Cannabidiol for Treatment of Non-affective Psychosis and Cannabis Use

People with psychosis and comorbid cannabis use are particularly difficult to treat because cannabis use worsens psychotic symptoms and increases the risk that a first-episode psychosis will progress to schizophrenia. It is the THC (tetrahydrocannabinol) content in cannabis that aggravates psychotic symptoms whereas the CBD content has potential therapeutic effects. This trial investigates treatment with CBD (without THC) versus risperidone (an antipsychotic agent) in people with psychosis and lifetime use of cannabis. We hypothesize that CBD will ameliorate psychotic symptoms and reduce the frequency of cannabis use to a larger extent than risperidone. Sleep disturbances are often a limiting factor in the treatment of psychosis, and it is also examined how CBD affects objective and subjective sleep quality as well as circadian rest-activity cycles. Based on previous studies investigating CBD as monotherapy in patients with schizophrenia, it is expected that CBD will be associated with fewer adverse events than risperidone.