Prenatal smoking and child psychopathology associations by age and sex in the ECHO cohort.

Maternal tobacco smoking during pregnancy (MSDP) is associated with an increased risk of child externalizing problems. It remains unclear whether these associations are externalizing-specific, or better explained by comorbidity between externalizing and internalizing domains, or vary by age and sex. To address comorbidity and differentiation between domains, we leveraged the severity-directional model of psychopathology. Severity reflects the overall level of psychopathology symptoms across both domains (high levels of severity can only be reached by having symptoms of both types simultaneously), whereas directionality captures the balance/differentiation of internalizing vs. externalizing symptoms regardless of number of total symptoms. Participants included 16,335 children aged 1-19 years old (47.78% female, 58.17% White, 75.46% non-Hispanic) from 55 U.S.-based cohorts within the Environmental Influences on Child Health Outcomes (ECHO) consortium. MSDP predicted differentiation toward externalizing problems in 2-year age bins 1-2 through 7-8 and 13-14 years; remaining (non-significant) age bins had similar magnitudes. MSDP predicted higher symptom severity in all age bins. Findings likely reflect a combination of MSDP associations with comorbid symptom severity and specificity toward externalizing problems, with little evidence of age or sex differences. Additional analyses explored e-cigarette use, other prenatal substance use, and postnatal smoke exposure; associations were sparse and unsystematic.