Cognitive ability following exposure to parental mental disorders and other childhood adversities: a population-based cohort study of Danish males in late adolescence.

UNLABELLED: The purpose of the study is to examine the association between parental mental disorders diagnosed before age six and cognitive ability at age 18, using data from a population-based cohort of male adolescents attending military conscription. Further, we tested whether other childhood adversities modified this association. All males born in Denmark 1996-2001 were linked to national registers. Parental mental disorders were identified from psychiatric hospital diagnoses. We assessed other childhood adversities before age six, including family health-related, socioeconomic, and family instability, as well as the number of adversities experienced. Cognitive scores from the mandatory military conscription were standardized (mean 100, SD = 15). Associations were estimated using multiple linear regression, and effect modification was evaluated using Wald tests. We included 125,791 males (mean age 18 years, SD = 0.66), of whom 6708 had a parent with a mental disorder. Parental mental disorders were associated with a 0.91-point reduced cognitive ability score (95% confidence interval - 1.3, - 0.53). This association was not observed in adolescents who lived with only one parent (- 0.35 (- 0.85, 0.15)), those placed in out-of-home care (3.2 (0.59, 5.8)), and those with ≥ 3 additional adversities before age six. Effect modification tests were statistically significant for these groups (p < 0.01).

CONCLUSION: Parental mental disorders before age six were associated with a modest reduction in cognitive ability in males at age 18, compared with those without parental mental disorders. Our findings show the association varies across family contexts, although unmeasured genetic and environmental confounding should be considered in interpreting these results.

WHAT IS KNOWN: • Parental mental disorders are common and linked to lower cognitive ability in offspring. • Childhood adversities often cluster within families and are associated with poorer cognitive outcomes.

WHAT IS NEW: • In this nationwide Danish cohort, parental mental disorders before age six were associated with slightly lower cognitive ability at age 18. • This association was not observed among adolescents with > 2 additional adversities, those who lived with only one parent, or those placed in out-of-home care before age six, suggesting the association varies across family context.