, one which regards those most susceptible to adversity because of their genetic make up as simultaneously most likely to benefit from supportive or enriching experiences-or even just the absence of adversity. Recent G x E findings consistent with this perspective and involving monoamine oxidase-A, 5-HTTLPR (5-hydroxytryptamine-linked polymorphic region polymorphism) and dopamine receptor D4 (DRD4) are reviewed for illustrative purposes. Results considered suggest that putative 'vulnerability genes' or 'risk alleles' might, at times, be more appropriately conceptualized as 'plasticity genes', because they seem to make individuals more susceptible to environmental influences-for better and for worse.

Interaction between the serotonin transporter gene (5-HTTLPR), stressful life events, and risk of depression: a meta-analysis

CONTEXT

Substantial resources are being devoted to identify candidate genes for complex mental and behavioral disorders through inclusion of environmental exposures following the report of an interaction between the serotonin transporter linked polymorphic region (5-HTTLPR) and stressful life events on an increased risk of major depression.

OBJECTIVE

To conduct a meta-analysis of the interaction between the serotonin transporter gene and stressful life events on depression using both published data and individual-level original data.

DATA SOURCES

Search of PubMed, EMBASE, and PsycINFO databases through March 2009 yielded 26 studies of which 14 met criteria for the meta-analysis.

STUDY SELECTION

Criteria for studies for the meta-analyses included published data on the association between 5-HTTLPR genotype (SS, SL, or LL), number of stressful life events (0, 1, 2, > or = 3) or equivalent, and a categorical measure of depression defined by the Diagnostic and Statistical Manual of Mental Disorders (Fourth Edition) or the International Statistical Classification of Diseases, 10th Revision (ICD-10) or use of a cut point to define depression from standardized rating scales. To maximize our ability to use a common framework for variable definition, we also requested original data from all studies published prior to 2008 that met inclusion criteria. Of the 14 studies included in the meta-analysis, 10 were also included in a second sex-specific meta-analysis of original individual-level data.

DATA EXTRACTION

Logistic regression was used to estimate the effects of the number of short alleles at 5-HTTLPR, the number of stressful life events, and their interaction on depression. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated separately for each study and then weighted averages of the individual estimates were obtained using random-effects meta-analysis. Both sex-combined and sex-specific meta-analyses were conducted. Of a total of 14,250 participants, 1769 were classified as having depression; 12,481 as not having depression.

RESULTS

In the meta-analysis of published data, the number of stressful life events was significantly associated with depression (OR, 1.41; 95% CI,1.25-1.57). No association was found between 5-HTTLPR genotype and depression in any of the individual studies nor in the weighted average (OR, 1.05; 95% CI, 0.98-1.13) and no interaction effect between genotype and stressful life events on depression was observed (OR, 1.01; 95% CI, 0.94-1.10). Comparable results were found in the sex-specific meta-analysis of individual-level data.

CONCLUSION

This meta-analysis yielded no evidence that the serotonin transporter genotype alone or in interaction with stressful life events is associated with an elevated risk of depression in men alone, women alone, or in both sexes combined.

The influence of family structure, the TPH2 G-703T and the 5-HTTLPR serotonergic genes upon affective problems in children aged 10-14 years

BACKGROUND

Both genetic and psychosocial risk factors influence the risk for depression in development. While the impacts of family structure and of serotonergic polymorphisms upon individual differences for affective problems have been investigated separately, they have never been considered together in a gene-environment interplay perspective.

METHODS

We examined the effects of family structure and two serotonergic polymorphisms (the TPH2 G-703T and the 5-HTTLPR) upon depressive symptoms assessed by the new CBCL/6-18 DSM-oriented Affective Problems scale in a general population sample of 607 Italian children aged 10-14 years.

RESULTS

Belonging to 'one-parent' families, the TPH2 G-703T 'G variant', and the 5-HTTLPR 'short' alleles were associated - both alone and in apparent gene-by-environment interaction - with higher Affective Problems scores. As predicted by quantitative genetics theory, both polymorphisms contributed with a small effect size, while 'family structure' had a moderate effect size.

CONCLUSIONS

A putative hazard factor impinging on individual risk at the family-wide level, namely family structure, appears to act interactively with two pivotal serotonergic genes in heightening risk for Affective Problems. Although it remains to be demonstrated that belonging to a one- rather than a two-parent family has true environmental causal effects on Affective Problems, these data may contribute to identify/prevent risk for depression in childhood.

Depression and the serotonin transporter 5-HTTLPR polymorphism: a review and a hypothesis concerning gene-environment interaction

Studies of the interaction of the serotonin transporter genotype and environment upon adult depression (G x E) have suggested a role for both childhood maltreatment and stressful life events. This paper deals with two main issues. First, do both contribute? Evidence that G x E with childhood maltreatment plays a role is much stronger than that for G x E with life events occurring close to onset, although that for G x E with life events occurring over a 5-year period before the presence of the recorded depression is stronger. However, non-genetic research shows that life events occurring so long before onset as 5 years have little or no relationship with adult depression once childhood maltreatment is taken into account, suggesting they serve as a marker for childhood maltreatment rather than making a direct contribution to G x E. Second, genetic research has dealt only with the presence of depression and taking account of course may radically change ideas about the point at which G x E occurs. Two findings from non-genetic research concerning childhood maltreatment are relevant. Childhood maltreatment is associated with a particularly high risk of an adult onset of depression taking a chronic course (i.e. lasting 12 months or more). Moreover such maltreatment makes a substantial direct contribution - i.e. its link with course is independent of all other childhood and adult risk factors. This is consistent with early changes in brain function associated with the polymorphism in the context of childhood maltreatment explaining the link of such maltreatment with adult chronic episodes. It also follows that restricting analysis to such episodes would increase current estimates of G x E.

Analysis of a functional serotonin transporter promoter polymorphism in psoriasis vulgaris

Serotonin is a monoamine acting as a neuromediator in the central and peripheral nervous system. Recently, serotonin has also been shown to influence T- and B-cell function. The serotonin transporter is central in the regulation of the serotonergic system and widely expressed on cells of the immune system. A functional length polymorphism in the promoter of the serotonin transporter gene (5-HTTLPR) has been implicated in the genetic background of depression. Psoriasis is a complex disease with a polygenetic inheritance. In light of the role of T-cell mediated inflammation in psoriasis and the increased prevalence of depression in psoriatic patients, we analyzed the 5-HTTLPR polymorphism in 309 patients with psoriasis vulgaris and 315 healthy control individuals. No significant differences in genotype distribution and allele frequencies were found. There was also no difference in the score of the Hamilton Rating Scale for Depression in patients with psoriasis (n = 137) characterized by carriage of different 5-HTTLPR genotypes. These findings argue against a major contribution of the 5-HTTLPR polymorphism to psoriasis susceptibility and the occurrence of depressive symptoms among psoriatic patients.

An examination of the association between the 5-HTT promoter region polymorphism and depressogenic attributional styles in childhood

Although a vast literature examining the role of attributional styles in depression has accumulated, the origins of such cognitions remain poorly understood. Investigators are increasingly interested in whether cognitive vulnerability to depression is linked to genetic variation. As a preliminary test of this hypothesis, we examined whether the serotonin transporter promoter polymorphism (5-HTTLPR) was associated with attributional styles in children. Thirty-eight children completed a self-report measure of attributional styles, the Child Attributional Style Questionnaire-Revised (CASQ-R). Children were also genotyped for the 5-HTTLPR polymorphism, including the single nucleotide polymorphism (SNP) rs25531 in the long allele of the 5-HTTLPR. The short alleles of the 5-HTTLPR and their putative functional equivalents were associated with increased levels of depressogenic attributions for negative events, as measured by the CASQ-R, lending support to the role of 5-HTTLPR polymorphisms in cognitive vulnerability to depression.

Gene-Environment Interactions in Depression Research

Recent studies on life stress, depression, and polymorphisms in the promoter region of the serotonin transporter gene (5-HTTLPR) are characterized by powerful genetic techniques, but are also characterized by unconventional and inconsistent approaches to assessing life stress. The present review addresses this problem by critically evaluating this rapidly growing literature with regard to the concepts and procedures employed to assess life stress and the research designs used to test causal associations. The existing body of evidence is seriously compromised by the predominance of ad hoc approaches for measuring life stress and by a lack of attention to key issues concerning research design. Principles and procedures for more refined and rigorous stress measurement are outlined. Improved guidelines are needed to direct future research on interactive effects of life stress and genes in psychopathology, pathophysiological processes, and disease.

Early-emerging cognitive vulnerability to depression and the serotonin transporter promoter region polymorphism

BACKGROUND

Serotonin transporter promoter (5-HTTLPR) genotype appears to increase risk for depression in the context of stressful life events. However, the effects of this genotype on measures of stress sensitivity are poorly understood. Therefore, this study examined whether 5-HTTLPR genotype was associated with negative information processing biases in early childhood.

METHOD

Thirty-nine unselected seven-year-old children completed a negative mood induction procedure and a Self-Referent Encoding Task designed to measure positive and negative schematic processing. Children were also genotyped for the 5-HTTLPR gene.

RESULTS

Children who were homozygous for the short allele of the 5-HTTLPR gene showed greater negative schematic processing following a negative mood prime than those with other genotypes. 5-HTTLPR genotype was not significantly associated with positive schematic processing.

LIMITATIONS

The sample size for this study was small. We did not analyze more recently reported variants of the 5-HTTLPR long alleles.

CONCLUSIONS

5-HTTLPR genotype is associated with negative information processing styles following a negative mood prime in a non-clinical sample of young children. Such cognitive styles are thought to be activated in response to stressful life events, leading to depressive symptoms; thus, cognitive styles may index the "stress-sensitivity" conferred by this genotype.

The contribution of gene-environment interaction to psychopathology

The study of gene-environment interaction (G x E) constitutes an area of significant social and clinical significance. Different types of research study designs are being used to investigate the contribution of G x E to psychopathology, although the term G x E has also been used and interpreted in different ways. Despite mixed evidence that G x E contributes to psychopathology, some promising and consistent findings are emerging. Evidence is reviewed in relation to depression, antisocial behavior, schizophrenia, and attention-deficit/hyperactivity disorder. Although findings from various research designs have different meaning, interestingly much of the evidence with regard to the contribution of G x E that has arisen from twin and adoption studies has been for antisocial behavior and depression. It is for these same forms of psychopathology that molecular genetic evidence of G x E has also been most convincing. Finally, current and anticipated methodological challenges and implications for future research in this area are considered.

Late neurodevelopmental effects of early exposures to chemical contaminants: reducing uncertainty in epidemiological studies

Early exposures to environmental chemicals are reliably associated with late neurotoxicities in children. However, substantial scatter of observations exists around the estimated dose-effect relationships. This variability has many potential sources, one of which is interindividual differences in susceptibility. Such differences imply that the long-term impacts of exposure will not the same for all individuals, but will vary depending on a variety of factors that might either aggravate or mitigate contaminant effects. These include co-exposures, genetic polymorphisms and characteristics of the social environment. The context dependence of contaminant effects has implications both for study designs and analytical approaches. In addition, a systems approach to understanding the associations among contaminant exposures, covariates and health outcomes is necessary.

Stressful life events and depressive problems in early adolescent boys and girls: the influence of parental depression, temperament and family environment

BACKGROUND

Stressful life events increase the probability of depressive problems in early adolescence. Several genetic and environmental risk factors may change individual sensitivity to the depressogenic effect of these events. We examined modification by parental depression and gender, and mediation of the former by temperament and family environment.

METHODS

Data were collected as part of a longitudinal cohort study of (pre)adolescents (n = 2127). During the first assessment wave at approximately age 11, we assessed parental depression, family functioning, perceived parenting behaviours, and temperamental frustration and fearfulness. At the second wave, about two and a half years later, stressful life events between the first and second assessment were assessed. Depressive problems were measured at both waves.

RESULTS

Adolescents with parents who had a (lifetime) depressive episode were more sensitive to the depressogenic effect of stressful events than adolescents without depressed parents. Furthermore, girls are more sensitive to these effects than boys. The modifying effect of parental depression was not mediated by temperament, family functioning and perceived parenting.

LIMITATIONS

Life events were assessed without consideration of contextual information. Depressive problems were measured by questionnaires that did not directly represent DSM-IV criteria. The measure of parental depression was unspecific regarding severity and timing of depressive episodes.

CONCLUSION

The results suggest that gender and parental depression are associated with increased sensitivity to depression after experiencing stressful life events during adolescence.

Bad nature, bad nurture, and testimony regarding MAOA and SLC6A4 genotyping at murder trials

Recent research-in which subjects were studied longitudinally from childhood until adulthood-has started to clarify how a child's environment and genetic makeup interact to create a violent adolescent or adult. For example, male subjects who were born with a particular allele of the monoamine oxidase A gene and also were maltreated as children had a much greater likelihood of manifesting violent antisocial behavior as adolescents and adults. Also, individuals who were born with particular alleles of the serotonin transporter gene and also experienced multiple stressful life events were more likely to manifest serious depression and suicidality. This research raises the question of whether testimony regarding a defendant's genotype, exposure to child maltreatment, and experience of unusual stress is appropriate to present during the guilt or penalty phases of criminal trials, especially when capital punishment is a consideration. The authors present their experience in genotyping criminal defendants and presenting genetic information at criminal trials.

The risk for depression conferred by stressful life events is modified by variation at the serotonin transporter 5HTTLPR genotype: evidence from the Spanish PREDICT-Gene cohort

We report results from the PREDICT-Gene case-control study nested in a prospective cohort designed to identify predictors of the onset of depression among adult primary-care attendees. We tested the potential gene-by-environment interaction between 5HTTLPR genotype at the serotonin transporter gene and previous exposure to threatening life events (TLEs) in depression. A total of 737 consecutively recruited participants were genotyped. Additional information was gathered on exposure to TLEs over a 6-month period, socio-demographic data and family history of psychological problems among first-degree relatives. Diagnoses of depression were ascertained using the Composite International Diagnostic Interview (CIDI) by trained interviewers. Two different depressive outcomes were used (ICD-10 depressive episode and ICD-10 severe depressive episode). Both the s/s genotype and exposure to increasing number of TLEs were significantly associated with depression. Moreover, the 5HTTLPR s/s genotype significantly modified the risk conferred by TLEs for both depressive outcomes. Thus, s/s homozygous participants required minimal exposure to TLE (1 TLE) to acquire a level of risk for depression that was only found among l/s or l/l individuals after significantly higher exposure to TLEs (two or more TLEs). The interaction was more apparent when applied to the diagnosis of ICD-10 severe depressive episode and after adjusting for gender, age and family history of psychological problems. Likelihood ratios tests for the interaction were statistically significant for both depressive outcomes (ICD-10 depressive episode: LR X(2)=4.7, P=0.09 (crude), LR-X(2)=6.4, P=0.04 (adjusted); ICD-10 severe depressive episode: LR X(2)=6.9, P=0.032 (crude), LR-X(2)=8.1, P=0.017 (adjusted)).

Epidemiology of subtypes of depression

OBJECTIVE

There is a general clinical impression that depression differs qualitatively from non-depressive conditions, and that it can be identified as a categorical entity. In contrast, epidemiological studies support the view that depression is dynamic in nature and develops on a continuous scale. The present article reviews selected epidemiological studies of depressive subtypes.

METHOD

A selective review.

RESULTS

Prior studies have found no clear differences in clinical presentation or long-term outcome between patients with melancholic and with neurotic/reactive depression. In addition, recent studies suggest that there is no clear demarcation between mild, moderate, and severe depression, pointing toward a continuity rather than categories of illness. For the individual patient, depressive symptoms seem to change over time, fulfilling criteria for major depression, minor depression, dysthymia, and subsyndromal states; the association between stressful life events and depression appears to diminish with the number of depressive episodes. Finally, recent genetic findings are congruent with a model indicating that the majority of depressions develop in the interplay between genes and stressful experiences, whereas 'reactive' depressions and 'endogenous' depressions apparently exist at a lower prevalence.

CONCLUSION

Further longitudinal, analytical, and genetic epidemiologic studies are needed to reveal which conditions are mild and transient, and which may be precursors of more severe and substantial illness such as melancholia.

The genetics of bipolar affective disorder

PURPOSE OF REVIEW

Molecular genetic studies of bipolar affective disorder are beginning to show some positive and reproducible findings. The most relevant of these will be reviewed.

RECENT FINDINGS

Obtaining consistent findings from whole genome scans has been hampered by small sample sizes and phenotypic heterogeneity. Recently, there have been concerted efforts to overcome these problems by combining data for meta-analysis. What has become increasingly clear is that several regions that are likely to contain genes contributing to bipolar affective disorder are also relevant to schizophrenia, a finding supported by recent twin data. Studies to date have implicated the D-amino acid oxidase activator complex (also known as G72/G30), disrupted in schizophrenia-1 and neuregulin, and have pointed to several promising linkage regions in which the genes have not yet been identified. In addition, there is some evidence to support the involvement of genetic variants in catechol-o-methyl transferase and brain-derived neurotrophic factor in the aetiology of bipolar affective disorder.

SUMMARY

Molecular genetic research in bipolar affective disorder may lead to the development of new diagnostic paradigms for classifying the psychoses and affective states. In addition, determining the functional significance of the susceptibility genes will pave the way for enhanced diagnostic accuracy and improved treatments.

The 5-HTTLPR s/s genotype at the serotonin transporter gene (SLC6A4) increases the risk for depression in a large cohort of primary care attendees: the PREDICT-gene study

Previous reports and meta-analyses have yielded inconclusive results as to whether the s/s genotype at the 5-HTTLPR serotonin transporter polymorphism confers increased risk for depression. We tested the association between s/s genotype and depression in a large cohort (n = 737) of Spanish primary care consecutive attendees participating in a European study on predictors for depression in primary care (PREDICT study). Participants were administered the Composite International Diagnostic Interview (CIDI) depression subscale allowing diagnoses using ICD-10 criteria for depressive episodes. Participants were genotyped to establish 5HTTLPR genotype. Both univariable and multivariable associations between the s/s genotype and depression were tested twice using two different depressive outcomes (ICD-10 depressive episode and ICD-10 severe depressive episode). We found an association between the s/s genotype and both depressive outcomes that was independent of age, sex, family history of psychological problems among first degree relatives and presence of comorbid generalized anxiety disorder. When comparing s/s homozygous versus the rest, the adjusted odds ratio for any ICD-10 depressive episode and for severe ICD-10 depressive episode were 1.50 (95% CI: 1.0-2.2; P = 0.045) and 1.79 (95% CI: 1.1-2.8; P = 0.016), respectively. The association was significantly stronger with increasing severity of depression (chi2 for linear association=6.1; P = 0.013) suggesting a dose-dependent relationship. Our results are consistent with previous reports suggesting a small but independent effect by the s/s 5-HTTLPR genotype increasing the risk for depression.

Genetic counselling for psychiatric disorders

Family, adoption and twin studies demonstrate that many adult psychiatric disorders, including schizophrenia, major depression and bipolar disorder, have a clear genetic component. The aetiology of psychiatric disorders is a complex combination of both genetic and environmental components. While potential susceptibility genes for psychiatric disorders have been identified, interaction with the environment is a crucial component in disease development. Pharmacogenetics and genetic testing have the potential to play key roles in the future of clinical psychiatry. At present, an increased risk of psychiatric disorders can be identified through a detailed family history. The empirical risk of developing a disorder has been determined for many psychiatric disorders and can be used as a general guide. Genetic counselling can extend and enhance patient care by providing information to patients about the complexities of inheriting psychiatric disorders and the associated risks of recurrence. The genetic counselling process can facilitate informed decision making, alleviate misconceptions and reduce stigma through an improved understanding of the genetic cause of psychiatric disorders, and offer support to patients and their families.