A Semi-Naturalistic, Open-Label Trial Examining the Effect of Prescribed Medical Cannabis on Neurocognitive Performance

Background and objectives

Medical cannabis use is increasing in Australia and other jurisdictions, yet little is known about the effects of medical cannabis on cognitive function. Findings from studies of non-medical (‘recreational’) cannabis may not be applicable to patients using prescribed medical cannabis to manage a health condition.

Methods

In this semi-naturalistic, open-label trial, patients with various health conditions attended a single laboratory session in which they self-administered a standard dose of prescribed medical cannabis as per instructions on the pharmacy label. We assessed cognitive performance using the Cambridge Neuropsychological Test Automated Battery (CANTAB) and Druid application (app) prior to and following (CANTAB: + 3 h; Druid: + 3 and 5.5 h) medical cannabis self-administration. We also assessed subjective drug effects prior to and following (1, 2 and 4 h) medical cannabis self-administration using a range of 0–10 cm visual analogue scales (‘stoned’, ‘sedated’, ‘relaxed’, ‘comfortable’, ‘anxious’ and ‘confident’). Data were analyzed using linear fixed-effect models.

Results

Participants (N = 40; 22 females) were prescribed a range of products including orally administered oils (n = 23) and flower for vaporization (n = 17). Participants had a mean (standard deviation [SD]) age of 41.38 (12.66) years and had been using medical cannabis for a mean (SD) of 10.18 (8.73) months. Chronic non-cancer pain was the most common indication for medical cannabis use (n = 20), followed by sleep disorder (n = 18) and anxiety (n = 11). The mean (SD) delta-9-tetrahydrocannabinol (THC)/cannabidiol (CBD) dose administered by participants was 9.61 (8.52) mg/9.15 (10.11) mg among those using an oil, and 37.00 (24.53) mg/0.38 (1.58) mg among those who vaporized flower, respectively. Participants’ performance improved over time on the CANTAB Multitasking Test and Rapid Visual Information Processing test (both p-values <0.001). All other changes in cognitive performance measures over time were non-significant (p > 0.05). Vaporization of flower was associated with significantly stronger subjective feelings of ‘stoned’ and ‘sedated’ relative to oils (both p < 0.001).

Conclusions

These findings suggest that prescribed medical cannabis may have minimal acute impact on cognitive function among patients with chronic health conditions, although larger and controlled trials are needed.