Beyond the critical period: longitudinal study of 8-year outcome in first-episode non-affective psychosis

Background The critical period hypothesis proposes that deterioration occurs aggressively during the early years of psychosis, with relative stability subsequently. Thus, interventions that shorten the duration of untreated psychosis (DUP) and arrest early deterioration may have long-term benefits. Aims To test the critical period hypothesis by determining whether outcome in non-affective psychosis stabilises beyond the critical period and whether DUP correlates with 8-year outcome; to determine whether duration of untreated illness (DUI) has any independent effect on outcome. Method We recruited 118 people consecutively referred with first-episode psychosis to a prospective, naturalistic cohort study. Results Negative and disorganised symptoms improved between 4 and 8 years. Duration of untreated psychosis predicted remission, positive symptoms and social functioning at 8 years. Continuing functional recovery between 4 and 8 years was predicted by DUI. Conclusions These results provide qualified support for the critical period hypothesis. The critical period could be extended to include the prodrome as well as early psychosis.