Evidence for a persistent, environment-dependent and deteriorating subtype of subclinical psychotic experiences: a 6-year longitudinal general population study.

BACKGROUND Research suggests that subclinical psychotic experiences during adolescence represent the behavioral expression of liability for psychosis. Little is known, however, about the longitudinal trajectory of liability in general population samples. METHOD Growth mixture modeling was used to examine longitudinal trajectories of self-reported positive psychotic experiences in the Youth Self Report (YSR), completed three times over a period of 6 years by a general population cohort of adolescents aged 10-11 years at baseline (n=2230). RESULTS Four groups with distinct developmental trajectories of low, decreasing, increasing and persistent levels of mild positive psychotic experiences were revealed. The persistent trajectory was associated strongly with cannabis use, childhood trauma, developmental problems and ethnic minority status, and consistently displayed strong associations with factors known to predict transition from subclinical psychotic experience to clinical psychotic disorder (severity of and secondary distress due to psychotic experiences, social and attentional problems and affective dysregulation) and also with high levels of parental-reported psychotic experiences and use of mental health care at the end of the follow-up period. Progressively weaker associations were found for the increasing, decreasing and low trajectories respectively. CONCLUSIONS The results suggest that the outcome of early developmental deviation associated with later expression of psychotic experiences is contingent on the degree of later interaction with environmental risks inducing, first, persistence of psychotic experiences and, second, progression to onset of need for care and service use. Insight into the longitudinal dynamics of risk states in representative samples may contribute to the development of targeted early intervention in psychosis.