Semicircular canal size constrains vestibular function in miniaturized frogs.

Miniaturization has evolved repeatedly in frogs in the moist leaf litter environments of rainforests worldwide. Miniaturized frogs are among the world's smallest vertebrates and exhibit an array of enigmatic features. One area where miniaturization has predictable consequences is the vestibular system, which acts as a gyroscope, providing sensory information about movement and orientation. We investigated the vestibular system of pumpkin toadlets, Brachycephalus (Anura: Brachycephalidae), a clade of miniaturized frogs from Brazil. The semicircular canals of miniaturized frogs are the smallest recorded for adult vertebrates, resulting in low sensitivity to angular acceleration due to insufficient displacement of endolymph. This translates into a lack of postural control during jumping in Brachycephalus and represents a physical constraint resulting from Poiseuille's law, which governs movement of fluids within tubes.

Current parental depression and offspring perceived self-competence: a quasi-experimental examination.

A genetically-informed, quasi-experimental design was used to examine the genetic and environmental processes underlying associations between current parental depressive symptoms and offspring perceived self-competence. Participants, drawn from a population-based Swedish sample, were 852 twin pairs and their male (52 %) and female offspring aged 15.7 ± 2.4 years. Parental depressive symptoms were measured using the Center for Epidemiological Studies Depression scale. Offspring perceived self-competence was measured using a modified Harter Perceived Competence Scale. Cousin comparisons and Children of Twins designs suggested that associations between maternal depressive symptoms and offspring perceived self-competence were due to shared genetic/environmental liability. The mechanism responsible for father-offspring associations, however, was independent of genetic factors and of extended family environmental factors, supporting a causal inference. Thus, mothers and fathers may impact offspring perceived self-competence via different mechanisms and unmeasured genetic and environmental selection factors must be considered when studying the intergenerational transmission of cognitive vulnerabilities for depression.

Higher-order genetic and environmental structure of prevalent forms of child and adolescent psychopathology.

CONTEXT: It is necessary to understand the etiologic structure of child and adolescent psychopathology to advance theory and guide future research. OBJECTIVE: To test alternative models of the higher-order structure of etiologic effects on 11 dimensions of child and adolescent psychopathology using confirmatory factor analyses of genetic and environmental covariances. DESIGN: Representative sample of twins. SETTING: Home interviews. PARTICIPANTS: A total of 1571 pairs of 9- to 17-year-old twins. MAIN OUTCOME MEASURES: Structured assessments of psychopathology using adult caregivers and youth as informants. RESULTS: The best-fitting genetic model revealed that most genetic factors nonspecifically influence risk for either all 11 symptom dimensions or for dimensions of psychopathology within 1 of 2 broad domains. With some notable exceptions, dimension-specific genetic influences accounted for modest amounts of variance. CONCLUSIONS: To inform theory and guide molecular genetic studies, an etiologic model is offered in which 3 patterns of pleiotropy are hypothesized to be the principal modes of genetic risk transmission for common forms of child and adolescent psychopathology. Some common environmental influences were found, but consistent with a "generalist genes, specialist environments" model, there was little sharing of environmental influences. This implies that prevalent dimensions of child and adolescent psychopathology mostly share their genetic liabilities but are differentiated by nonshared experiences.

The etiology of associations between negative emotionality and childhood externalizing disorders.

Despite consistent documentation of associations between childhood negative emotionality and externalizing psychopathology, few genetically informative studies have investigated the etiology of that association. The goal of the current study was to delineate the etiology of the covariation of negative emotionality and childhood externalizing problems (e.g., oppositional defiant disorder, conduct disorder, inattention, and hyperactivity/impulsivity). Twin families were recruited from Georgia state birth records and completed parental report questionnaires of negative emotionality and common Diagnostic and Statistical Manual of Mental Disorders (4th ed., text rev.; American Psychiatric Association, 2000) child psychiatric disorders. Results suggest both genetic and environmental influences underlying negative emotionality and each externalizing symptom dimension, with additional evidence for sibling competition/rater contrast effects for inattention and hyperactivity/impulsivity. Bivariate model-fitting analyses indicated that a portion of the additive (43%-75%) and nonadditive (26%-100%) genetic influences underlying each symptom dimension was accounted for by the genetic influences underlying negative emotionality. Finally, an independent pathways model examining the etiology of the association between negative emotionality and the externalizing dimensions indicated that a substantial portion of the additive genetic, nonadditive genetic, and nonshared environmental influences underlying externalizing behavior is shared with negative emotionality.

Familial confounding of the association between maternal smoking during pregnancy and offspring criminality: a population-based study in Sweden.

CONTEXT: The association between maternal smoking during pregnancy (SDP) and offspring disruptive behaviors has been well documented, but it is unclear whether exposure to SDP or the effects of factors correlated with SDP account for the increased risk. OBJECTIVE: To test whether the association between SDP and offspring criminal convictions was consistent with a causal connection or due to familial background factors by controlling for measured covariates and using a quasi-experimental approach. DESIGN: We used a population-based study of children born in Sweden from 1983 to 1989 (N = 609,372) to examine the association between SDP and offspring criminal convictions while controlling for measured traits of both parents. We also compared siblings differentially exposed to SDP (n = 50,339) to account for unmeasured familial factors that could account for the association. SETTING: Population-based study of all children born in Sweden from 1983 to 1989 with information on maternal SDP and offspring criminal convictions based on national registries collected by the Swedish government. PATIENTS OR OTHER PARTICIPANTS: Children born in Sweden from 1983 to 1989 (N = 609,372) and siblings differentially exposed to SDP (n = 50,339). MAIN OUTCOME MEASURES: Violent and nonviolent convictions, based on the Swedish National Crime Register, a register with detailed information on all convictions in the country. RESULTS: Moderate (hazard rate [HR], 2.47; 95% confidence interval [CI], 2.34-2.60) and high (HR, 3.43; 95% CI, 3.25-3.63) levels of maternal SDP were associated with an increased risk for offspring violent convictions, even when controlling for maternal and paternal traits. There was no association between SDP and violent convictions, however, when comparing differentially exposed siblings (HR(moderate), 1.02; 95% CI, 0.79-1.30; HR(high), 1.03; 95% CI, 0.78-1.37). Smoking during pregnancy also was associated with nonviolent convictions in the entire population (HR(moderate), 1.62; 95% CI, 1.58-1.66; HR(high), 1.87; 95% CI, 1.82-1.92) and when controlling for covariates. But, there was no association when comparing siblings who were differentially exposed (HR(moderate), 0.89; 95% CI, 0.78-1.01; HR(high), 0.89; 95% CI, 0.78-1.02). CONCLUSION: The results suggest that familial background factors account for the association between maternal SDP and criminal convictions, not the specific exposure to SDP.

A quasi-experimental study of maternal smoking during pregnancy and offspring academic achievement.

The current study, based on all births in Sweden from 1983 to 1991 (N = 654,707), explored the processes underlying the association between smoking during pregnancy (SDP) and offspring school grades and mathematic proficiency at age 15. The analyses compared relatives who varied in their exposure to SDP and who varied in their genetic relatedness. Although SDP was statistically associated with academic achievement (AA) when comparing unrelated individuals, the results suggest that SDP does not cause poorer academic performance, as full siblings differentially exposed to SDP did not differ in their academic scores. The pattern of results suggests that genetic factors shared by parents and their offspring help explain why offspring exposed to SDP have lower levels of AA.