Cannabinoid Medication for Adults With OCD

The purpose of this pilot research study is to test the effects of a medication called nabilone (Cesamet) in adults with obsessive-compulsive disorder (OCD). Participants will receive either nabilone on its own, or nabilone in combination with a form of cognitive-behavioral therapy (CBT) called exposure and response prevention (EX/RP). Nabilone is a synthetic cannabinoid and acts on the brain's "endocannabinoid system," which has been hypothesized to play a role in OCD. Nabilone is approved by the FDA for the treatment of chemotherapy-induced nausea and vomiting. It is not FDA-approved for treating OCD.

The two first-line treatments for OCD are a class of medications called serotonin reuptake inhibitors (SRIs) and a type of cognitive behavioral therapy called exposure and response prevention (EX/RP). But more than a third of patients with OCD do not respond to these treatments, and less then half become well. Thus, new treatment approaches are needed. EX/RP is thought to involve fear extinction learning. Recent research suggests that modulators of the endocannabinoid system such as nabilone (a synthetic cannabinoid and agonist of the cannabinoid 1 receptor, CB1R) may enhance fear extinction learning and therefor could enhance EX/RP. However, nabilone could also work via modulating activity in cortico-striatal circuits, which contain high concentrations of CB1R, and thereby might reduce repetitive behaviors like compulsions seen in OCD. To test both ideas, we will conduct a small pilot randomized trial to explore the effects of nabilone on its own for 4 weeks, vs. combined with EX/RP, in adult patients with OCD. This proof-of-concept study will investigate whether nabilone administration is feasible and well-tolerated in adult patients with OCD. The intent is to collect pilot data to support future grant applications.

Will receive nabilone at 1 mg daily (BID) plus therapist-guided Exposure and Response Prevention Therapy during 4 weeks.

Nabilone is a synthetic cannabinoid that is thought to be a Cannabinoid receptor type 1 (CB 1) agonist. It acts on the brain's "endocannabinoid system," which has been hypothesized to play a role in OCD.

Exposure and Response Prevention Therapy (EX/RP) is a type of Cognitive-Behavioral Therapy for OCD that involves intentionally confronting situations that trigger obsessional distress while refraining from doing compulsions.

Yale-Brown Obsessive Compulsive Scale (YBOCS) Minimum Value: 0 Maximum Value: 40 Higher scores indicate more severe symptoms Change in YBOCS is calculated by subtracting the Week 4 score from the baseline score

Inclusion Criteria: Age 18-60 Physically healthy, not pregnant Primary Obsessive-Compulsive Disorder (OCD) Patient off all psychotropic (except selective serotonin reuptake inhibitors [SSRIs]) and other types of drugs likely to interact with nabilone Ability to provide informed consent Ability to tolerate a treatment free-period Exclusion Criteria: History of any significant medical condition that may increase the risk of participation Females who are pregnant or nursing Current or lifetime history of psychiatric disorders other than OCD that may increase the risk of participation (e.g. lifetime psychosis or bipolar disorder) Current substance use disorder or positive urine toxicology at screening, or any adverse reaction to a cannabinoid Patients already receiving EX/RP