Even though cognitive impairments are generally reported by studies examining recreational cannabis users, particularly in those in adolescence, few studies have assessed the impact of medical cannabis use on cognition. The results may be different for medical cannabis users with different motives for use, age of onset, production selection, and administration methods, dose, frequency, and duration.
One recent observational study assessed the cognitive functions in 54 medical cannabis patients by visiting them four times over one year: a baseline visit before the medical treatment, and visits after 3,6, and 12 months of the treatment. At each visit, patients completed two evaluations: one neurocognitive test assessing executive function, verbal learning/memory, and one clinical state measurement assessing mood, anxiety, and sleep.
The study found that, relative to baseline, medical cannabis patients had significant improvements on executive function and clinical state; verbal learning/memory performance generally remained stable. Improved cognitive performance was not correlated with medical use (episodes/week, THC mg/week, or CBD mg/week), but analyses suggest cognitive improvements were associated with improved medical condition. Clinical improvement in mood and anxiety was associated with higher CBD use. The study concluded that medical cannabis patients may exhibit enhanced rather than impaired executive function over time. Future studies should examine distinctions between recreational and medical cannabis use to identify potential mechanisms related to cognitive changes.
1. Sagar, K. A. et al. An Observational, Longitudinal Study of Cognition in Medical Cannabis Patients over the Course of 12 Months of Treatment: Preliminary Results. Journal of the International Neuropsychological Society 27, 648–660 (2021).