Impact of Cannabis Smoking on Multiple Sleep Latency Test Outcomes

Our purpose was to evaluate how cannabis smoking influenced multiple sleep latency test (MSLT) outcomes. This was a retrospective study of all adults that had undergone a MSLT at St. Michael's Hospital (Toronto, Ontario, Canada) from 1 January 2008 until 31 December 2018. Three groups of persons were considered: active cannabis-only smokers, active tobacco-only smokers and non-active cannabis and tobacco smokers. A range of outcomes from the MSLT and preceding overnight polysomnogram were evaluated. Descriptive statistics at the univariate level were used. We identified a total of 139 individuals undergoing MSLT, of whom 9 (6.5%) were active cannabis-only smokers, 14 (10.0%) were active tobacco-only smokers and 116 (83.4%) were non-smokers. There were non-significant trends among cannabis-only smokers versus non-smokers and tobacco-only smokers towards lower mean sleep onset latency on MSLT (8.1 min vs. 9.2 min and 10.5 min, respectively) and there was a greater proportion of severe sleepiness (33.3% vs. 22.4% and 14.3%, respectively), having at least one REM sleep onset period (55.6% vs. 28.4% and 42.9%, respectively), narcolepsy diagnosis (22.2% vs. 8.6% and 7.1%, respectively), and idiopathic hypersomnia diagnosis (33.3% vs. 30.2% and 14.3%). Although we found no significant differences among the groups we evaluated, there were non-significant trends in multiple outcomes indicative of hypersomnia among active cannabis-only smokers, most notable of which were more frequent (and potentially incorrect) diagnoses of narcolepsy and idiopathic hypersomnia.