This study will be a within-subject, random order, double-blind cross-over study with standard clinical and neuropsychological ratings. Duration is 13 weeks per subject. Clinical assessments including mood ratings will be performed weekly. Instructions and practice on the use of the spray will be given under supervision during a 2-week run-in period before baseline. Patients can control the dosage of cannabinoids according to their symptoms by administering up to a maximum of 48 pump-controlled sprays per day. Patients will be asked to abstain from using cannabis (other than the study drug) during the study. Patients will be treated for 4 weeks with either the sublingual THC:CBD spray or placebo spray. This will be followed by a 2-week washout period before another 4 weeks of treatment with whichever study medication was not initially used. Neurocognitive testing will be performed 3 times during the study. A mood diary will be completed daily by each patient at home.