Negative effects of paternal age on children's neurocognitive outcomes can be explained by maternal education and number of siblings.

BACKGROUND: Recent findings suggest advanced paternal age may be associated with impaired child outcomes, in particular, neurocognitive skills. Such patterns are worrisome given relatively universal trends in advanced countries toward delayed nuptiality and fertility. But nature and nurture are both important for child outcomes, and it is important to control for both when drawing inferences about either pathway. METHODS AND FINDINGS: We examined cross-sectional patterns in six developmental outcome measures among children in the U.S. Collaborative Perinatal Project (n = 31,346). Many of these outcomes at 8 mo, 4 y, and 7 y of age (Bayley scales, Stanford Binet Intelligence Scale, Graham-Ernhart Block Sort Test, Wechsler Intelligence Scale for Children, Wide Range Achievement Test) are negatively correlated with paternal age when important family characteristics such as maternal education and number of siblings are not included as covariates. But controlling for family characteristics in general and mother's education in particular renders the effect of paternal age statistically insignificant for most developmental measures. CONCLUSIONS: Assortative mating produces interesting relationships between maternal and paternal characteristics that can inject spurious correlation into observational studies via omitted variable bias. Controlling for both nature and nurture reveals little residual evidence of a link between child neurocognitive outcomes and paternal age in these data. Results suggest that benefits associated with the upward trend in maternal education may offset any negative effects of advancing paternal age.

Mothers' transitions from welfare to work and the well-being of preschoolers and adolescents.

Results from a longitudinal study of 2402 low-income families during the recent unprecedented era of welfare reform suggest that mothers' transitions off welfare and into employment are not associated with negative outcomes for preschoolers (ages 2 to 4 years) or young adolescents (ages 10 to 14 years). Indeed, no significant associations with mothers' welfare and employment transitions were found for preschoolers, and the dominant pattern was also of few statistically significant associations for adolescents. The associations that did occur provided slight evidence that mothers' entry into the labor force was related to improvements in adolescents' mental health, whereas exits from employment were linked with teenagers' increased behavior problems.