The first investigation on the possible antipsychotic effects in humans was done in a schizophrenic patient who had significant hormonal side effects during treatment with atypical antipsychotic (Zuardi et al. 1995). The patient, a 19-year-old woman, was referred to the inpatient unit of the Clinical Hospital of Ribeirão Preto because of aggressiveness, self-injury, incoherent thoughts and auditory hallucinations. She received CBD Drops in progressively increasing dosage, up to 1500 mg/day (in two divided doses) within four weeks. CBD was then stopped and replaced by placebo for 4 days. After that, haloperidol administration was started. Dosage adjustment was based on clinical evaluation. Diazepam was also administered in periods of great agitation. The mean daily dose of diazepam decreased after the beginning of CBD treatment from 16.3 to 5.7 mg/day. Two psychiatrists and two nurse auxiliaries evaluated the patient and the interviews were videotaped. At the end of the study, the videotapes were analyzed blindly and in a random sequence by another psychiatrist. Symptoms decreased after CBD treatment and there was a trend for worsening of the symptoms after drug withdrawal. The improvement obtained with CBD was not increased by haloperidol. This improvement was seen in all items of the rating scale employed, including those more closely related to psychotic symptoms, making it improbable that an anxiolytic action was the sole responsible for the antipsychotic effect.
In an open pilot study at the University of Sao Paulo CBD was effective in the treatment of psychotic symptoms in patients with Parkinson‘s disease (Zuardi et al. 2008). Six consecutive patients (four men and two women) with the diagnosis of Parkinson‘s disease and who had psychosis for at least 3 months were selected for the study. All patients received CBD in flexible doses (starting with an oral dose of 150 mg/day) for 4 weeks, in addition to their usual therapy. The psychotic symptoms showed a significant decrease under CBD treatment. CBD did not worsen the motor function. No adverse effect was observed during the treatment. Authors concluded that „these preliminary data suggest that CBD may be effective, safe and well tolerated for the treatment of the psychosis in PD.“
CBD Significantly Reduced Psychopathological Symptoms
The first controlled clinical study of CBD in schizophrenia was connected at the University of Cologne with 42 patients suffering from acute schizophrenia. It demonstrated that CBD significantly reduced psychopathological symptoms when compared to the initial status (Leweke et al. 2012). Half of them received 800 mg of oral CBD daily for four weeks and the other half the standard medicinal drug amisulpride, a potent antipsychotic, in a double-blind manner. Either treatment was safe and led to significant clinical improvement, but CBD presented with significantly less adverse effects. Moreover, cannabidiol treatment was accompanied by a significant increase in blood anandamide levels. “The results suggest that inhibition of anandamide deactivation may contribute to the antipsychotic effects of cannabidiol potentially representing a completely new mechanism in the treatment of schizophrenia,” authors wrote.