Abstract
Background There has been considerable recent interest in possible causal linkages between exposure to bullying victimization and later psychotic symptomatology. Prior research in this area has had several limitations which make it difficult to ascertain causality, and to determine the extent to which these effects extend beyond adolescence. Method Data were obtained from the Christchurch Health and Development Study, a 35-year study of a longitudinal birth cohort. This investigation used generalized estimating equation modelling to estimate the associations between bullying victimization (ages 13-16 years) and psychotic symptoms (ages 18-35 years), before and after controlling for possible confounding factors, including: gender; childhood socio-economic status; child intelligence quotient; exposure to sexual abuse in childhood; anxious/withdrawn behaviour and attention problems (ages 7-9 years); and adolescent psychotic symptoms and paranoid ideation (ages 15-16 years). Results There was a significant (p < 0.0001) bivariate association between bullying victimization in adolescence and psychotic symptomatology in adulthood. Successive models controlling for covariation reduced this association to statistical non-significance. After controlling for covariates, those with the highest level of bullying victimization had rates of psychotic symptoms that were 1.21 (95% confidence interval 0.73-1.99) times higher than those who were not victimized. Conclusions The association between bullying victimization in adolescence and psychotic symptomatology in adulthood could be largely explained by childhood behavioural problems, and exposure to sexual abuse in childhood. The results suggest that bullying victimization was unlikely to have been a cause of adult psychotic symptoms, but bullying victimization remained a risk marker for these symptoms.