Does Cannabidiol Attenuate the Acute Effects of ∆9-tetrahydrocannabinol Intoxication in Individuals Diagnosed With Schizophrenia? A Double-blind, Randomised, Placebo-controlled Experimental Study

Inclusion criteria: * Age 18-65 years. * Clinical diagnosis of schizophrenia (i.e. documented as such in the patient's clinical records and satisfying ICD-10 criteria for F20) * Clinically stable for at least three months (since discharge from hospital, home treatment team, or prior clinical deterioration, and with agreement from the patient's responsible clinician) * Regular (at least weekly) cannabis use for the past 3 months or more * Evidence from either clinicians or from the patient that cannabis use exacerbates their symptoms or increases their risk of relapse * Treatment with regular doses of antipsychotic medication for at least 1 month, confirmed by a blood test at the baseline visit, and with the participant agreeing to be maintained at a stable dose over the course of the experiment * The participant agrees to abstain from cannabis use for at least 24hours prior to study visits * The participant is willing to have an intravenous cannula inserted to collect blood samples on experimental visits * Sufficiently fluent English * Providing written informed consent Exclusion criteria: * Extreme cannabis use: participant is estimate to be using over 1gram of cannabis/day * Dependence on alcohol or illicit substances other than cannabis as defined by ICD-10 * Pregnancy (current or planned) or breastfeeding * Physical health disorder or another mental health disorder that the study psychiatrist judges may influence the patient's ability to tolerate the procedure, or that…