Prenatal substance exposure, adverse childhood experiences and diagnosed mental and behavioral disorders - A longitudinal register-based matched cohort study in Finland.

Both prenatal substance exposure (PSE, alcohol/drugs) and experiences during the first years of life have powerful effects on brain development. However, only a few studies have investigated the combined effect of PSE and adverse childhood experiences (ACEs) on mental and behavioral disorders among exposed adolescents and adults. This longitudinal register-based cohort study 1) compared the nature and extent of diagnosed mental and behavioral disorders among youth with PSE and matched unexposed controls, and 2) investigated the influence of PSE, health in infancy and ACEs (maternal risk factors and out-of-home care, OHC) on diagnoses of mental and behavioral disorders. The data consisted of 615 exposed youth aged 15-24 years and 1787 matched unexposed controls. Data from hospital medical records and nine registers were merged for the analysis. Descriptive analysis methods and Cox regression were used. The results showed that the prevalence of mental and behavioral disorders was twice as high among exposed compared with controls. The highest levels of mental and behavioral disorders and ACEs were found among exposed with at least one OHC episode. The difference in the risk of mental and behavioral disorders between exposed and controls diminished after controlling for the effect of ACEs. Low birth weight, maternal risk factors, and OHC were the strongest predictors of mental and behavioral disorders. The results suggest that PSE alone does not explain poorer mental health among exposed youth. Risk factors accumulate, and low birth weight and ACEs are strongly associated with increased risk of mental and behavioral disorders.