Observed externalizing behavior: a developmental comparison of genetic and environmental influences across three samples

Informant similarities, twin studies, and the assessment of externalizing behavior: A meta-analysis

The purpose of this study was to examine similarity within informant ratings of the externalizing behavior of monozygotic (MZ) and dizygotic (DZ) twin pairs. To do this, we conducted a meta-analysis of correlations within ratings completed by mothers, fathers, teachers, and youth. We retrieved n=204 correlations for MZ twins and n=267 correlations for DZ twins from n=54 studies containing n=55 samples. Results indicated that all four informants were significant negative predictors of within-informant correlations in their ratings of MZ, but not DZ twins. In the case of longitudinal studies and as the age of MZ twins increased, similarity within ratings by mothers was significantly greater than similarity within ratings by fathers. Among participant characteristics, we found that (a) age was a significant negative predictor of similarity within ratings for MZ twins; (b) race was a significant predictor of similarity within ratings for both MZ and DZ twins, but in the opposite direction; and (c) DZ opposite sex twins were a significant negative predictor of within-rating similarity. Among study characteristics for MZ twins, participant group and longitudinal study were significant negative predictors of within-rating similarity, and for both MZ and DZ twin pairs, non-independence in the data was a significant negative predictor of within-rating similarity. For DZ twins, multiple informants were significant positive predictors of within-rating similarity, and in longitudinal studies with DZ twins, similarity within ratings by mothers was significantly greater than similarity within ratings by fathers, and similarity within ratings by fathers was significantly less than similarity within ratings by teachers and youth. For both MZ and DZ twins, the following study characteristics were significant positive predictors of similarity within ratings: study group, number of time points, and multiple constructs. All four informants appeared equally skilled at predicting within-informant correlations for MZ (but not DZ) twins, with participant characteristics having different predictive effects for MZ compared to DZ twins, and study characteristics having comparable predictive effects for both twin types. Overall, these findings suggest effective discrimination on the part of four informants who rated the externalizing behavior of MZ and DZ twins.

Pubertal maturation and affective symptoms in adolescence and adulthood: Evidence from a prospective birth cohort

The higher prevalence of affective symptoms among women compared to men emerges in adolescence, and it has been associated with pubertal maturation. However, it remains unclear whether pubertal timing has long-term influences on affective symptoms. Using data from the British 1946 birth cohort, we investigated whether pubertal timing was associated with affective symptoms over the life course, distinguishing those with symptoms in adolescence only, symptoms in adulthood only, and symptoms in both adolescence and adulthood. In females, there was no evidence that early pubertal maturation was a risk factor for affective symptoms. However, those with particularly late menarche (≥15 years) showed a lower risk of adult-onset affective symptoms (odds ratio = 0.54, 95% confidence interval = 0.31, 0.95). This effect of late pubertal timing was not explained by a range of sociobehavioral factors. In contrast, in males, late pubertal timing was associated with increased risk of adolescent-onset affective symptoms that tracked into adulthood (odds ratio = 2.10, 95% confidence interval = 1.44, 3.06). This effect was partly explained by low prepubertal body mass index. Sex-specific effects of pubertal timing on the long-term risk of affective symptoms might be due to different effects of gonadal hormonal on the central nervous system, as well as different social experiences during puberty.

Etiological heterogeneity of symptom dimensions of adolescent depression

The aim was to investigate the underlying factor structure of adolescent depression and etiological heterogeneity in the symptom dimensions of adolescent depression. The sample included 842 pairs of same-sex adolescent twins, among which 613 pairs were monozygotic twins and 229 pairs were dizygotic twins. The ages of the participants ranged from 11 to 17 years (M = 13.64, SD = 1.80). Adolescents' depressive symptoms were assessed using the self-reported Children's Depression Inventory. Exploratory and confirmatory factor analyses were used to explore the factor structure of youth depression and twin genetic analyses were employed to estimate genetic and environmental influences on the derived dimensions. Results showed that adolescent depression encompassed five correlated dimensions: dysphoria mood, somatic symptoms, study and externalizing problems, anhedonia symptoms, and cognitive symptoms. These five symptom dimensions had heterogeneous etiologies: Dysphoria mood, somatic symptoms, and cognitive symptoms were moderately heritable (heritability ranged from 33 to 40%), whereas study and externalizing problems, and anhedonia symptoms were mainly environmentally influenced with minimal genetic basis. Our findings supported the multidimensionality of adolescent depression and the etiological heterogeneity of these symptom dimensions.

The Michigan State University Twin Registry (MSUTR): an update

The primary aim of the Michigan State University Twin Registry (MSUTR) is on understanding developmental changes in genetic, environmental, and neurobiological influences on internalizing and externalizing disorders, with antisocial behavior and disordered eating representing our particular areas of interest. The MSUTR has two broad components: a large-scale, population-based registry of child, adolescent, and adult twins and their families (current N ~20,000) and a series of more focused and in-depth studies drawn from the registry (current N ~4,000). Participants in the population-based registry complete a family health and demographic questionnaire via mail. Families are then recruited for one or more of the intensive, in-person studies from the population-based registry based on their answers to relevant items in the registry questionnaire. These in-person assessments target a variety of biological, genetic, and environmental phenotypes, including multi-informant measures of psychiatric and behavioral phenotypes, census and neighborhood informant reports of twin neighborhood characteristics, buccal swab and salivary DNA samples, assays of adolescent and adult steroid hormone levels, and/or videotaped interactions of child twin families. This article provides an overview of the MSUTR and describes current and future research directions.

Psychological differences between smokers who spontaneously quit during pregnancy and those who do not: a review of observational studies and directions for future research

INTRODUCTION

Although remarkable interindividual differences among pregnant smokers' decision/ability to quit have been documented, the psychological factors that may account for these differences have received less attention and comprised the primary aim of this review.

METHODS

We searched the medical and behavioral sciences literature from 1996 to November 2011 using PubMed and PsycINFO(®). Fifty-one articles were identified based on titles or abstracts. These articles were reviewed in full and searched for quantitative observational studies of population-based or clinical samples, with the main topic of comparing smokers who quit spontaneously during pregnancy with those who did not, utilizing multivariable analyses.

RESULTS

The eight pertinent studies reviewed herein included four longitudinal studies and four cross-sectional analyses. Amidst significant variability among measures used, social support, depressive symptoms, and anxiety appeared unrelated to smoking cessation during pregnancy. Furthermore, when severity of nicotine dependence was controlled, maternal history of attention-deficit/hyperactivity disorder, depression, bipolar disorder, and schizophrenia all showed no independent relationship with smoking cessation during pregnancy, whereas maternal history of conduct disorder did. Secure attachment, prosocial personality, self-esteem, and perceived parenting competence were additional predictors of cessation during pregnancy.

CONCLUSIONS

A greater understanding of psychological factors that differentiate smokers who spontaneously quit during pregnancy from those who do not is crucial to the design of more effective prenatal smoking cessation interventions and also may elucidate causal mechanisms that underlie the well-established link between maternal smoking during pregnancy and offspring behavioral problems. Directions for future research and public health and policy implications are discussed.

Confirming the etiology of adolescent acting-out behaviors: an examination of observer-ratings in a sample of adoptive and biological siblings

BACKGROUND

A recent meta-analysis revealed moderate shared environmental influences (C) on most forms of child and adolescent psychopathology (Burt, 2009), including antisocial behavior. Critically, however, the research analyzed in this meta-analysis relied largely on specific informant-reports (and particularly parent and child reports), each of which is subject to various sources of rater bias. Observer-ratings of children's behaviors avoid many of these biases, and are thus well suited to verify the presence of C. Given this, we sought to buttress the evidence supporting C in two key ways. First, we sought to confirm that C contributes to observer-ratings in a sample of adoptive siblings, as similarity between adoptive siblings constitutes a 'direct' estimate of C. Second, we sought to confirm that these shared environmental influences persist across informants (i.e., the effects are not specific to the rater or the context in question).

METHODS

The current study examined the etiology of observer-ratings of acting-out behaviors, as well as sources of etiological overlap across observer-ratings, adolescent self-report and maternal-report in sample of over 600 biological and adoptive sibling pairs from the Sibling Interaction and Behavior Study (SIBS).

RESULTS

Results revealed moderate and significant shared environmental influences on observer-ratings (31%), as well as on the other informant-reports (20-23%). Moreover, a portion of these effects overlapped across measures (C correlations ranged from .32 to .34).

CONCLUSIONS

Such findings argue against passive gene-environment correlations (rGE) and rater bias as primary explanations for earlier findings of C on antisocial behavior, and in this way, offer a critical extension of prior work indicating that the role of shared environmental influences on child and adolescent antisocial behavior was dismissed too soon.