Observational study of visual testing efficacy in detecting cannabis usage

Abstract

Drug recognition and examination programs are widely used to detect drug impairment in motor vehicle operators. Visual tests are a key assessment in the detection of cannabis-related impairment. Participants were recruited via social media from the medical cannabis community in Southwestern Ontario, Canada. Twenty-two participants completed the full observational trial design. The majority (n = 13 or 59.1%) were male, with a mean age of 36 years (SD = 9.4; range: 24–59). Participants underwent the following protocol: 1) First round of testing (vital signs, bio sample collection, visual tests, subjective data, neurocognitive testing) (Baseline phase); 2) Consumption of cannabis via inhalation; 3) Second round of testing 30 minutes following consumption (THC phase); 4) Additional rounds of testing at 90, 150, and 210 minutes following consumption (Recovery phase). Visual assessment data and vital signs did not follow typical patterns associated with acute cannabis intoxication. With blood THC levels more than double the Canadian legal limit (5 ng/mL), visual testing results were not diagnostic for cannabis impairment, as participants maintained normal pupil sizes and normal ocular convergence patterns. Visual testing is a key component in standardized examinations used for detecting cannabis-related impairment in Canadian drivers; however, our data indicate that visual testing may not be an effective diagnostic tool for the specific population of medical cannabis users.

Testing for cannabis intoxication: Current issues and latest advancements

“…It has been reported that visual testing is not diagnostic for cannabis impairment (Olla et al, 2021), and mixed sensitivities of FSTs in identifying cannabis intoxication via inhalation and oral exposure have been reported. Bosker, Theunissen, et al (2012) concluded that cannabis inhalation was related to the OLS test in heavy users, which was later supported by the work of Porath‐Waller and Beirness (2014), Hartman, Richman, et al (2016), Declues et al (2016), and Spindle et al (2021).…”