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Acute Effects of Cannabis in Healthy Infrequent Users
Study Questions:
What are the comparative acute dose effects of smoked and vaporized cannabis using controlled administration methods?
Methods:
A within-participant, double-blind crossover study was conducted from June 2016 to January 2017 in 17 healthy adults. Six smoked and vaporized outpatient experimental sessions (1-week washout between sessions) were completed in clusters. Cannabis containing Δ9-tetrahydrocannabinol (THC) doses of 0 mg, 10 mg, and 25 mg were vaporized and smoked by each participant. Outcomes included change from baseline scores for vital signs and blood THC concentrations, subjective drug effects, and cognitive and psychomotor performance measured as computerized tasks representative of workplace performance and/or operation of a motor vehicle.
Results:
Subjects were 27.3 [5.7] years; nine men and eight women with no cannabis use in the prior month. Mean days since last cannabis use were 398 [437] days). Inhalation of cannabis containing 10 mg of THC produced discriminative drug effects (mean ratings [standard deviation] on a 100-point visual analog scale, smoked: 46 [26]; vaporized: 69 [26]) and modest impairment of cognitive functioning. The 25 mg dose produced significant drug effects ratings (smoked: 66 [29]; vaporized: 78 [24]), increased incidence of adverse effects, and pronounced impairment of cognitive and psychomotor ability (e.g., significant decreased task performance compared with placebo in vaporized conditions). Vaporized cannabis resulted in qualitatively stronger drug effects for most pharmacodynamic outcomes and higher peak concentrations of THC in blood, compared with equal doses of smoked cannabis (25 mg dose: smoked, 10.2 ng/ml; vaporized, 14.4 ng/ml). Blood THC concentrations and heart rate peaked within 30 minutes after cannabis administration and returned to baseline within 3-4 hours. Several subjective drug effects and observed cognitive and psychomotor impairments persisted for up to 6 hours on average.
Conclusions:
Vaporized and smoked cannabis produced dose-orderly drug effects, which were stronger when vaporized. These data can inform regulatory and clinical decisions surrounding the use of cannabis among adults with little or no prior cannabis exposure.
Perspective:
While medical marijuana has been shown to be very helpful, the adverse effects of long-term use and acute effects on judgment, concentration, and motor skills for driving, for example, are not known. How much and how used are just beginning to be evaluated by important scientifically rigorous studies, which in this case was a small cohort of young adults. Importantly, what is the impact of cannabis on psychomotor skills and judgment based on age, hypertension, chronic kidney disease, impaired liver function, drug interactions, and relatively mild subclinical cognitive impairment?
Clinical Topics: Prevention, Smoking
Keywords: Cannabinoids, Cannabis, Cognition, Dronabinol, Drug Interactions, Marijuana Smoking, Medical Marijuana, Motor Skills, Motor Vehicles, Primary Prevention, Psychomotor Disorders, Psychomotor Performance, Smoke, Task Performance and Analysis, Visual Analog Scale
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