Internalizing and externalizing problems across childhood and psychotic-like experiences in young-adulthood: The role of developmental period.

BACKGROUND Psychopathology in childhood and adolescence, commonly indexed by co-occurring internalizing and externalizing problem behaviors, has been found to predict psychotic-like experiences (PLEs) in adults. However, studies to date have rarely examined internalizing and externalizing problem behaviors simultaneously or identified in which developmental period do these problem behaviors predict PLEs in adults. This study tests to what extent internalizing and externalizing problem behaviors in childhood (4-9 years) or adolescence (11-16 years) predict PLEs in young-adulthood (18 years). METHODS Parent-rated child internalizing and externalizing problems on the Strengths and Difficulties Questionnaire at ages 4, 6, 8, 9, 11, 13, and 16 years from the Avon Longitudinal Study of Parents and Children (N = 4717) were modelled using two-piece latent growth curve modelling to predict clinician-rated PLEs at age 18 years, controlling for confounders (gender, ethnicity, socio-economic status, parental education and stressful life events) assessed prior to baseline at age 4 years. RESULTS Controlling for confounders, an increase in childhood internalizing problems from 4 to 9 years and externalizing problems at baseline (at 4 years) predicted PLEs at 18 years, explaining 9.5% of the variance in adult PLEs. These associations were independent to controls for any changes in adolescent internalizing and externalizing problems from 11 to 16 years. CONCLUSIONS High baseline levels of externalizing problems and increasing internalizing problems throughout childhood can predict PLEs at 18 years. Externalizing problems around the transition to primary school and internalizing problems throughout childhood may be particularly helpful in informing risk of PLEs in young-adulthood.