It has been hypothesized that the first five years after first episode of psychosis constitutes a critical period in with opportunities for ameliorating the course of illness. Based on this rationale, specialized assertive early intervention services were developed. We wanted to investigate the evidence basis for such interventions.

The evidence for the effectiveness of specialized assertive early intervention services is mainly based on one large randomized clinical trial, the OPUS trial, but it is supported by the findings in smaller trials such as the Lambeth Early Onset (LEO) trial, the Croydon Outreach and Assertive Support Team COAST trial and the Norwegian site of Optimal Treatment (OTP) trial. There are positive effects on psychotic and negative symptoms, on substance abuse and user satisfaction, but the clinical effects are not sustainable when patients are transferred back to standard treatment. However the positive effects on service use and ability to live independently seem to be durable.

Implementation of specialized assertive early intervention services is recommended, but the evidence basis needs to be strengthened through replication in large high quality trials. Recommendation regarding the duration of treatment must await results of ongoing trials comparing two years of intervention with extended treatment periods.