ABSTRACT
Objective: This review summarises the existing evidence on the effects that recreational and medical use of cannabis and cannabinoids have on cognitive performance. Methods: Databases (PubMed, Medline, and Google Scholar) were searched from inception to March 2017 by adopting the following key terms: dronabinol, nabilone, nabiximols, cannabis, marijuana, cognition, neurology, and neuropsychology. A total of 94 documents, including reviews, preclinical and clinical studies, industrial and government agencies reports were included in this review. Results: We found that recreational use of cannabis doubles the risk of a fatal traffic accident by impairing attention and lengthening reaction time. Short-term use lowers performance in working memory, attention, executive functions and visual perception tasks. Chronic recreational use in adolescents also doubles the risk of early school-leaving, cognitive impairment and psychoses in adulthood. Adverse effects of cannabis-based medication – dronabinol, nabiximol and nabilone – and ingestion/inhalation of marijuana allowed for medical use include dizziness, drowsiness and short-term memory impairment. Conclusion: Cannabis consumption is associated with significant impairments in a range of cognitive abilities. Of particular concern, early and chronic exposure to cannabis, especially in the adolescence, seems to be associated with irreversible cognitive impairments.
ABSTRACT
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 evidences 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 (PubMed, Embase and the Cochrane Central Register of Controlled Trials). 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. Trial quality was assessed with the Cochrane risk of bias tool. There is a lack of evidence on the therapeutic effects of cannabinoids for amyotrophic lateral sclerosis and dystonia. Although trials with positive findings were identified 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, definitive conclusion on its efficacy could not be drawn. Evaluation of these low-quality trials, as rated on the Cochrane risk of bias tools, was challenged by methodological issues such as inadequate description of allocation concealment, blinding and underpowered sample size. More adequately powered controlled trials that examine the long and short term efficacy, safety and tolerability of cannabis for medical use, and the mechanisms underpinning the therapeutic potential are warranted.