The discovery of endocannabinoid’s role within the central nervous system and its potential therapeutic benefits have brought forth rising interest in the use of cannabis for medical purposes. The present review aimed to synthesize and evaluate the available evidence on the efficacy of cannabis and its derivatives for psychiatric, neurodegenerative and movement disorders.
A systematic search of randomized controlled trials of cannabis and its derivatives were conducted via databases. A total of 24 reports that evaluated the use of medical cannabis for Alzheimer’s disease, anorexia nervosa, anxiety, dementia, dystonia, Huntington’s disease, Parkinson’s disease, post-traumatic stress disorder (PTSD), psychosis and Tourette syndrome were included in this review.
Cannabis has long been used for medical and recreational purposes. The Cannabis sativa and Cannabis indica are two common species used for consumption.
- Between the two species, C. sativa has comparatively higher delta-9-tetrahydrocannabinol (THC) concentration while C. indica has comparatively higher cannabidiol concentration.
- Cannabinoids can be classified into three subtypes, endocannabinoids (naturally present in human body), phyto-cannabinoids (present in cannabis plant) and synthetic cannabinoids (produced chemically).
- Presently, over 60 different types of pharmacologically active cannabinoids have been identified and isolated from the cannabis plant. These include the exogenous cannabinoids such as the psychoactive THC and non-psychoactive cannabidiol, as well as the endogenous cannabinoids such as anandamide, which affects most systems in the human body, especially the central nervous system.
Medical Cannabis & Psychiatric Disorders
- In a trial involving 11 females with anorexia nervosa, titrated THC 7.5 mg (2.5 mg, three times a day) to a maximum of 30 mg (10 mg, three times a day) showed similar weight gain to titrated diazepam 3.0 mg (1 mg, three times a day) to 15.0 mg (5 mg, three times a day).
- The anti-anxiety efficacy of cannabinoids was assessed in 5 studies involving a total of 38 patients and 44 healthy volunteers. Within this study, 1 mg Nabilone administered twice daily for 28 days significantly improved anxiety measured by the Hamilton Rating Scale for Anxiety.
- More recently, in a parallel study, 24 generalized social anxiety disorder patients were randomized to receive either a single dose of 600 mg cannabidiol or placebo and were also subjected to a simulated public speaking test. Pre-treatment of cannabidiol significantly reduced anxiety measured by the visual analogue mood scale.
- In another crossover trial involving 10 male patients with generalized social anxiety disorder, a single dose of 400 mg cannabidiol was associated with a significant decrease in subjective anxiety measured by the visual analogue mood scale.
Post-Traumatic Stress Disorder
- In a first randomized controlled crossover trial on PTSD, 10 males with PTSD associated nightmares were administered with titrated 0.5 to 3.0 mg nabilone or placebo, in two 7-week treatment periods, separated by a 2-week washout period.
To date, only one published trial investigated the antipsychotic properties of cannabidiol in patients with schizophrenia.
- In a 4-week parallel, active-controlled trial, 42 patients with schizophrenia were randomized to receive either cannabidiol or amisulpride. Significant clinical improvements were observed in both treatments as indexed by the Brief Psychiatric Rating Scale and the Positive and Negative Syndrome Scale.
Medical Cannabis & Neurodegenerative Disorders
- One trial on Alzheimer’s disease examined the use of dronabinol for managing Alzheimer’s disease. In a 6-week crossover trial, 2.5 mg dronabinol appeared to reduce disturbed behaviors in 12 patients, as measured by the Cohen-Mansfield Agitation Inventory.
- In a 4-week trial, 2.5 mg dronabinol reduced night-time agitation and strengthened circadian rhythms in the 2-patient enrolled in the study.
Medical Cannabis & Movement Disorders
- In a 10-week placebo-controlled crossover trial, nabilone (1 or 2 mg) showed significant treatment effect as measured by the total motor and chorea score on the Unified Huntington’s Disease Rating Scale (UHDRS).
- In an early crossover trial involving 9 Parkinson’s disease patients with dyskinesia, 0.03 mg/kg nabilone significantly improved dyskinesia as indexed by the Rush dyskinesia disability scale.
- More recently, in a placebo-controlled trial, 21 patients with Parkinson’s disease were randomized to receive cannabidiol (75 mg/day or 300 mg/day) or placebo for 6 weeks. A significant improvement was reported for PDQ-39, particularly the activities of daily living and stigma subscale for the 300 mg/day cannabidiol group.
- In a placebo-controlled crossover trial, 12 patients with Tourette syndrome received a single dose of THC 5 to 10 mg (dose based on body weight). Using the Tourette Syndrome Symptom List, there was a significant treatment effect of THC on the subscale of tics and obsessive-compulsive behavior.
- In another 6-week trial from the same research group, 24 patients with Tourette syndrome were given oral THC up to 10 mg per day. Similarly, THC significantly reduced tics compared to placebo.
Conclusion & Future Implications
While there are trials that suggest potential benefit of cannabinoids for anorexia nervosa, anxiety, PTSD, psychotic symptoms agitation in Alzheimer’s disease and dementia, Huntington’s disease, and Tourette syndrome, and dyskinesia in Parkinson’s disease, further research is necessary to draw accurate conclusions pertaining to the efficacy of cannabinoids.
An improved knowledge of the precise mechanism of cannabinoids at the cellular level could provide insights on the therapeutic benefits of cannabinoids for movement, psychiatric and neurodegenerative disorder. This could facilitate development of cannabinoid formulations and the conducts of clinical trials on these indications.