Obsessive-compulsive disorder (OCD) is a severe and underdiagnosed mental disorder that causes substantial impairments in most patients’ quality of life. It is characterized by the presence of obsessions - which are recurrent and persistent thoughts, urges, or images that are intrusive, unwanted, and cause anxiety and distress - and compulsions - which are repetitive behaviors or mental acts that the patient performs to alleviate the obsessions.
The endocannabinoid system (ECS) is a prevalent and important signaling system in the brain, which comprises native signalling molecules called endocannabinoids, cannabinoid receptors CB1 and CB2 which they (as well as plant-based cannabinoids like THC) bind to, and the enzymes that synthesize and degrade them. In the early 2000s, data obtained from several animal studies suggested the involvement of the brain’s ECS in causing OCD, as well as the improvement of OCD-like behaviors following stimulation of the ECS.
Based on these findings, psychologists and psychotherapists began a careful, deliberate experimentation on treating OCD with drugs that stimulate the ECS. Starting 2008, case reports and trials on the benefits of cannabinoid-derivative medicines in patients with pure OCD began being conducted. Since then, successful treatment with dronabinol - the synthetic form of THC from cannabis - which activates brain cannabinoid receptors CB1, in patients with treatment refractory OCD has been documented twice. In addition, data from a small uncontrolled trial using the THC analogue nabilone suggested that the combination of nabilone and exposure-based psychotherapy is more effective than each treatment alone for improving OCD. Most recently, an international group of psychologists and psychotherapists from Poland and Germany presented the case of a young male patient, who suffered from severe OCD since childhood and developed associated depression during adolescence. This patient’s severe symptoms significantly improved after treatment with the cannabis-based drug Bedrocan (containing 22% THC and <1% CBD) with markedly reduced OCD and depression, which considerably improves his quality of life.
Through these case reports and uncontrolled trials, the researchers highlighted the great potentials of cannabis-based medicine in treating OCD. Nonetheless, more in-depth studies into the mechanisms of actions of these drugs, as well as more controlled trials with bigger participant pools are required before cannabis-based medicine can be officially recognized and established as a standard treatment for OCD.