The influence of five monoamine genes on trajectories of depressive symptoms across adolescence and young adulthood

Understanding stability and change in depressive symptom trajectories across young adulthood through the lens of career development: A mixed-methods study

Research has documented both stable and nonstable trajectories of depressive symptoms across young adulthood, but has not explored the mechanisms that might explain change in level of depressive affect over time. To explore this question, the current study draws on data from an Israeli longitudinal study of 205 young adults who reported their depressed symptoms four times from ages 23 to 35 years. Employing a latent profile analysis (LPA), three distinct trajectories of depressive symptoms were identified: stable low, moderate and decreasing, and stable high. To understand how stability and change in the course of depressive symptoms across time aligns with career development, 60 participants (20 from each profile), who had completed in-depth career development history interviews at age 29, were randomly selected. Subjecting the interviews to qualitative analysis showed that participants belonging to the stable low depressive symptoms trajectory were more likely to be intrinsically motivated, having the capacity to learn from their experiences, which resulted in a more successful career pursuit. In contrast, participants who consistently exhibited a high level of depressive affect were more likely to lack motivation, tended to feel at a loss, and were less likely to know what they want to do with their lives. Participants who were identified as belonging to the moderate and decreasing trajectory were more likely to describe the lack of a clear view of their future career plans. However, due to encouragement from significant others, they eventually found their niche. Conceptually, findings underscore the importance of understanding career factors that could covary with stability or change in the level of depressive symptoms during young adulthood.

The importance of a multidimensional approach to the preclinical study of major depressive disorder and apathy

Both the neuropsychiatric syndrome of apathy and major depressive disorder comprise a heterogenous cluster of symptoms which span multiple behavioural domains. Despite this heterogeneity, there is a tendency in the preclinical literature to conclude a MDD or apathy-like phenotype from a single dimensional behavioural task used in isolation, which may lead to inaccurate phenotypic interpretation. This is significant, as apathy and major depressive disorder are clinically distinct with different underlying mechanisms and treatment approaches. At the clinical level, apathy and major depressive disorder can be dissociated in the negative valence (loss) domain of the Research Domain Criteria. Symptoms of MDD in the negative valence (loss) domain can include an exaggerated response to emotionally salient stimuli and low mood, while in contrast apathy is characterised by an emotionally blunted state. In this article, we highlight how using a single dimensional approach can limit psychiatric model interpretation. We discuss how integrating behavioural findings from both the positive and negative (loss) valence domains of the Research Domain Criteria can benefit interpretation of findings. We focus particularly on behaviours relating to the negative valence (loss) domain, which may be used to distinguish between apathy and major depressive disorder at the preclinical level. Finally, we consider how future approaches using home cage monitoring may offer a new opportunity to detect distinct behavioural profiles and benefit the overall translatability of findings.

How Early Stressful Life Experiences Combine With Adolescents' Conjoint Health Risk Trajectories to Influence Cardiometabolic Disease Risk in Young Adulthood

Research has primarily focused on additive (unique) associations between early stressful life experiences (specifically, socioeconomic adversity and maltreatment) and young adults' cardiometabolic disease risk without considering multiplicative (synergistic) influences. Furthermore, research has not fully considered the varying patterns of health risk trajectories (e.g., substance use, obesogenic-related behaviors, depressive symptoms) across adolescence and the transition to young adulthood that may link earlier stressful experiences and later cardiometabolic disease risk. This study examined heterogeneity in conjoint health risk trajectories from adolescence to the transition to young adulthood and their additive and multiplicative (synergistic) influences with early stressful life experiences on cardiometabolic disease risk in young adulthood using data from the National Longitudinal Study of Adolescent to Adult Health (n = 9,421; 55.6% female) over a period of 13 years. Four distinct conjoint health risk trajectories were identified considering trajectories of substance use behaviors, obesogenic-related behaviors, and depressive symptoms: (a) overall high-risk, (b) behavioral risks, (c) psycho-obesogenic risks, and (d) overall low-risk. Socioeconomic adversity and maltreatment were additively and multiplicatively associated with cardiometabolic disease risk in young adulthood. Individuals with overall high-risk conjoint trajectories averaged higher cardiometabolic disease risk in young adulthood when they were exposed to early socioeconomic adversity. Implications for personalized interventions for individuals who have experienced multiple forms of health risks are discussed.

Association of DRD4 exon III and 5-HTTLPR VNTR genetic polymorphisms with psychiatric symptoms in hemodialysis patients

Mental illness is prevalent among hemodialysis (HD) patients. Given that the dopaminergic and serotonergic pathways are involved in the etiology of psychiatric disease, this study evaluated the genetic association of dopamine D4 receptor (DRD4) and serotonin transporter (SLC6A4) genes with psychiatric symptom susceptibility among HD patients. Hospital Anxiety and Depression Scale (HADS) was used to assess anxiety and depressive symptoms among patients (n = 265). Genetic polymorphisms of DRD4 (48 bp VNTR) and SLC6A4 (5-HTTLPR VNTR and rs25531) were examined using a conventional polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique, as appropriate. Significant differences were observed in the distribution of 5-HTTLPR genotypes, SLC6A4 tri-allelic-phased genotype, and DRD4-Exon III VNTR genotypes/alleles between patients with anxiety symptoms versus those with normal/borderline conditions (p<0.05). Binary logistic regression analyses showed that the heterozygous 4,5 VNTR genotype of DRD4 was associated with a higher risk of anxiety symptoms after adjusting for other covariates (odds ratio = 4.25, p = 0.028). None of the studied polymorphisms was linked to depression in HD patients. Collectively, the current findings provide genetic clues to psychopathology in HD patients and suggest that the DRD4 exon III VNTR polymorphism is involved in the etiology of anxiety in this patient population.

Epigenetic regulation of DAT gene promoter modulates the risk of externalizing and internalizing behaviors on a normative population: An explorative study

Accumulating research addressed epigenetic modifications and their role on behavioral phenotypes. We recently proposed to study methylation dynamics of two CpG motifs within the 5'-UTR of dopamine transporter (DAT) gene. Starting from a normative population sample of young adults, we selected three sub-groups based on their prevalent symptoms: subjects were assigned to Internalizing, Externalizing and Low-risk sub-groups according to elevated scores in specific phenotypic scales. Using a new approach, we calculated three independent matrixes of cross-correlation between CpG methylation levels, one within each phenotypic sub-group, to determine in which dynamics did the sub-groups differ. We found specific cross-correlation patterns in Externalizing (CpG1, 2 and 3, opposite to the methylation at CpG6) and Internalizing individuals (CpG1 methylation opposite to CpG2, 3 and 6), while Low-risk individuals could follow both trends. The aim of our study was to look for a specific DAT methylation pattern, providing a biomarker that allows early identification of the risk for psycho-pathological deviance.

Effects of Acute Tryptophan Depletion on Human Taste Perception

Taste perception has been reported to vary with changes in affective state. Distortions of taste perception, including blunted recognition thresholds, intensity, and hedonic ratings have been identified in those suffering from depressive disorders. Serotonin is a key neurotransmitter implicated in the etiology of anxiety and depression; systemic and peripheral manipulations of serotonin signaling have previously been shown to modulate taste detection. However, the specific effects of central serotonin function on taste processing have not been widely investigated. Here, in a double-blind placebo-controlled study, acute tryptophan depletion was used to investigate the effect of reduced central serotonin function on taste perception. Twenty-five female participants aged 18-28 attended the laboratory on two occasions at least 1 week apart. On one visit, they received a tryptophan depleting drink and on the other, a control drink was administered. Approximately, 6 h after drink consumption, they completed a taste perception task which measured detection thresholds and supra-threshold perceptions of the intensity and pleasantness of four basic tastes (sweet, sour, bitter, and salt). While acutely reducing central levels of serotonin had no effect on the detection thresholds of sweet, bitter, or sour tastes, it significantly enhanced detection of salt. For supra-threshold stimuli, acutely reduced serotonin levels significantly enhanced the perceived intensity of both bitter and sour tastes and blunted pleasantness ratings of bitter quinine. These findings show manipulation of central serotonin levels can modulate taste perception and are consistent with previous reports that depletion of central serotonin levels enhances neural and behavioral responsiveness to aversive signals.

A Person-Centered Perspective on the Role of Peer Support and Extreme Peer Orientation in Youth with Type 1 Diabetes: A Longitudinal Study

BACKGROUND

Despite clear evidence that peers are crucial for youth development, research on the role of peers for youth with Type 1 diabetes (T1D) is scarce.

PURPOSE

The present study identified trajectory classes of perceived peer functioning in youth with T1D, based on peer support and extreme peer orientation (EPO). Further, classes were compared with respect to their trajectories of depressive symptoms, diabetes-specific distress, treatment adherence, and HbA1c values.

METHODS

Five hundred and fifty-nine youth (14-25 years) with T1D completed questionnaires at baseline, 1, 2, and 3 years later. Latent class growth analysis identified classes of perceived peer functioning. Multigroup latent growth curve modelling assessed whether these classes were characterized by different trajectories of general and diabetes-specific functioning.

RESULTS

A socially normative class (48%) was characterized by trajectories of high support and low EPO over time. A socially reserved class (29%) was characterized by low support and EPO, and a socially oriented class (17%) by high support and EPO. Finally, a socially vulnerable class (6%) was characterized by low support and high EPO. The normative class functioned significantly better over time than the other classes. The vulnerable class functioned significantly worse compared to the reserved class, despite experiencing equally low levels of support.

CONCLUSIONS

The results underscore the need to take youths' orientation toward the peer context into account alongside support when tapping into the role of peers, because individuals with low levels of support and EPO functioned substantially better than individuals with similar low levels of support but high levels of EPO.

Loneliness, Social Anxiety Symptoms, and Depressive Symptoms in Adolescence: Longitudinal Distinctiveness and Correlated Change

Loneliness, social anxiety symptoms, and depressive symptoms are internalizing problems that are highly intertwined and often co-occur during adolescence. This overlap and co-occurrence raises the question whether three different labels are used for the same underlying phenomenon. The present study adopts a comprehensive approach to this issue by investigating the development of the three phenomena simultaneously. Specifically, this study aimed to investigate (1) the developmental trend for all three internalizing problems separately, (2) whether they are best described by a single developmental trend, (3) how they co-develop across adolescence, and (4) gender differences in this co-development. The analyses were run in three three-wave longitudinal samples of adolescents with one-year intervals in order to verify the robustness of the findings. Sample 1 (roughly ages 15, 16, and 17) comprised 549 adolescents (63% girls), and Samples 2 and 3 (roughly ages 13, 14, and 15) comprised 811 adolescents (46% girls) and 1101 adolescents (52% girls), respectively. Latent growth curve modeling for the three phenomena separately showed either small increases or stable patterns. A comparison of a Multiple Indicator Latent Growth Model (MILGM) with a Parallel Process Latent Growth Curve Modeling (PPLGCM) showed that the three internalizing problems followed unique, but related, developmental trends across adolescence. The intercepts of the three phenomena were positively correlated with one another in all samples and increases in loneliness were associated consistently with increases in social anxiety symptoms. Only in Sample 3 evidence was found for a similar association between loneliness and depressive symptoms and between social anxiety symptoms and depressive symptoms. Except for differences in initial levels, gender differences in the development of the three problems were limited. Overall, the results of the present study clearly indicate that the three internalizing problems are longitudinally distinct from one another, but co-develop across adolescence.

Associations Among Monoamine Neurotransmitter Pathways, Personality Traits, and Major Depressive Disorder

Major depressive disorder (MDD) is a complex psychiatric disease requiring multidisciplinary approaches to identify specific risk factors and establish more efficacious treatment strategies. Although the etiology and pathophysiology of MDD are not clear until these days, it is acknowledged that they are almost certainly multifactorial and comprehensive. Monoamine neurotransmitter system dysfunction and specific personality traits are independent risk factors for depression and suicide. These factors also demonstrate complex interactions that influence MDD pathogenesis and symptom expression. In this review, we assess these relationships with the aim of providing a reference for the development of precision medicine.

Early socioeconomic adversity and cardiometabolic risk in young adults: mediating roles of risky health lifestyle and depressive symptoms

The study examined the mediating roles of risky health lifestyle and depressive symptoms in relation to childhood/adolescence adversity and young adult cardiometabolic risk with data from the National Longitudinal Study of Adolescent to Adult Health (n = 9421). Four classes of youth emerged from a latent class analysis with varying early adversity patterns: (a) both low disadvantaged SES and stressful experience (54.8%), (b) high disadvantaged SES and low stressful experience (31.0%), (c) low disadvantaged SES and high stressful experience (10.9%), and (d) both high disadvantaged SES and stressful experience (3.3%). Early adversity had multiple direct and indirect effects on CM risk for those experiencing SES-related adversities. Instead, early adversity generated mediational processes between adversity and CM risks through risky health lifestyle and depressive symptoms for those experiencing stressful experience. Implications for intervention when dealing with youths who have experienced multiple forms of early adversity are discussed.

Sex differences modulating serotonergic polymorphisms implicated in the mechanistic pathways of risk for depression and related disorders

Despite consistent observations of sex differences in depression and related emotional disorders, we do not yet know how these sex differences modulate the effects of genetic polymorphisms implicated in risk for these disorders. This Mini-Review focuses on genetic polymorphisms of the serotonergic system to illustrate how sex differences might modulate the neurobiological pathways involved in the development of depression. We consider the interacting role of environmental factors such as early-life stress. Given limited current knowledge about this topic, we highlight methodological considerations, challenges, and guidelines for future research. © 2016 Wiley Periodicals, Inc.

Genetic moderation of multiple pathways linking early cumulative socioeconomic adversity and young adults' cardiometabolic disease risk

Recent research suggests that psychosocial resources and life stressors are mediating pathways explaining socioeconomic variation in young adults' health risks. However, less research has examined both these pathways simultaneously and their genetic moderation. A nationally representative sample of 11,030 respondents with prospective data collected over 13 years from the National Study of Adolescent to Adult Health was examined. First, the association between early cumulative socioeconomic adversity and young adults' (ages 25-34) cardiometabolic disease risk, as measured by 10 biomarkers, through psychosocial resources (educational attainment) and life stressors (accelerated transition to adulthood) was examined. Second, moderation of these pathways by the serotonin transporter linked polymorphic region gene (5-HTTLPR) was examined. There was evidence for the association between early socioeconomic adversity and young adults' cardiometabolic disease risk directly and indirectly through educational attainment and accelerated transitions. These direct and mediating pathways were amplified by the 5-HTTLPR polymorphism. These findings elucidate how early adversity can have an enduring influence on young adults' cardiometabolic disease risk directly and indirectly through psychosocial resources and life stressors and their genetic moderation. This information suggests that effective intervention and prevention programs should focus on early adversity, youth educational attainment, and their transition to young adulthood.

Depressive symptom trajectories in late adolescence and early adulthood: A systematic review

OBJECTIVE

In adolescents and young adults, depressive symptoms are highly prevalent and dynamic. For clinicians, it is difficult to determine whether a young person reporting depressive symptoms is at risk of developing ongoing mood difficulties or whether symptoms form part of a transient maturational process. Trajectory analyses of longitudinally assessed symptoms in large cohorts have the potential to untangle clinical heterogeneity by determining subgroups or classes of symptom course and their risk factors, by interrogating the impact of known or suspected risk factors on trajectory slope and intercept and by tracing the interrelation between depressive symptoms and other clinical outcomes over time.

METHOD

We conducted a systematic review of trajectory studies conducted in cohorts including people aged between 15 and 25 years.

RESULTS

We retrieved 47 relevant articles. These studies suggest that young people fall into common mood trajectory classes and that class membership and symptom course are mediated by biological and environmental risk factors. Furthermore, studies provide evidence that high and persistent depressive symptoms are associated with a range of concurrent health and behavioral outcomes.

CONCLUSION

Findings could assist in the formulation of novel concepts of depressive disorders in young people and inform preventive strategies and predictive models for clinical practice.

Stress Processes Linking Parent-Child Disconnection to Disease Risk in Young Adulthood: Amplification by Genotype

Previous studies have documented that early stressful family relationships influence subsequent stressful life circumstances and health outcomes over the life course. Less is known, however, about whether stressful parent-child relationships increase the influence of proximal stressors on youth health operating as a stress-sensitizing life context, and individual genetic variations have effects on these developmental processes. Informed by life course stress process theory, which focuses on the proliferation, accumulation, and interactions of stressors over the life course as health risks, we examined whether (a) parent-child disconnection influences the occurrence of stressful life events in young adulthood, (b) parent-child disconnection potentiates the impact of stressful life events on young adults' health, or (c) potential health impact is intensified further by individual genotype. Using longitudinal data from a nationally representative sample of 11,290 adolescents (Mean age 15.5 years, 53% female) over a period of 13 years, we found parent-child disconnection influenced young adults' stressful life events and amplified the impact of stressful life events on cardio-metabolic disease risk. We also found the association between stressful life events and cardio-metabolic disease risk was further intensified by the 5-HTTLPR polymorphism. Our findings demonstrate that stressful family relationships not only initiate stress processes over the early life course, but also sensitize youth to stressors, and that 5-HTTLPR polymorphism interacts with stressful life experiences to predict heightened disease risk.

Pubertal Stress and Nutrition and their Association with Sexual Orientation and Height in the Add Health Data

A number of studies have indicated that gay men tend to be shorter, on average, than heterosexual men. Less evidence exists that lesbian women are taller, on average, than heterosexual women. The most popular explanation of the association between sexual orientation and height involves prenatal factors, such that, for example, gay men may have been exposed to lower than typical androgens during fetal development, which impacts their height and sexual orientation as adults. An alternative explanation involves stress, given that stress has been associated with sexual minority identification and with lower height. Another alternative explanation involves nutrition, although its relationship is less clear with sexual minority identification. Using the Add Health data, which is a large, nationally representative and longitudinal sample of American adolescents (n = 14,786), we tested a mediation model, such that sexual orientation → pubertal stress/nutrition → height. Within men, we found that gay men (n = 126) were shorter, on average, than heterosexual men (n = 6412). None of the 24 pubertal stress-related and 15 pubertal nutrition-related variables assessed in the Add Health data mediated the relationship between sexual orientation and height in men. Within women, lesbians (n = 75) did not differ significantly in stature compared to heterosexual women (n = 6267). Thus, prenatal mechanisms (e.g., hormones, maternal immune response) are likely better candidates for explaining the height difference between gay men and heterosexual men.

Genome-Wide Meta-Analysis of Longitudinal Alcohol Consumption Across Youth and Early Adulthood

The public health burden of alcohol is unevenly distributed across the life course, with levels of use, abuse, and dependence increasing across adolescence and peaking in early adulthood. Here, we leverage this temporal patterning to search for common genetic variants predicting developmental trajectories of alcohol consumption. Comparable psychiatric evaluations measuring alcohol consumption were collected in three longitudinal community samples (N=2,126, obs=12,166). Consumption-repeated measurements spanning adolescence and early adulthood were analyzed using linear mixed models, estimating individual consumption trajectories, which were then tested for association with Illumina 660W-Quad genotype data (866,099 SNPs after imputation and QC). Association results were combined across samples using standard meta-analysis methods. Four meta-analysis associations satisfied our pre-determined genome-wide significance criterion (FDR<0.1) and six others met our 'suggestive' criterion (FDR<0.2). Genome-wide significant associations were highly biological plausible, including associations within GABA transporter 1, SLC6A1 (solute carrier family 6, member 1), and exonic hits in LOC100129340 (mitofusin-1-like). Pathway analyses elaborated single marker results, indicating significant enriched associations to intuitive biological mechanisms, including neurotransmission, xenobiotic pharmacodynamics, and nuclear hormone receptors (NHR). These findings underscore the value of combining longitudinal behavioral data and genome-wide genotype information in order to study developmental patterns and improve statistical power in genomic studies.

Are infants differentially sensitive to parenting? Early maternal care, DRD4 genotype and externalizing behavior during adolescence

Insensitive and unresponsive caregiving during infancy has been linked to externalizing behavior problems during childhood and adolescence. The 7-repeat (7r) allele of the dopamine D4 receptor (DRD4) gene has meta-analytically been associated with a heightened susceptibility to adverse as well as supportive environments. In the present study, we examined long-term effects of early maternal care, DRD4 genotype and the interaction thereof on externalizing and internalizing psychopathology during adolescence. As part of an ongoing epidemiological cohort study, early maternal care was assessed at child's age 3 months during a nursing and playing situation. In a sample of 296 offspring, externalizing and internalizing symptoms were assessed using a psychiatric interview conducted at age 15 years. Parents additionally filled out a questionnaire on their children's psychopathic behaviors. Results indicated that adolescents with the DRD4 7r allele who experienced less responsive and stimulating early maternal care exhibited more symptoms of ADHD and CD/ODD as well as higher levels of psychopathic behavior. In accordance with the hypothesis of differential susceptibility, 7r allele carriers showed fewer ADHD symptoms and lower levels of psychopathic behavior when exposed to especially beneficial early caregiving. In contrast, individuals without the DRD4 7r allele proved to be insensitive to the effects of early maternal care. This study replicates earlier findings with regard to an interaction between DRD4 genotype and early caregiving on externalizing behavior problems in preschoolers. It is the first one to imply continuity of this effect until adolescence.

Relationship between depressive mood and eating disorders in a non-clinical young female sample: a one-year longitudinal analysis of cross-lagged and simultaneous effects

Although it is generally agreed that eating disorders (EDs) and depressive mood (DM) are related, the main ambiguity arises from difficulties in determining their cause-effect relationships. The aim of this study was to examine the longitudinal reciprocal causation between EDs and DM among female students. Several models (cross-lagged effects and simultaneous effects) were tested in order to disentangle the prospective relationships between DM (measured by the Beck Depression Inventory-Short Form) and EDs (measured by the Eating Attitudes Test-26) using structural equation modeling with latent variables on one-year longitudinal data. A total of 567 female students were interviewed at the beginning of the first university year (T1); 373 of them were re-interviewed 6 months later (T2), and 359 were re-interviewed after a further 6 months (T3). The results support (1) the prospective reciprocal effects model and (2) the simultaneous reciprocal effects model. The implications of the findings in terms of theoretical improvements and effective treatments are discussed.

A longitudinal analysis of the effects of a DRD4 polymorphism on marijuana use

The current study used a variable- and person-centered approach to examine whether a DRD4 polymorphism explained within-individual differences in frequency of marijuana use from adolescence into emerging adulthood. Data were analyzed from 1897 respondents from the genetic subsample of the National Longitudinal Study of Adolescent Health (Add Health) at waves I (ages 13-17), II (ages 14-18), and III (ages 21-25). Latent class growth model results revealed that marijuana use was characterized by four trajectories (non-users/experimenters, increasers, desisters, and chronic users), and that the DRD4 polymorphism differentiated increasers from non-users/experimenters. Overall, the results suggested that the DRD4 polymorphism may be relevant to differences in the developmental trajectories of marijuana use.

Dopamine receptor (D4) polymorphism is related to comorbidity between marijuana abuse and depression

The rates of marijuana abuse are steadily increasing in the U.S. Data suggest that comorbid marijuana abuse and depression is associated with worse outcomes than either diagnosis. Genetic studies independently link the DRD4 gene polymorphism to substance use and to internalizing disorders, but no study has examined whether the DRD4 polymorphism is linked to comorbid marijuana use and depression in a population sample. This study examined associations between the DRD4 gene 48bp VNTR polymorphism and comorbidity between marijuana use frequency and depression in a diverse, non-clinical adolescent sample (n=1882; ages 14 to 18) from the National Longitudinal Study of Adolescent Health (Add Health). Multinomial regression analyses indicated that the odds of being comorbid for depressive symptoms and marijuana use are approximately 2.5≥ with the ≥7R/≥7R genotype than youths who carry the <7R/<7R genotype, controlling for the effects of ethnicity, gender, age, violent victimization, and alcohol related problems. Findings provide genetic clues for psychopathology characterized by prominent externalizing and internalizing features.

Genes, environments, and developmental research: methods for a multi-site study of early substance abuse

The importance of including developmental and environmental measures in genetic studies of human pathology is widely acknowledged, but few empirical studies have been published. Barriers include the need for longitudinal studies that cover relevant developmental stages and for samples large enough to deal with the challenge of testing gene-environment-development interaction. A solution to some of these problems is to bring together existing data sets that have the necessary characteristics. As part of the National Institute on Drug Abuse-funded Gene-Environment-Development Initiative, our goal is to identify exactly which genes, which environments, and which developmental transitions together predict the development of drug use and misuse. Four data sets were used of which common characteristics include (1) general population samples, including males and females; (2) repeated measures across adolescence and young adulthood; (3) assessment of nicotine, alcohol, and cannabis use and addiction; (4) measures of family and environmental risk; and (5) consent for genotyping DNA from blood or saliva. After quality controls, 2,962 individuals provided over 15,000 total observations. In the first gene-environment analyses, of alcohol misuse and stressful life events, some significant gene-environment and gene-development effects were identified. We conclude that in some circumstances, already collected data sets can be combined for gene-environment and gene-development analyses. This greatly reduces the cost and time needed for this type of research. However, care must be taken to ensure careful matching across studies and variables.

Resilience and measured gene–environment interactions

The past decade has witnessed an exponential growth in studies that have attempted to identify the genetic polymporphisms that moderate the influence of environmental risks on mental disorders. What tends to be neglected in these Gene × Environment (G × E) interaction studies has been a focus on resilience, which refers to a dynamic pattern of positive adaptation despite the experience of a significant trauma or adversity. In this article, we argue that one step toward advancing the field of developmental psychopathology would be for G × E research to consider resilience instead of focusing almost exclusively on mental disorders. After providing an up-to-date summary on the expanding definitions and models of resilience, and the available evidence regarding measured G × E studies of childhood maltreatment, we discuss why resilience would be a worthwhile phenotype for studies of measured G × E. First, although G × E hypotheses require that there be an environmental risk (e-risk) involved in a causal process that leads to psychopathology, e-risks are typically not included in the diagnostic criteria for most psychiatric disorders. In contrast, resilience by definition includes an e-risk. Second, G × E hypotheses require that there is evidence of variability in response to an environmental stressor, and resilience often represents the positive end on this continuum of adaptation. Third, both resilience and G × E are best understood from a developmental perspective. Fourth, although resilient outcomes are not public health concerns, the types of adversities (e.g., childhood maltreatment, poverty, or exposure to natural disasters) that are often investigated in studies of resilience certainly are. Understanding how some individuals, perhaps because of their genetic makeup, are able to withstand such adversities can inform prevention and intervention efforts to improve mental health.