Research review: gene-environment interaction research in youth depression - a systematic review with recommendations for future research

Genome-wide polygenic scoring for a 14-year long-term average depression phenotype

BACKGROUND

Despite moderate heritability estimates for depression-related phenotypes, few robust genetic predictors have been identified. Potential explanations for this discrepancy include the use of phenotypic measures taken from a single time point, rather than integrating information over longer time periods via multiple assessments, and the possibility that genetic risk is shaped by multiple loci with small effects.

METHODS

We developed a 14-year long-term average depression measure based on 14 years of follow-up in the Nurses' Health Study (NHS; N = 6989 women). We estimated polygenic scores (PS) with internal whole-genome scoring (NHS-GWAS-PS). We also constructed PS by applying two external PS weighting algorithms from independent samples, one previously shown to predict depression (GAIN-MDD-PS) and another from the largest genome-wide analysis currently available (PGC-MDD-PS). We assessed the association of all three PS with our long-term average depression phenotype using linear, logistic, and quantile regressions.

RESULTS

In this study, the three PS approaches explained at most 0.2% of variance in the long-term average phenotype. Quantile regressions indicated PS had larger impacts at higher quantiles of depressive symptoms. Quantile regression coefficients at the 75th percentile were at least 40% larger than at the 25th percentile in all three polygenic scoring algorithms. The interquartile range comparison suggested the effects of PS significantly differed at the 25th and 75th percentiles of the long-term depressive phenotype for the PGC-MDD-PS (P = 0.03), and this difference also reached borderline statistical significance for the GAIN-MDD-PS (P = 0.05).

CONCLUSIONS

Integrating multiple phenotype assessments spanning 14 years and applying different polygenic scoring approaches did not substantially improve genetic prediction of depression. Quantile regressions suggested the effects of PS may be largest at high quantiles of depressive symptom scores, presumably among people with additional, unobserved sources of vulnerability to depression.

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.

Interaction between genetic variants and exposure to Hurricane Katrina on post-traumatic stress and post-traumatic growth: a prospective analysis of low income adults

BACKGROUND

There is considerable variation in psychological reactions to natural disasters, with responses ranging from relatively mild and transitory symptoms to severe and persistent posttraumatic stress (PTS). Some survivors also report post-traumatic growth (PTG), or positive psychological changes due to the experience and processing of the disaster and its aftermath. Gene-environment interaction (GxE) studies could offer new insight into the factors underlying variability in post-disaster psychological responses. However, few studies have explored GxE in a disaster context.

METHODS

We examined whether ten common variants in seven genes (BDNF, CACNA1C, CRHR1, FKBP5, OXTR, RGS2, SLC6A4) modified associations between Hurricane Katrina exposure and PTS and PTG. Data were from a prospective study of 205 low-income non-Hispanic Black parents residing in New Orleans prior to and following Hurricane Katrina.

RESULTS

We found a significant association (after correction) between RGS2 (rs4606; p=0.0044) and PTG, which was mainly driven by a cross-over GxE (p=0.006), rather than a main genetic effect (p=0.071). The G (minor allele) was associated with lower PTG scores for low levels of Hurricane exposure and higher PTG scores for moderate and high levels of exposure. We also found a nominally significant association between variation in FKBP5 (rs1306780, p=0.0113) and PTG, though this result did not survive correction for multiple testing.

LIMITATIONS

Although the inclusion of low-income non-Hispanic Black parents allowed us to examine GxE among a highly vulnerable group, our findings may not generalize to other populations or groups experiencing other natural disasters. Moreover, not all participants invited to participate in the genetic study provided saliva.

CONCLUSIONS

To our knowledge, this is the first study to identify GxE in the context of post-traumatic growth. Future studies are needed to clarify the role of GxE in PTS and PTG and post-disaster psychological responses, especially among vulnerable populations.

Ethics in prevention science involving genetic testing

The Human Genome Project and rapid technological advances in genomics have begun to enrich prevention science's contributions to understanding the role of genetic factors in the etiology, onset and escalation of mental disorders, allowing for more precise descriptions of the interplay between genetic and non-genetic influences. Understanding of ethical challenges associated with the integration of genetic data into prevention science has not kept pace with the rapid increase in the collection and storage of genetic data and dissemination of research results. This article discusses ethical issues associated with (1) decisions to withhold or disclose personal genetic information to participants; (2) implications of recruitment and data collection methods that may reveal genetic information of family members; and the (3) nature and timing of informed consent. These issues are presented within the contexts of adult and pediatric research, longitudinal studies, and use of biobanks for storage of genetic materials. Recommendations for research ethics decision-making are provided. The article concludes with a section on justice and research burdens and the unique ethical responsibilities of prevention scientists to ensure the new genomic science protects the informational rights of participants, their families and communities.

Gene-environment interactions in genome-wide association studies: current approaches and new directions

BACKGROUND

Complex psychiatric traits have long been thought to be the result of a combination of genetic and environmental factors, and gene-environment interactions are thought to play a crucial role in behavioral phenotypes and the susceptibility and progression of psychiatric disorders. Candidate gene studies to investigate hypothesized gene-environment interactions are now fairly common in human genetic research, and with the shift toward genome-wide association studies, genome-wide gene-environment interaction studies are beginning to emerge.

METHODS

We summarize the basic ideas behind gene-environment interaction, and provide an overview of possible study designs and traditional analysis methods in the context of genome-wide analysis. We then discuss novel approaches beyond the traditional strategy of analyzing the interaction between the environmental factor and each polymorphism individually.

RESULTS

Two-step filtering approaches that reduce the number of polymorphisms tested for interactions can substantially increase the power of genome-wide gene-environment studies. New analytical methods including data-mining approaches, and gene-level and pathway-level analyses, also have the capacity to improve our understanding of how complex genetic and environmental factors interact to influence psychologic and psychiatric traits. Such methods, however, have not yet been utilized much in behavioral and mental health research.

CONCLUSIONS

Although methods to investigate gene-environment interactions are available, there is a need for further development and extension of these methods to identify gene-environment interactions in the context of genome-wide association studies. These novel approaches need to be applied in studies of psychology and psychiatry.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Association between major depressive disorder and the norepinephrine transporter polymorphisms T-182C and G1287A: a meta-analysis

BACKGROUND

Previous studies have implicated norepinephrine transporter (NET) gene polymorphisms in the etiology of major depressive disorder (MDD). Recently, two single nucleotide NET polymorphisms, T-182C (rs2242446) in the promoter region and G1287A (rs5569) in exon 9, were found to be associated with MDD in different populations. However, inconsistent and inconclusive results have also been obtained.

METHODS

In this study, we examined whether rs2242446 and rs5569 genetic variants are related to the etiology of MDD using a meta-analysis. Relevant case-control studies were retrieved by database searching and selected according to established inclusion criteria.

RESULTS

Eight articles were identified that tested the relationship between the NET T-182C and/or G1287A polymorphism and MDD. Statistical analyses revealed no significant association between these polymorphisms and MDD (OR=1.23, 95% CI=0.77-1.97, P=0.38 for T-182C; OR=1.00, 95% CI=0.78-1.29, P=0.99 for G1287A).

LIMITATIONS

The results must be treated with caution because of the small sample sizes of several included studies.

CONCLUSIONS

Our findings suggest that the NET T-182C and G1287A polymorphisms are not susceptibility factors for MDD.

Contributions of maltreatment and serotonin transporter genotype to depression in childhood, adolescence, and early adulthood

BACKGROUND

Past findings on gene-by-environment (G×E) effects on depression have been mixed, leading to a debate of the plausibility of such mechanisms and methodological considerations that warrant attention. A developmental systems perspective postulates that complex, multi-level G×E effects are likely contributors to depression.

METHODS

Participants from families experiencing low-income status at birth were followed over 28 years. Maltreatment was recorded prospectively using multiple means and sources. Depression was measured repeatedly using well-validated interviews in middle childhood, through adolescence, and into adulthood.

RESULTS

Findings support a G×E effect where the less efficient form of the promoter region of the serotonin transporter gene (5-HTTLPR) contributes to a vulnerability to depressogenic aspects of maltreatment in childhood and adolescence. The presence of less efficient forms of the 5-HTTLPR polymorphism and maltreatment together raised risk for depression. This G×E effect was present generally and also among those who reported clinical levels of depression at only one point in time.

LIMITATIONS

This study used a low-income sample which limits generalizability to other populations. Sample size and rates of different forms of depression and depression at individual developmental stages supported general analyses, but limited the sorts of specific sub-analyses that were possible.

CONCLUSIONS

These findings support the plausibility of G×E effects on depression during childhood, adolescence, and early adulthood, key periods for the development of depression. Ongoing debates about the presence of G×E effects would be well served by additional work that was theoretically informed and employed prospective, longitudinal methodologies with well-validated measures of key constructs.

The built environment and depressive symptoms among urban youth: A spatial regression study

This study evaluated spatial relationships between features of the built environment and youth depressive symptoms. Data used in this study came from the 2008 Boston Youth Survey Geospatial Dataset, which includes Boston high school students with complete residential information (n=1170). Features of the built environment (such as access to walking destinations and community design features) were created for 400- and 800-m street network buffers of the youths' residences. We computed standard Ordinary Least Squares (OLS) regression and spatial simultaneous autoregressive models. We found significant positive spatial autocorrelation in all of the built environment features at both spatial scales (all p=0.001), depressive symptoms (p=0.034) as well as in the OLS regression residuals (all p<0.001), and, therefore, fit spatial regression models. Findings from the spatial regression models indicate that the built environment can have depressogenic effects, which can vary by spatial scale, gender and race/ethnicity (though sometimes in unexpected directions, i.e. associations opposite to our expectations). While our results overall suggest that the built environment minimally influences youth depressive symptoms, additional research is needed, including to understand our results in the unexpected direction.

Youth genetic vulnerability to maternal depressive symptoms: 5-HTTLPR as moderator of intergenerational transmission effects in a multiwave prospective study

BACKGROUND

Maternal depressive symptoms are a strong predictor of increases in depressive symptoms in offspring, yet knowledge of individual differences that may moderate the association between youth and maternal symptoms is still relatively scant. Youth genetic susceptibility to maternal depressive symptoms in particular is a nearly unexplored area of research.

METHODS

This study used a multiwave prospective design and lagged hierarchical linear modeling analyses to examine whether youth 5-HTTLPR genotype moderated the longitudinal association between mother and youth depressive symptoms in a community sample (N = 241 youth). Maternal and youth symptoms were assessed every 3 months over 1 year (five waves of data).

RESULTS

Youth 5-HTTLPR interacted with idiographic elevations in maternal depressive symptoms (elevations relative to mothers' average level of symptoms) to predict prospective increases in youth symptoms 3 months later. Youth with the SS genotype experienced greatest increases in depressive symptoms when exposed to elevations in maternal symptoms. Youth 5-HTTLPR did not interact with maternal nomothetic elevations in depressive symptoms (severity of symptoms compared to the sample as a whole).

CONCLUSION

These findings advance knowledge on genetic susceptibility for intergenerational transmission of depression between mothers and their children.

EpiHealth: a large population-based cohort study for investigation of gene-lifestyle interactions in the pathogenesis of common diseases

The most common diseases affecting middle-aged and elderly subjects in industrialized countries are multigenetic and lifestyle related. Several attempts have been made to study interactions between genes and lifestyle factors, but most such studies lack the power to examine interactions between several genes and several lifestyle components. The primary objective of the EpiHealth cohort study is to provide a resource to study interactions between several genotypes and lifestyle factors in a large cohort (the aim is 300,000 individuals) derived from the Swedish population in the age range of 45-75 years regarding development of common degenerative disorders, such as cardiovascular diseases, cancer, dementia, joint pain, obstructive lung disease, depression, and osteoporotic fractures. The study consists of three parts. First, a collection of data on lifestyle factors by self-assessment using an internet-based questionnaire. Second, a visit to a test center where blood samples are collected and physiological parameters recorded. Third, the sample is followed for occurrence of outcomes using nationwide medical registers. This overview presents the study design and some baseline characteristics from the first year of data collection in the EpiHealth study.

Serotonin transporter genotype by environment: Studies on alcohol use and misuse in non-human and human primates

Much evidence indicates that gene-by-environment interactions (GxE) play a role in alcohol misuse. It has been proposed that interactions between serotonin and stress confer vulnerability for alcohol misuse. The present review examined studies of the interaction between the serotonin transporter linked polymorphic region (5-HTTLPR) genotype and stressful life events and alcohol-related phenotypes, in rhesus monkeys and humans. Ten studies were found that had investigated the interaction of 5-HTTLPR and various measures of stress and alcohol use or misuse, two studies of rhesus monkeys, and eight of humans. The results are contradictory. Important differences were reported in study samples, experimental designs, measures used to assess environmental variables, definitions and measurements of alcohol-related phenotypes, and in the statistical analyses. These differences may explain the contradictory results. Guidelines for future studies are suggested. Results are discussed in light of findings from molecular, non-human animal, and clinical studies. The review highlights the need for future studies examining associations of interactions between the serotonin transporter gene and environmental factors and alcohol misuse, especially in samples followed over time.

5-HTTLPR and early childhood adversities moderate cognitive and emotional processing in adolescence

BACKGROUND

Polymorphisms in the promoter region of the serotonin transporter gene (5-HTTLPR) and exposure to early childhood adversities (CA) are independently associated with individual differences in cognitive and emotional processing. Whether these two factors interact to influence cognitive and emotional processing is not known.

METHODOLOGY AND PRINCIPAL FINDINGS

We used a sample of 238 adolescents from a community study characterised by the presence of the short allele of 5-HTTLPR (LL, LS, SS) and the presence or absence of exposure to CA before 6 years of age. We measured cognitive and emotional processing using a set of neuropsychological tasks selected predominantly from the CANTAB® battery. We found that adolescents homozygous for the short allele (SS) of 5-HTTLPR and exposed to CA were worse at classifying negative and neutral stimuli and made more errors in response to ambiguous negative feedback. In addition, cognitive and emotional processing deficits were associated with diagnoses of anxiety and/or depressions.

CONCLUSION AND SIGNIFICANCE

Cognitive and emotional processing deficits may act as a transdiagnostic intermediate marker for anxiety and depressive disorders in genetically susceptible individuals exposed to CA.

Interaction of dopamine transporter gene and observed parenting behaviors on attention-deficit/hyperactivity disorder: a structural equation modeling approach

Emerging evidence suggests that some individuals may be simultaneously more responsive to the effects from environmental adversity and enrichment (i.e., differential susceptibility). Given that parenting behavior and a variable number tandem repeat polymorphism in the 3'untranslated region of the dopamine transporter (DAT1) gene are each independently associated with attention-deficit/hyperactivity disorder (ADHD), our goal was to evaluate the potential interactive effects of child DAT1 genotype with positive and negative parenting behaviors on childhood ADHD. We recruited an ethnically diverse sample of 150 six- to nine-year-old boys and girls with and without ADHD. Children were genotyped for a common polymorphism of the DAT1 gene, and objective counts of observed parenting behavior (i.e., negativity and praise) were obtained from a valid parent-child interaction task. Structural equation modeling was used to examine the interactive effects of DAT1 and observed parenting with a latent ADHD factor. We detected a significant interaction between observed praise and child DAT1 (coded additively), which suggested that praise was associated with increased ADHD, but only among youth with the 9/10 genotype. In addition, a marginally significant interaction between DAT1 (coded additively and recessively) and observed negativity emerged for ADHD, such that negativity was positively associated with ADHD but only for youth with the 9/9 genotype. Although differential susceptibility theory was not fully supported, these preliminary results suggest that interactive exchanges between parenting behavior and child genotype potentially contribute to the development of ADHD. Clinical implications for interactions between parenting behavior and child genotype are discussed.

Wirksamkeit universeller und selektiver Prävention von Depression im Kindes- und Jugendalter

Fragestellung: Depressive Störungen beginnen häufig im Kindesalter, sodass bereits frühzeitig präventive Maßnahmen einsetzten sollten. Ziel der vorliegenden Arbeit ist es, auf der Basis bereits publizierter systematischer Reviews und Metaanalysen die Evidenz der selektiven, indizierten und universellen Prävention für das Kindes- und Jugendalter zusammenfassend darzustellen und Empfehlungen für die Praxis abzuleiten. Methodik: Zwischen 1990 und 2012 wurde in wissenschaftlichen Datenbanken nach deutsch und englischsprachigen Arbeiten zur Prävention von Depression im Kindes- und Jugendalter recherchiert. 10 systematische Reviews und Metaanalysen wurden eingeschlossen. Diese untersuchten insgesamt 121 ausschließlich kontrollierte Studien zu 52 universellen, 46 selektiven und 19 indizierten Präventionsprogrammen. Vier Studien kombinierten selektive und indizierte Prävention. Ergebnisse: Im Vergleich zu unbehandelten Kontrollgruppen gibt es sowohl für selektive und indizierte als auch universelle Prävention Evidenz für deren Wirksamkeit in der Reduktion depressiver Symptome. Dies gilt kurzfristig und bis zu einem Follow-up- Zeitraum von 9 Monaten. Selektive Ansätze zeigen Wirksamkeitsnachweise bis 12 Monate. Die Effektstärken sind meist niedrig. Wenn die Vergleiche mit Placebo- Kontrollgruppen durchgeführt werden, ist die Evidenz deutlich geringer oder nicht nachweisbar. Schlussfolgerungen: Die Ergebnisse der einzelnen Reviews sind sehr heterogen. Wichtig erscheint zukünftig zu klären, welche Faktoren für wirksame Prävention verantwortlich sind und wie die Präventionsprogramme erfolgreich in die Praxis integriert werden können.

Epigenetik–Revolution der Entwicklungspsychopathologie?

Die Epigenetik, die sich mit der Bedeutung der Gene im Kontext der menschlichen Entwicklung beschäftigt, konnte zeigen, dass genetische Wirkungen auf die Entwicklung immer auf einer Wechselwirkung zwischen Genom und Umwelt basieren. Die Annahme, der genetische Einfluss auf die (psychische) Entwicklung sei konstant und nur durch gentechnologische Maßnahmen veränderbar, ist demnach offenbar ein Fehlschluss. Es werden Grundbegriffe der Epigenetik und aktuelle Forschungsergebnisse erörtert. Desweiteren wird diskutiert, ob epigenetische Prozesse die Pathogenese psychischer Störungen beeinflussen und ob diese Prozesse an bestimmte Entwicklungsphasen gebunden sind. Anschließend wird die Epigenetik im Kontext der Klinischen Kinderpsychologie betrachtet. Es wird diskutiert, ob die Epigenetik die Entwicklungspsychopathologie grundlegend verändert und welche Konsequenzen die neuen epigenetischen Erkenntnisse für die Klinische Kinderpsychologie bereithalten.

Challenges and opportunities in genome-wide environmental interaction (GWEI) studies

The interest in performing gene-environment interaction studies has seen a significant increase with the increase of advanced molecular genetics techniques. Practically, it became possible to investigate the role of environmental factors in disease risk and hence to investigate their role as genetic effect modifiers. The understanding that genetics is important in the uptake and metabolism of toxic substances is an example of how genetic profiles can modify important environmental risk factors to disease. Several rationales exist to set up gene-environment interaction studies and the technical challenges related to these studies-when the number of environmental or genetic risk factors is relatively small-has been described before. In the post-genomic era, it is now possible to study thousands of genes and their interaction with the environment. This brings along a whole range of new challenges and opportunities. Despite a continuing effort in developing efficient methods and optimal bioinformatics infrastructures to deal with the available wealth of data, the challenge remains how to best present and analyze genome-wide environmental interaction (GWEI) studies involving multiple genetic and environmental factors. Since GWEIs are performed at the intersection of statistical genetics, bioinformatics and epidemiology, usually similar problems need to be dealt with as for genome-wide association gene-gene interaction studies. However, additional complexities need to be considered which are typical for large-scale epidemiological studies, but are also related to "joining" two heterogeneous types of data in explaining complex disease trait variation or for prediction purposes.

Anxiety sensitivity in adolescence and young adulthood: the role of stressful life events, 5HTTLPR and their interaction

BACKGROUND

Cognitive biases have long been hypothesized to influence the development and maintenance of symptoms of internalizing problems. Anxiety sensitivity represents one such bias and refers to sensitivity to the physical and emotional symptoms of anxiety and the belief that these are harmful. Twin studies indicate a role for both environmental and genetic influences on anxiety sensitivity. However, little work has been done specifying environments or genes involved in this phenotype. In light of this, we looked at the association between stressful life events, the serotonin transporter gene polymorphism (5HTTLPR), and anxiety sensitivity in a longitudinal sample of adolescents.

METHODS

Stressful life events and anxiety sensitivity were measured in over 1,500 individuals at three time points (mean ages 15, 17, and 20 years). 5HTTLPR was genotyped in 1,109 participants.

RESULTS

There was consistent evidence for an association between stressful life events and both anxiety sensitivity and change in anxiety sensitivity over time. Although the effect of independent stressful life events was relatively short lived, dependent stressful life events were associated with anxiety sensitivity over time. There was no evidence for a main effect of 5HTTLPR on anxiety sensitivity. 5HTTLPR genotype did not moderate the effect of stressful life events on anxiety sensitivity.

CONCLUSIONS

The current study extends previous work by showing that stressful life events, independent of the individual, explained change in cognitions associated with anxiety and depression. This effect does not, however, appear to be moderated by genotype.