Abstract
RATIONALE: Cannabidiol (CBD) is increasingly used as a sleep aid for insomnia; yet neurocognitive and subjective state effects following daily therapeutic use are unclear. OBJECTIVES: To measure the effect of daily CBD use on neurocognitive performance and daily subjective mood in a population with primary insomnia. METHODS: This study used a randomized, placebo-controlled, parallel design incorporating a single-blind placebo run-in week followed by a two-week double-blind dosing period, during which participants consumed 150 mg CBD (N = 15) or placebo (N = 15) sublingually 60-minutes daily before bed. Attention, executive function, reasoning, information processing, working and episodic memory were assessed using the CogPro system at the beginning of the placebo run-in, after 1-week and 2-weeks of dosing. Subjective states using visual analogue scales and side effects were recorded daily. RESULTS: Cognitive performance was unaffected by nightly CBD supplementation (all p > 0.05). From baseline to trial conclusion, those receiving CBD reported greater experience of calmness, clear-headedness, coordination and were more likely to report side-effects of dry mouth relative to placebo (all p < 0.05). CONCLUSIONS: Relative to placebo, daytime cognitive functioning following nightly supplementation as a therapeutic aid for primary insomnia was preserved under trial conditions. Results suggested an overall favourable safety profile, with larger controlled trials and thorough analyses of varying insomnia phenotypes necessary to corroborate these findings.