Around-the-clock oral THC effects on sleep in male chronic daily cannabis smokers.

BACKGROUND AND OBJECTIVES Δ9-tetrahydrocannabinol (THC) promotes sleep in animals; clinical use of THC is associated with somnolence. Human laboratory studies of oral THC have not shown consistent effects on sleep. We prospectively evaluated self-reported sleep parameters during controlled oral THC administration to research volunteers. METHODS Thirteen male chronic daily cannabis smokers (mean ± SD age 24.6± 3.7 years, self-reported smoking frequency of 5.5 ± 5.9 (range 1-24) joint-equivalents daily at study entry) were administered oral THC doses (20 mg) around-the-clock for 7 days (40-120 mg daily) starting the afternoon after admission. The St. Mary's Hospital Sleep Questionnaire was completed every morning. Plasma THC and 11-OH-THC (active metabolite) concentrations were measured in venous blood samples collected every evening. Changes in sleep characteristics over time and associations between sleep characteristics and plasma cannabinoid concentrations were evaluated with repeated measures mixed linear regression. RESULTS Higher evening THC and 11-OH-THC concentrations were significantly associated with shorter sleep latency, less difficulty falling asleep, and more daytime sleep the following day. In contrast, the duration of calculated and self-reported nighttime sleep decreased slightly (3.54 and 5.34 minutes per night, respectively) but significantly during the study. CONCLUSIONS These findings suggest that tolerance to the somnolent effects of THC may have occurred, but results should be considered preliminary due to design limitations. SCIENTIFIC SIGNIFICANCE Somnolence from oral THC may dissipate with chronic, high-dose use. This has implications for patients who may take chronic oral THC for medicinal purposes, including cannabis dependence treatment. (Am J Addict 2013;22:510-514).