Background During the last decades we have seen a new focus on early treatment of psychosis. Several reviews have shown that duration of untreated psychosis (DUP) is correlated to better outcome. However, it is still unknown whether early treatment will lead to a better long-term outcome. This study reports the effects of reducing DUP on 5-year course and outcome.Method During 1997â€"2000 a total of 281 consecutive patients aged >17 years with first episode non-affective psychosis were recruited, of which 192 participated in the 5-year follow-up. A comprehensive early detection (ED) programme with public information campaigns and low-threshold psychosis detection teams was established in one healthcare area (ED-area), but not in a comparable area (no-ED area). Both areas ran equivalent treatment programmes during the first 2 years and need-adapted treatment thereafter.Results At the start of treatment, ED-patients had shorter DUP and less symptoms than no-ED-patients. There were no significant differences in treatment (psychotherapy and medication) for the 5 years. Mixed-effects modelling showed better scores for the ED group on the Positive and Negative Syndrome Scale negative, depressive and cognitive factors and for global assessment of functioning for social functioning at 5-year follow-up. The ED group also had more contacts with friends. Regression analysis did not find that these differences could be explained by confounders.Conclusions Early treatment had positive effects on clinical and functional status at 5-year follow-up in first episode psychosis.