Intention of the study is to examine, if the symptomatology of dual diagnosis patients is less severe after a special indication training for reduction of cannabis consumption in comparison to unspecified trainings.

Point of interest is psychopathology and consumerism.

Dual diagnosis patients (psychosis and cannabis abuse) account for more clinical admissions than single diagnosis patients.

Cannabis misuse is a known risk factor for recurrence of psychosis.

A specified intervention on the basis of a manual for schizophrenic substance abusers is administered to inpatients in a specialized unit for young schizophrenic patients in a psychiatric hospital.

The control group, same indication (psychotic disorder and cannabis misuse) receives social competence training (specified for schizophrenic patients as well).

Admission to groups is randomly.

Inclusion Criteria:

• Clinical diagnosis of schizophrenia and disorders with psychotic features
• Misuse of cannabis during 12 months preceding admission to hospital

Exclusion Criteria:

• Not able to attend training twice a week for 45 minutes (concentration, attention, psychotic symptoms, agitation)
• Discharge from hospital before completion of training