Effects of Cannabidiol on Psychiatric Symptoms, Cognition, and Cannabis Consumption in Cannabis Users With Recent-Onset Psychosis

A large proportion of people with a schizophrenia-spectrum disorder, especially in the early stages of the disease, regularly consume cannabis. Cannabis use is associated with poor prognostic outcome; however, there are no effective interventions targeted at reducing cannabis use or its deleterious effects in this population. The present trial is designed to test whether cannabidiol (CBD), a cannabinoid whose effects are in many ways antagonistic to those of Δ9-tetrahydrocannabinol (THC), can reduce psychiatric symptoms, cognitive deficits, and cannabis use in people with recent-onset psychosis who regularly consume cannabis.

This is a double-blind, randomized, placebo-controlled trial, evaluating the effects of a 12-week treatment course with CBD on psychiatric symptoms, cognition, and cannabis consumption in regular cannabis users with recent-onset psychosis. The study will be conducted at the Maryland Psychiatric Research Center (University of Maryland School of Medicine) and associated Early Intervention Programs in Baltimore, at the Sheppard Pratt Health System in Baltimore, and at the Psychosis Clinic of the University of California Los Angeles.

The daily dose of CBD is 600 mg (p.o.), administered as adjunct medication. Any non-exclusionary antipsychotic, antidepressant, anxiolytic, or other medication prescribed prior to the trial will be continued. Participants may, but do not have to be taking conventional antipsychotic medication.

The study will include 84 regular cannabis users with a schizophrenia-spectrum disorder who experienced their first psychotic episode within the last 5 years (90). Participants will be randomized 1:1 to either the CBD or the placebo group.

Outcome measures include psychiatric symptoms, cognition, global functioning, and drug use, and will be assessed at baseline, and every 3 or 6 weeks thereafter (depending on the measure), until the end of treatment at 12 weeks. Outcome will be assessed again at a 3-month follow-up.

Eligibility Criteria:
Inclusion Criteria:

* DSM-5 diagnosis of schizophrenia, schizoaffective disorder, schizophreniform disorder, and other specified or unspecified schizophrenia spectrum and other psychotic disorder.
* Experienced a first psychotic episode within the last 5 years.
* Self-reported cannabis use at least twice/week for at least the last 4 weeks.
* THCCOOH serum levels of ≥ 5 ng/mL.
* Total score ≥45 on the 18-item version of the Brief Psychiatric Rating Scale.
* Able to give written informed consent.
* Normal or corrected to normal vision.
* If medicated, no change in psychiatric medication within the preceding 4 weeks, with no foreseeable changes.

Exclusion Criteria:

* DSM-5 diagnosis of Substance Use Disorder other that cannabis or nicotine within the last year (recreational use is not exclusionary).
* Currently undergoing active treatment for Cannabis Use Disorder other than low-level (once/week or less) psychosocial intervention.
* Uncontrolled hypertension (resting systolic BP above 150 or diastolic above 95 mm Hg).
* Cardiovascular disease, such as history of myocardial infarction and ischemia, heart failure, angina, severe arrhythmias, or EKG abnormalities (Wolf-Parkinson-White syndrome, Complete left bundle branch block, PR interval \<120 ms or \>200 ms, Prolonged QT interval (corrected) \>500 ms, Cardiac arrhythmias as defined by PACs \>3 per min or PVCs \>1 per min).
* History of or current neurological illness, such as stroke, seizure disorders, neurodegenerative diseases, or organic brain syndrome.
* Intellectual disability.
* Pregnant or lactating.
* Diabetes.
* Significant kidney or liver impairment.
* Any chronic or severe infectious disease, including HIV and hepatitis.
* Cancer.
* Use of any barbiturates, diazepam, diltiazem, verapamil, protease inhibitors, any anticonvulsant medications (including valproate/valproic acid, lamotrigine, carbamazepine, and clobazam), glipizide, glyburide, warfarin, and cyclophosphamide/ ifosfamide, due to potential interaction with CBD at the metabolic level.
* Suicidal ideation currently or within last 6 months (score of \>/= 3 on the Columbia Suicide Severity Rating Scale).
* Less than the lower limit of normal hemoglobin and hematocrit at screening.
* Elevated transaminase levels \>3 times the ULN, accompanied by elevations in bilirubin \>2 times the ULN.