Testing Causal Effects of Maternal Smoking During Pregnancy on Offspring's Externalizing and Internalizing Behavior.

Maternal smoking during pregnancy (SDP) is associated with increased risk of externalizing and internalizing behaviors in offspring. Two explanations (not mutually exclusive) for this association are direct causal effects of maternal SDP and the effects of genetic and environmental factors common to parents and offspring which increase smoking as well as problem behaviors. Here, we examined the associations between parental SDP and mother rated offspring externalizing and internalizing behaviors (rated by the Child Behavior Checklist/2-3) at age three in a population-based sample of Dutch twins (N = 15,228 pairs). First, as a greater effect of maternal than of paternal SDP is consistent with a causal effect of maternal SDP, we compared the effects of maternal and paternal SDP. Second, as a beneficial effect of quitting smoking before pregnancy is consistent with the causal effect, we compared the effects of SDP in mothers who quit smoking before pregnancy, and mothers who continued to smoke during pregnancy. All mothers were established smokers before their pregnancy. The results indicated a greater effect of maternal SDP, compared to paternal SDP, for externalizing, aggression, overactive and withdrawn behavior. Quitting smoking was associated with less externalizing, overactive behavior, aggression, and oppositional behavior, but had no effect on internalizing, anxious depression, or withdrawn behavior. We conclude that these results are consistent with a causal, but small, effect of smoking on externalizing problems at age 3. The results do not support a causal effect of maternal SDP on internalizing behaviors.

Stability in symptoms of anxiety and depression as a function of genotype and environment: a longitudinal twin study from ages 3 to 63 years.

BACKGROUND: The influence of genetic factors on major depressive disorder is lower than on other psychiatric disorders. Heritability estimates mainly derive from cross-sectional studies, and knowledge on the longitudinal aetiology of symptoms of anxiety and depression (SxAnxDep) across the lifespan is limited. We aimed to assess phenotypic, genetic and environmental stability in SxAnxDep between ages 3 and 63 years. METHOD: We used a cohort-sequential design combining data from 49 524 twins followed from birth to age ⩾20 years, and from adolescence into adulthood. SxAnxDep were assessed repeatedly with a maximum of eight assessments over a 25-year period. Data were ordered in 30 age groups and analysed with longitudinal genetic models. RESULTS: Over age, there was a significant increase during adolescence in mean scores with sex differences (women>men) emerging. Heritability was high in childhood and decreased to 30-40% during adulthood. This decrease in heritability was due to an increase in environmental variance. Phenotypic stability was moderate in children (correlations across ages ~0.5) and high in adolescents (r = 0.6), young adults (r = 0.7), and adults (r = 0.8). Longitudinal stability was mostly attributable to genetic factors. During childhood and adolescence there was also significant genetic innovation, which was absent in adults. Environmental effects contributed to short-term stability. CONCLUSIONS: The substantial stability in SxAnxDep is mainly due to genetic effects. The importance of environmental effects increases with age and explains the relatively low heritability of depression in adults. The environmental effects are transient, but the contribution to stability increases with age.

[Early alcohol initiation and increased adult alcohol consumption: cause or indicator?]. / Vroege alcoholinitiatie en verhoogde alcoholconsumptie op volwassen leeftijd; oorzaak of indicator?

BACKGROUND: Early alcohol initiation is strongly associated with increased alcohol consumption and alcohol abuse/dependence in adulthood. The mechanisms that underlie this association are unclear. AIM: To examine whether there is a causal link between early alcohol initiation and later alcohol consumption. METHOD: Survey data were collected from twin pairs (age range 18-80) included in the Netherlands Twin Register (NTR). A discordant twin design was used to examine the origin of the link between early alcohol initiation and adult alcohol consumption. Within monozygotic pairs (82-143 pairs), twins who started drinking early were compared to their brother/sister who started drinking later, on frequency of alcohol use, weekly alcohol consumption, number of alcohol intoxications, excessive drinking, alcohol abuse/-dependence, and hazardous drinking. By drawing comparisons within monozygotic pairs, we were able to control for the effects of genes/shared environment. Additional analyses examined the effects of age, sex, and in-/exclusion of lifelong abstainers. RESULTS: Within monozygotic twin pairs, the twin who had started drinking early did not differ significantly from his/her brother/sister with respect to future alcohol consumption. Results were independent of age, sex, and in-/exclusion of lifelong abstainers. CONCLUSION: Early alcohol initiation did not have significant causal effects on subsequent alcohol consumption in adulthood and may be an indicator of a predisposition for alcohol consumption. Campaigns aimed at raising the minimum age for alcohol initiation will possibly have only a limited effect on adult alcohol consumption.

Oral health-related quality of life of children with craniofacial conditions.

OBJECTIVE: Evaluation of the Dutch Child Oral Health Impact Profile (COHIP), assessing the level of concordance between parents and children. The internal consistency and the predictive validity of the COHIP for self-reported general health were examined. METHODS: Sample size was 35 pairs of parents and children age 11 to 14 with craniofacial conditions. Cronbach alphas were calculated and the level of concordance between parents and children was studied using t tests and intraclass correlations. Predictive validity was assessed using Pearson correlations and linear regression analyses. RESULTS: The COHIP and its subscales, except for one, had satisfactory to high Cronbach alphas (.59 to .94). Parents and children did not differ significantly. Correlations between parents and children were high (.62 to .91). Only "Oral symptoms" proved to be a significant predictor of general health, but only in the parent sample. CONCLUSIONS: In spite of the high level of concordance found, proxy reports have to be considered complementary to the reports of the children themselves. The Dutch version of the COHIP performs adequately, but could use some further psychometric evaluation and revision. It does not seem advisable to use the subscales separately as predictors in the same regression model, since they are strongly intercorrelated. For use in craniofacial patients, further validation is needed on a larger sample and some items need to be revised or removed. Finally, given the small number of cases, conclusions must be drawn with caution.