Cognition in Medical Cannabis Patients


Kelly Sagar and her research team of Harvard Medical School, USA, examined the long-term impact of medical cannabis on cognition.


Only patients older than 21 and certified for the treatment with medical cannabis were included in this study. Exclusion criteria were a history of medical cannabis treatment or frequent recreational use of cannabis (more than 15 lifetime uses). The patients completed baseline cognitive and clinical assessments prior to initiation of medical cannabis treatment in order to evaluate cognitive abilities without possible impacts of cannabis. The neurocognitive tests were designed to assess executive functions (e.g., attention, verbal learning, decision making) and memory as previous studies found poorer cognitive performance in recreational cannabis users. After starting treatment with medical cannabis, the patients returned for three follow-up assessments: after 3, 6, and 12 months. To limit practice effects, the researchers used alternate test forms at each follow-up. Further, various aspects of clinical state such as mood, sleep, and anxiety were examined at each follow-up to evaluate the efficacy of medical cannabis.

54 patients completed baseline assessments and returned for at least one follow-up visit after three months; 44 returned for two follow-ups after three and six months, and 32 patients completed all three follow-up appointments. Patients used medical cannabis to treat a variety of symptoms and conditions, including pain, anxiety or post-traumatic-stress-disorder, mood, and attention. They reported using medical cannabis on average 9 to 11 times per week either orally, via an oromucosal spray or inhalation. The analysis of the cannabinoid content revealed that on average CBD exposure (mg/week) was higher than THC exposure (mg/week).

Sagar and colleagues found improvements on measures of executive function in patients treated with medical cannabis. Verbal learning and memory performance remained stable throughout all visits. Moreover, patients reported improvements in mood and sleep quality as well as reductions in anxiety over the course of this study, indicating the efficacy of medical cannabis. However, there was no significant correlation between medical cannabis use and cognitive variables for either CBD or THC. Correlation analyses found greater improvements in mood and anxiety with a higher amount of CBD on average per week. A long-term improvement of these symptoms could therefore be related to the positive impact of medical cannabis on cognition.

This long-term study reveals that patients treated with medical cannabis may show enhanced rather than impaired executive functioning over time. This is in contrast to previous findings suggesting cognitive decrements among recreational users. Additionally, treatment with CBD is associated with greater improvements of clinical state relative to baseline.

Treatment with medical cannabis may improve cognitive performance by improving sleep quality, mood, and anxiety.



Referenz: Sagar, K. A., Dahlgren, M. K., Lambros, A. M., Smith, R. T., El-Abboud, C., & Gruber, S. A. (2021). 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(6), 648-660.