The main objective of the trial is to evaluate, how long an antipsychotic relapse-prevention should be continued and to which time a patient with schizophrenia is protected enough, so that a withdrawal or reduction of the medication seems appropriate. Relapse is defined as primary outcome.

The main objective of the trial is to evaluate for the first time, how long an antipsychotic relapse-prevention should be continued and to which time a patient is protected enough, so that a guided withdrawal or reduction of the medication seems appropriate. Relapse is defined as primary outcome. We include patients with schizophrenia or schizoaffective disorder in remission for at least 3 years under a stable antipsychotic medication.

Inclusion Criteria:

• Diagnosis of schizophrenia or schizoaffective disorder
• The participants have to be in remission for at least 3 years (i.e. no psychiatric hospitalisation) under a stable antipsychotic medication. Remission will be measured using the remission criteria by Andreasen et al. (2005) Score ≤3 for the items concerning psychosis of the "Positive and Negative Syndrom Scale" (PANSS; Kay et al., 1987): "Delusions" (P1), "Conceptual disorganisation" (P2), "Halluzinations" (P3), "Mannerisms and posturing" (G5) and "Unusual thought content" (G9) and a score ≤3 on the "Clinical Global Impression Severity Scale" (CGI-S; Guy, 1976)
• Able to give informed consent

Exclusion Criteria:

• Actively suicidal
• Serious medical illnesses
• Known non-complience concerning the medication
• Medication with clozapin
• Medication with antidepressants and mood stabilisors that were initiated during the last 6 weeks before study enrollment
• Patients with substance dependence other than nicotine or caffeine within 6 months prior to baseline
• Unability to give informed consent
• Pregnancy