Depressive symptoms in children and adolescents: etiological links between normality and abnormality: a research note

Association of etiological factors across the extreme end and continuous variation in disordered eating in female Swedish twins

BACKGROUND

Accumulating evidence suggests that many psychiatric disorders etiologically represent the extreme end of dimensionally distributed features rather than distinct entities. The extent to which this applies to eating disorders (EDs) is unknown.

METHODS

We investigated if there is similar etiology in (a) the continuous distribution of the Eating Disorder Inventory-2 (EDI-2), (b) the extremes of EDI-2 score, and (c) registered ED diagnoses, in 1481 female twin pairs at age 18 years (born 1992-1999). EDI-2 scores were self-reported at age 18. ED diagnoses were identified through the Swedish National Patient Register, parent-reported treatment and/or self-reported purging behavior of a frequency and duration consistent with DSM-IV criteria. We differentiated between anorexia nervosa (AN) and other EDs.

RESULTS

The heritability of the EDI-2 score was 0.65 (95% CI 0.61-0.68). The group heritabilities in DeFries-Fulker extremes analyses were consistent over different percentile-based extreme groups [0.59 (95% CI 0.37-0.81) to 0.65 (95% CI 0.55-0.75)]. Similarly, the heritabilities in liability threshold models were consistent over different levels of severity. In joint categorical-continuous models, the twin-based genetic correlation was 0.52 (95% CI 0.39-0.65) between EDI-2 score and diagnoses of other EDs, and 0.26 (95% CI 0.08-0.42) between EDI-2 score and diagnoses of AN. The non-shared environmental correlations were 0.52 (95% CI 0.32-0.70) and 0.60 (95% CI 0.38-0.79), respectively.

CONCLUSIONS

Our findings suggest that some EDs can partly be conceptualized as the extreme manifestation of continuously distributed ED features. AN, however, might be more distinctly genetically demarcated from ED features in the general population than other EDs.

Parenting and prenatal risk as moderators of genetic influences on conduct problems during middle childhood

This study examines interactions of heritable influences, prenatal substance use, and postnatal parental warmth and hostility on the development of conduct problems in middle childhood for boys and girls. Participants are 561 linked families, collected in 2 cohorts, including birth parents, adoptive parents, and adopted children. Heritable influences on internalizing and externalizing (including substance use) problems were derived from birth mothers' and fathers' symptoms, diagnoses, and age of onset from diagnostic interviews, and the proportion of first-degree relatives with the same type of problems. Smoking during pregnancy (SDP) and alcohol use during pregnancy were assessed retrospectively from birth mothers at 5 months postpartum. Earlier externalizing problems and parental warmth and hostility and were assessed at 1 assessment prior to the outcome (Cohort II: 4.5 years; Cohort I: 7 years). Conduct problems were symptoms from a diagnostic interview assessed at age 6 (Cohort II) or 8 (Cohort I). Findings from regression analyses suggest that (a) SDP plays an important role for the development of conduct problems, (b) some relatively well-accepted effects (e.g., parental hostility) were less important when simultaneously considering multiple factors influencing the development of conduct problems, and (c) main effects of genetic risk and SDP, and interactions among genetic risk and postnatal warmth, SDP and postnatal warmth, and genetic risk, SDP, and postnatal hostility for conduct problems were important for boys' but not girls' conduct problems. Replication is needed, but the current results provide preliminary but empirically grounded hypotheses for future research testing complex developmental models of conduct problems. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Assessing the evidence for shared genetic risks across psychiatric disorders and traits

Genetic influences play a significant role in risk for psychiatric disorders, prompting numerous endeavors to further understand their underlying genetic architecture. In this paper, we summarize and review evidence from traditional twin studies and more recent genome-wide molecular genetic analyses regarding two important issues that have proven particularly informative for psychiatric genetic research. First, emerging results are beginning to suggest that genetic risk factors for some (but not all) clinically diagnosed psychiatric disorders or extreme manifestations of psychiatric traits in the population share genetic risks with quantitative variation in milder traits of the same disorder throughout the general population. Second, there is now evidence for substantial sharing of genetic risks across different psychiatric disorders. This extends to the level of characteristic traits throughout the population, with which some clinical disorders also share genetic risks. In this review, we summarize and evaluate the evidence for these two issues, for a range of psychiatric disorders. We then critically appraise putative interpretations regarding the potential meaning of genetic correlation across psychiatric phenotypes. We highlight several new methods and studies which are already using these insights into the genetic architecture of psychiatric disorders to gain additional understanding regarding the underlying biology of these disorders. We conclude by outlining opportunities for future research in this area.

Anxiety, Depression and Self-Esteem in Secondary School Children

With the introduction of a new curriculum and increased targets for schools, children are facing increased pressure to succeed in examinations at increasingly earlier ages. It is therefore necessary to emphasize the need for greater awareness of the distress that may be experienced by young children and adolescents as a result and implement provision for early interventions. The aim of this study was to investigate changes occurring in anxiety, affect, depression and self-esteem in secondary school children as they approached important school examinations and to examine variations between schools of differing design and status. There were a total of 520 participants, from four different schools in two school years (year 9, age 13-14 and year 11, age 15-16). Participants completed self-report questionnaires at two time points—firstly during regular term time and the second in the week immediately prior to the examinations. Gender differences were found in the majority of measures with females displaying greater levels of anxiety and negative affect immediately before the examinations, whereas males reported higher positive affect and self-esteem and lower depression and anxiety, even within the week prior to the examinations. Differences between the schools were also found. However, there were no significant differences between the two school years and the two times of testing. A number of trends were identified in relation to both gender differences and the influence of the type of school attended. Females, particularly those attending independent or grammar schools, reported a greater negative mood overall and before the examinations. It is suggested that there is a need for a school-based provision aimed at pro-actively increasing pupils self-esteem and to develop skills for dealing with stressful situations—particularly important examinations.

Combined Influences of Genes, Prenatal Environment, Cortisol, and Parenting on the Development of Children's Internalizing Versus Externalizing Problems

Research suggests that genetic, prenatal, endocrine, and parenting influences across development individually contribute to internalizing and externalizing problems in children. The present study tests the combined contributions of genetic risk for psychopathology, prenatal environments (maternal drug use and internalizing symptoms), child cortisol at age 4.5 years, and overreactive parenting influences across childhood on 6-year-old children's internalizing and externalizing problems. We used data from an adoption design that included 361 domestically adopted children and their biological and adopted parents prospectively followed from birth. Only parenting influences contributed (independently) to externalizing problems. However, genetic influences were indirectly associated with internalizing problems (through increased prenatal risk and subsequent morning cortisol), and parenting factors were both directly and indirectly associated with internalizing problems (through morning cortisol). Results suggest that prenatal maternal drug use/symptoms and children's morning cortisol levels are mechanisms of genetic and environmental influences on internalizing problems, but not externalizing problems, in childhood.

Genetic and environmental influences on depressive symptoms in Chinese adolescents

Adolescent depression is common and has become a major public health concern in China, yet little research has examined the etiology of depression in Chinese adolescents. In the present study, genetic and environmental influences on Chinese adolescent depressive symptoms were investigated in 1,181 twin pairs residing in Beijing, China (ages 11-19 years). Child- and parent-versions of the children's depression inventory were used to measure adolescents' depressive symptoms. For self-reports, genetic factors, shared environmental factors, and non-shared environmental factors accounted for 50, 5, and 45 % of the variation in depressive symptoms, respectively; for parent-reports, genetic factors, shared environmental factors, and non-shared environmental factors accounted for 51, 18, and 31 % of the variation, respectively. These estimates are generally consistent with previous findings in Western adolescents, supporting the cross-cultural generalizability of etiological model of adolescent depression. Neither qualitative nor quantitative sex differences were found in the etiological model. Future studies are needed to investigate how genes and environments work together (gene-environment interaction, gene-environment correlation) to influence depression in Chinese adolescents.

Genetic and environmental influences upon the CBCL/6-18 DSM-oriented scales: similarities and differences across three different computational approaches and two age ranges

Inasmuch as the newly established DSM-oriented CBCL/6-18 scales are to be increasingly employed to assess clinical/high-risk populations, it becomes important to explore their aetiology both within the normal- and the extreme range of variation in general population samples and to compare the results obtained in different age groups. We investigated by the Quantitative Maximum Likelihood, the De Fries-Fulker, and the Ordinal Maximum Likelihood methods the genetic and environmental influences upon the five DSM-oriented CBCL/6-18 scales in 796 twins aged 8-17 years belonging to the general population-based Italian Twin Registry. When children were analysed together regardless of age, most best-fitting solutions yielded genetic and non-shared environmental factors as the sole influences for DSM-oriented CBCL/6-18 behaviours, both for the normal and the extreme variations. When analyses were conducted separately for two age groups, shared environmental influences emerged consistently for Affective and Anxiety Problems in children aged 8-11. Oppositional-Defiant, Attention Deficit/Hyperactivity, and Conduct Problems appeared-with few exceptions-influenced only by genetic and non-shared environmental factors in both age groups, according to all three computational approaches. The De Fries-Fulker method appeared to be more sensitive in detecting shared environmental effects. Analysing the same set of data with different analytic approaches leads to better-balanced views on the aetiology of psychopathological behaviours in the developmental years.

The genetics of mood disorders

Studying the genetics of mood disorders has never been more exciting. We have moved rapidly from establishing the genetic basis of depression to asking questions about how genes are expressed. This has been made possible by the capacity to collect and sequence DNA for large samples cheaply. But "multidisciplinary" approaches investigating interrelationships between risk factors have also been increasingly adopted, encouraging collaborations between those studying genes and those studying the brain, cognition, and/or the social environment. In this review, we first describe findings from quantitative and molecular studies investigating the genetic basis of depression. Second, we present overviews of three hot topics of genetic research: gene-environment interplay, which considers how genetic factors shape exposure and responses toward the social environment; endophenotypic research, which identifies neurophysiological and psychological mediators of genetic risk; and epigenetics, which explain how early environments can foster changes in gene expression, altering subsequent emotional development.

Neuroticism, life events and negative thoughts in the development of depression in adolescent girls

Theories of depression suggest that cognitive and environmental factors may explain the relationship between personality and depression. This study tested such a model in early adolescence, incorporating neuroticism, stress-generation and negative automatic thoughts in the development of depressive symptoms. Participants (896 girls, mean age 12.3 years) completed measures of personality and depressive symptoms, and 12 months later completed measures of depressive symptoms, recent stressors and negative automatic thoughts. Path analysis supported a model in which neuroticism serves as a distal vulnerability for depression, conferring a risk of experiencing dependent negative events and negative automatic thoughts, which fully mediate the effect of neuroticism on later depression. A second path supported a maintenance model for depression in adolescence, with initial levels of depression predicting dependent negative events, negative automatic thoughts and subsequent depressive symptoms. Unexpectedly, initial depression was also associated with later independent life events. This study establishes potential mechanisms through which personality contributes to the development of depression in adolescent girls.

Phenotypic and genetic differentiation of anxiety-related behaviors in middle childhood

BACKGROUND

Anxiety-related behaviors (ARBs) are commonly observed during typical development, yet few studies have investigated their etiology in middle childhood. This study aimed to examine both the phenotypic and genetic differentiation of ARB subtypes within the general population at age 7 and 9. It constituted a follow-up to an earlier study of ARBs in preschool children.

METHODS

We investigated the phenotypic structure of ARBs in a large population-based twin sample, comprising 7,834 twin pairs at age 7 and 3,644 twin pairs at age 9. Quantitative genetic modeling techniques were then used to determine the relative influences of genetic and environmental factors upon different types of ARB and upon the covariation between them.

RESULTS

Factor analysis supported the presence of five ARB factors at both ages: negative cognitions, negative affect, fear, obsessive-compulsive behaviors, and social anxiety. Multivariate genetic analyses revealed significant genetic effects and a small but significant influence of shared environment for all ARB subtypes. There was a moderate level of genetic specificity for each subtype as well as some shared genetic effects. Shared environmental influences correlated highly across all types of ARB, whereas nonshared environmental effects were largely subtype specific.

CONCLUSIONS

The current results suggest that ARBs can be differentiated both phenotypically and genetically within middle childhood, with subtypes reflecting symptom groupings of diagnosable disorders but also aspects of temperament. Although some etiological risk factors lead to a generalized vulnerability to anxiety, others may serve to differentiate between different types of ARBs.

Estimating genetic and environmental influences on depressive symptoms in adolescence: differing effects on higher and lower levels of symptoms

We estimate the relative effect sizes of genetic and environmental influences on both higher and lower levels of depressive symptoms with attention to persistence over a 1-year period in the genetically informative subsample of adolescents participating in the National Longitudinal Study of Adolescent Health (Add Health). Shared environmental effects were significant for persistent higher levels of depressive symptoms but not nonpersistent symptoms. Genetic effects were significant for both persistent and nonpersistent lower levels of depressive symptoms. Nongenetic factors that promote similarity between siblings for high levels of depressive symptoms are important and should be considered in both etiological and applied research. Genetic contributions to lack of susceptibility to depression should be considered in biological models of depression suppression.

The effect of birth-weight with genetic susceptibility on depressive symptoms in childhood and adolescence

Low birth-weight has been associated with depression and related outcomes in adults, and with problem behaviours in children. This study aimed to examine the association between low birth-weight for gestation and depressive symptoms in children and adolescents and to examine whether the relationship is moderated by genetic risk for depression. An epidemiological, genetically sensitive design was used including 2,046 twins aged 8-17 years (1,023 families). Data were obtained by parental report and analysed using regression analysis. A small but significant association between birth-weight for gestation and early depressive symptoms was observed. The unit increase in depressive symptoms per unit decrease in birth-weight for gestation was greater for individuals at genetic or familial risk for depression. For low birth-weight children, genetic risk for depression moderated the influence of birth-weight for gestation in predicting early depressive symptoms. Birth-weight for gestation is moderated by genetic and familial risk for depression in influencing early depression symptoms. These observations have clinical implications in that the impact of being small for gestational age on depressive symptoms is greater in children at familial/genetic risk although the association between birth weight and depression does not imply causality.

Family conflict interacts with genetic liability in predicting childhood and adolescent depression

OBJECTIVE

To test for gene-environment interaction with depressive symptoms and family conflict. Specifically, to first examine whether the influence of family conflict in predicting depressive symptoms is increased in individuals at genetic risk of depression. Second, to test whether the genetic component of variance in depressive symptoms increases as levels of family conflict increase.

METHOD

A longitudinal twin design was used. Children ages 5 to 16 were reassessed approximately 3 years later to test whether the influence of family conflict in predicting depressive symptoms varied according to genetic liability. The conflict subscale of the Family Environment Scale was used to assess family conflict and the Mood and Feelings Questionnaire was used to assess depressive symptoms. The response rate to the questionnaire at time 1 was 73% and 65% at time 2. Controlling for initial symptoms levels (i.e., internalizing at time 1), primary analyses were conducted using ordinary least-squares multiple regression. Structural equation models, using raw score maximum likelihood estimation, were also fit to the data for the purpose of model fit comparison.

RESULTS

Results suggested significant gene-environment interaction specifically with depressive symptoms and family conflict. Genetic factors were of greater importance in the etiology of depressive symptoms where levels of family conflict were high. The effects of family conflict on depressive symptoms were greater in children and adolescents at genetic risk of depression.

CONCLUSIONS

The present results suggest that children with a family history of depression may be at an increased risk of developing depressive symptoms in response to family conflict. Intervention programs that incorporate one or more family systems may be of benefit in alleviating the adverse effect of negative family factors on children.

The Link between depression in mothers and offspring: an extended twin analysis

Family studies have shown that maternal depression is a risk factor for depression in children. It is unclear, however, to what extent the familial transmission of depression from mother to child involves genes and how much is due to environmental adversity. This study used an extended twin design to assess the importance of environmental factors in the association of depression in mothers and children while simultaneously accounting for genetic relatedness in a UK. community sample of twins aged 8 to 17 years and their mothers. A model that constrained the genetic and environmental parameters to be equal within the two generations and included genetic and environmental paths between mother and offspring (twins) was tested with data from 1468 families. Significant environmental paths were found when maternal ratings were used. When cross-informant data were used (maternal depression and child self-reports of depression), the environmental path was no longer significant. However, for cross-informant data where children were classified as having high depression scores or scores within the normal range, significant environmental effects were found. These findings are interpreted in light of the strengths and weaknesses of the extended twin and other designs.

Gene-environment interaction analysis of serotonin system markers with adolescent depression

We report analyses from a study of gene-environment interaction in adolescent depression. The sample was selected from 1990 adolescents aged 10-20 years: those with depression symptoms in the top or bottom 15% were identified and divided into high or low environmental risk groups. DNA was obtained from 377 adolescents, representing the four quadrants of high or low depression and high or low environmental risk. Markers within, or close to, each of the serotonergic genes 5HTT, HTR2A, HTR2C, MAOA (monoamine oxidase type A) and tryptophan hydroxylase (TPH) were genotyped. Environmental risk group was a nonsignificant predictor and sex was a significant predictor of the depression group. HTR2A and TPH significantly predicted the depression group, independent of the effects of sex, environmental risk group and their interaction. In addition, there was a trend for an effect of 5HTTLPR, which was significant in female subjects. Furthermore, there was a significant genotype-environmental risk interaction for 5HTTLPR in female subjects only, with the effect being in the same direction as another recent study, reaffirming that an important source of genetic heterogeneity is exposure to environmental risk.

Parental familial vulnerability, family environment, and their interactions as predictors of depressive symptoms in adolescents

OBJECTIVE

Familial risk for depression results from both biological and social influences. These may also be associated with other characteristics, including alcohol use, smoking, and body mass index (BMI), and with environmental risks such as social problems, life events, and educational level, all of which may be associated with depression in offspring. The authors examined the links between (1) parental familial vulnerability to depression and (2) the role of associated parental characteristics on severe adolescent depressive symptoms. Third, the authors explored the influence of family environment variables. Fourth, the authors sought interactions between parental familial vulnerability and family environment.

METHOD

Questionnaires were obtained from 1,294 parents of 1,818 adolescent offspring.

RESULTS

The odds of severe adolescent depressive symptoms increased by a factor of 1.5 per standard deviation increase in parental familial vulnerability to depression (odds ratio [OR] = 1.50). Parental BMI (OR = 1.05) and educational level (OR = 2.60) had significant influences independent of parental vulnerability. Analyses indicated a significant interaction such that those with high parental familial vulnerability, whose parents also had no qualifications, had a threefold risk of severe depressive symptoms.

CONCLUSIONS

Adolescents with a family history of depression whose parents also lack qualifications may be a target for intervention.

Assessing the effects of age, sex and shared environment on the genetic aetiology of depression in childhood and adolescence

BACKGROUND

Depressive symptoms and disorder are experienced by a significant proportion of young people and have long-lasting deleterious effects. The aims of the current investigation were to examine the aetiology of depressive symptoms using a twin design. In particular to examine the effects of sex, age, maternal depression and anxiety symptoms and to examine the aetiology of high depression scores.

METHODS

Questionnaires were sent to the families of a population-based sample of twins aged between 8 and 17 years. Parents and children over the age of 11 were asked to complete the Mood and Feelings Questionnaire and Hospital Anxiety and Depression Scale (mothers only). Responses were obtained from 1463 families and data were analysed using genetic model fitting and DeFries and Fulker regression analysis.

RESULTS

Depressive symptoms, particularly when self-rated, were significantly genetically influenced. There was evidence of significant heterogeneity according to age, with shared environmental factors more important and genetic factors less important for children aged 8 to 10 than for adolescents aged 11 to 17 years. Some but not all of the shared environmental influences on parent-rated depressive symptoms were accounted for by maternal symptoms of depression and anxiety. There was a significant effect of gender for self-rated depressive symptoms. For boys, genetic factors were of greater importance and common environmental influences of less importance than for girls. Shared environmental effects had a substantial influence on high self-rated depression scores. Adolescents who scored highly on self-rated depression questionnaires experienced significantly more shared life events and their mothers had significantly higher internalising symptoms than adolescents who scoredwithin the normal range.

CONCLUSIONS

The results of this study add to the evidence that the aetiology of depressive symptoms differs by age, with genetic factors becoming more important from childhood to adolescence. Some but not all of the shared environmental effect observed for mother-rated depression scores is due to maternal depression and anxiety symptoms. For self-rated depressive symptoms, the importance of genetic and environmental factors may also differ by sex, with genetic influences more important for boys. The aetiology of high depression symptom scores, when self-rated, appears to differ from scores within the normal range in that shared environmental factors appear to be more important. Further research is needed to identify these shared environmental factors using longitudinal models that test genetic and environmental mediation.

The heritability of depressive symptoms: multiple informants and multiple measures

BACKGROUND

Earlier research suggests large rater differences in heritability estimates of children's depressive symptoms in the context of significant age and sex-limitation effects.

METHODS

With data from an ongoing, population-based twin-family study, we estimated genetic and environmental influences on children's depression with models allowing for sex-specific effects. Our assessments of twins included self-reports and ratings made by their classmate peers, their parents and their teachers, allowing estimates of genetic and environmental effects with data from different informants. Model-fitting used maximum likelihood estimation of log-transformed data from a sample of 1,366 11- and 12-year-old twin pairs.

RESULTS

Estimates of additive genetic effects were significant for both boys and girls across all four informants, and, standardized to reflect the percentage of phenotypic variance accounted for, those estimates ranged from .28 to .71. Significant effects from common environmental sources were found in ratings of teachers and parents, where, typically, one individual rated both co-twins, but neither in peer nominations nor self-ratings. The correlation of teacher and parent ratings was modest, and bivariate model-fitting found no correlation in either genetic or shared environmental effects between teacher and parental ratings. At this young age, sex-limitation effects were found only in teacher ratings, where genetic effects were greater in girls than in boys.

CONCLUSIONS

Results underscore the utility of using multiple informants to measure children's behavior and provide a foundation for follow-up of these twins in later adolescence.

The genetic aetiology of childhood depression: a review

BACKGROUND

We review the evidence for the familiality of major depressive disorder (MDD) and the genetic aetiology of depressive symptoms in children and adolescents.

METHODS

Databases and reference lists were searched for family, twin and adoption studies of childhood MDD and childhood depressive symptoms. Data from independent family studies that fulfilled specified inclusion criteria were pooled and odds ratios were calculated for top-down and bottom-up family studies.

RESULTS

Estimates of familial risk differ by control group and by study design (odds ratio range 1.70, 3.98). Twin studies show that depressive symptoms in young people are heritable although rater and measurement issues are important. Adoption studies show little evidence for a genetic influence on depressive symptoms.

CONCLUSIONS

MDD in young people is familial although control group and study design affect the magnitude of the familial risk. Estimates of heritability from twin and adoption studies vary widely and few firm conclusions can be made regarding the genetic aetiology of depressive symptoms in childhood. Areas that require future work include the examination of rater effects, measurement issues, the effects of age and comorbidity and reasons for the discrepancy between twin and adoption findings.

Genetic and environmental contributions to loneliness in children

This report presents the results of the first behavioral genetic studies of children's loneliness. Data were collected using both an adoption design and a twin-sibling design. As part of the Colorado Adoption Project, 133 sibling pairs (69 biologically related pairs and 64 unrelated pairs in adoptive families) completed a general loneliness scale when they were 9, 10, 11, and 12 years old. As part of the San Diego Sibling Study, 142 sibling pairs (22 monozygotic twin, 40 dizygotic twin, and 80 full-sibling pairs) between the ages of 8 and 14 years old completed a scale assessing loneliness at school. Both studies showed significant heritability and nonshared environmental influences for children's loneliness.

Specific life events and chronic experiences differentially associated with depression and anxiety in young twins

Behavioral genetic analyses indicate that environmental influences associated with depression and anxiety are specific to each symptom type; however, this has not been tested specifically in children. Sixty-one (61) child twin pairs in which at least one twin had a very high anxiety or depression score, and 29 nonanxious, nondepressed pairs were interviewed about life events and chronic stressors in the previous 12 months. Loss events, schoolwork stressors, family relationship problems, and friendship problems were all significantly associated with depression but not anxiety. Threat events were significantly associated with anxiety but not depression. Loss events and schoolwork stressors appeared to act as shared environment influences in that they made twin pairs resemble one another. Threat events, friendship problems, and family relationship problems were individual specific and accounted for differences within the pairs. These results clarify the associations between life events and depressive and anxious symptoms in children and adolescents and reveal specific associations previously unidentified in this age range.

Using genetic analyses to clarify the distinction between depressive and anxious symptoms in children

Self-report measures of depression and anxiety in children are highly correlated and distinguishing between shared and independent factors in their etiologies is therefore problematic. The aim of this article was to test whether less correlated measures of depression and anxiety could be produced and, if so, what genetic and environmental factors would account for the variance in these symptoms. Second-order factor analysis of the items from two standardized self-report questionnaires of depression and anxiety collected from 395 pairs of same-sex twins aged 8 to 16 years resulted in purer dimensions of depression and anxiety. Behavioral genetic analyses confirmed the distinction between these two dimensions, and bivariate analyses revealed that the association between the two was primarily accounted for by shared genetic factors.

Behavioral genetics as a tool for developmental psychology: anxiety and depression in children and adolescents

Over the past decade there has been a huge increase in the number of behavioral genetic studies looking into anxiety and depression in children and adolescents. There are now enough data in this area to make a review of the results useful. This paper begins with an outline of the methods used in such research and moves on to review the results in extant studies. Overall, these studies indicate modest to moderate genetic influence on both anxiety and depression. However, behavioral genetic methods are also paramount for exploring environmental influences in addition to genetic influences. Shared environment (that which makes family members resemble one another) is rarely identified in adult studies of personality or psychopathology and does not appear to be a significant influence for depression but it is for anxiety. Nonshared environment, which makes family members differ from one another, is found to be a significant influence for both anxiety and depression. Patterns within these results due to rater effects, age effects, sex effects, the precise phenotype measured, and the study design are explored.