Overview

Current antipsychotic treatments of schizophrenia are only partially effective, and their use is often associated with serious side effects. Cannabidiol is a natural counterpart of the psychoactive component of marijuana, delta-9- tetrahydrocannabinol and has no psychotomimetic or addictive properties. In a controlled clinical trial of cannabidiol versus amisulpride in acute paranoid schizophrenia we showed a statistically significant clinical improvement in all symptoms clusters of schizophrenia compared to baseline with either treatment. Cannabidiol displayed a significantly superior side-effect profile in particular regarding prolactin elevation, extrapyramidal symptoms and weight gain. The favorable side-effect profile and potentially novel mechanism of action identify this molecule as a potential antipsychotic. However, long-term safety and efficacy data is still lacking. This study is to evaluate the efficacy and safety of the novel compound cannabidiol in the maintenance treatment of schizophrenia in comparison to placebo as an add-on to an established treatment with either amisulpride, aripiprazole, olanzapine, quetiapine or risperidone, in a 12-months, double-blind, parallel-group, randomized, placebo-controlled clinical trial. Thereby, relevant data on cannabidiol's antipsychotic potential will be gained.

Eligibility

Inclusion Criteria:

• Informed consent given by the subject
• DSM-IV-TR diagnosis of schizophrenic psychosis (295.10-30, 295.90)
• First documented diagnosis of schizophrenia must not be no older than seven years.
• Patients must receive a stable dose of amisulpride, aripiprazole, olanzapine, quetiapine or risperidone (TAU: treatment as usual) at least 4 weeks prior to inclusion in the study to ensure that the maximal effect of the previous medication has been received.
• Initial PANSS total score of ≤ 75 at baseline.
• proper contraception in female patients of childbearing potential
• body mass index between 18 and 40.

Exclusion Criteria:

• Lack of accountability
• positive urine drug-screening for illicit drugs at screening (except cannabinoids and benzodiazepines)
• serious suicidal risk at screening visit
• other relevant interferences of axis 1 according to diagnostic evaluation (MINI) including residual forms of schizophrenia.
• other relevant neurological or other medical disorders
• pregnancy or lactation.