Background: We consider the evidence for the proposition that the early phase of psychosis (including the period of untreated psychosis) is a critical period in which (a) long-term outcome is predictable, and (b) biological, psychological and psychosocial influences are developing and show maximum plasticity.
Method: First-episode prospective studies, predictors of outcome and the genesis of patients' key appraisals of their psychosis are reviewed.
Results: The data support the notion of the 'plateau effect', first coined by Tom McGlashan, which suggested that where deterioration occurs, it does so aggressively in the first 2-3 years; and that critical psychosocial influences, including family and psychological reactions to psychosis and psychiatric services, develop during this period.
Conclusions: The early phase of psychosis presents important opportunities for secondary prevention. We outline a prototype of intervention appropriate to the critical period. The data challenge the widely held assumption that first-episode psychosis is a benign illness posing little risk.