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Original Investigation
June 10, 2020

Association of Naturalistic Administration of Cannabis Flower and Concentrates With Intoxication and Impairment

Author Affiliations
  • 1Department of Psychology and Neuroscience, University of Colorado, Boulder
  • 2Division of Substance Dependence, Department of Psychiatry, University of Colorado, Aurora
  • 3Institute for Cognitive Science, University of Colorado, Boulder
  • 4Department of Health and Exercise Science, Colorado State University, Fort Collins
  • 5Department of Anesthesiology, University of Colorado, Aurora
JAMA Psychiatry. 2020;77(8):787-796. doi:10.1001/jamapsychiatry.2020.0927
Key Points

Question  What is the association of legal market cannabis flower and concentrates with cannabis intoxication and neurobehavioral impairment?

Findings  In this cohort study of 121 cannabis flower users and concentrate users randomly assigned to higher- vs lower-THC products within user groups, use of legal market cannabis concentrates (ranging from 70%-90% tetrahydrocannabinol [THC]) produced significantly higher THC blood plasma levels compared with use of legal market cannabis flower (ranging from 16%-24% THC). Despite differences in THC exposure, flower and concentrate users showed similar neurobehavioral patterns after acute cannabis use and the domains of verbal memory and proprioception-focused postural stability for both groups were associated with THC.

Meaning  Use of cannabis concentrates was associated with higher THC exposure and potentially greater risk, but differences in short-term subjective and neurobehavioral impairments did not track specifically with strength of the cannabis consumed.


Importance  The rapidly growing legal cannabis market includes new and highly potent products, the effects of which, to our knowledge, have not previously been examined in biobehavioral research studies because of federal restrictions on cannabis research.

Objective  To use federally compatible, observational methods to study high-∆9-tetrahydrocannabinol (THC) legal market forms of cannabis.

Design, Setting, and Participants  In this cohort study with a between-groups design that was conducted in a community and university setting, cannabis flower users and concentrate users were randomly assigned to higher- vs lower-THC products within user groups. Participants completed a baseline and an experimental mobile laboratory assessment that included 3 points: before, immediately after, and 1 hour after ad libitum legal market flower and concentrate use. Of the 133 individuals enrolled and assessed, 55 regular flower cannabis users (41.4%) and 66 regular concentrate cannabis users (49.6%) complied with the study’s cannabis use instructions and had complete data across primary outcomes.

Exposures  Flower users were randomly assigned to use either 16% or 24% THC flower and concentrate users were randomly assigned to use either 70% or 90% THC concentrate that they purchased from a dispensary.

Main Outcomes and Measures  Primary outcome measures included plasma cannabinoids, subjective drug intoxication, and neurobehavioral tasks testing attention, memory, inhibitory control, and balance.

Results  A total of 121 participants completed the study for analysis: 55 flower users (mean [SD] age, 28.8 [8.1] years; 25 women [46%]) and 66 concentrate users (mean [SD] age, 28.3 [10.4] years; 30 women [45%]). Concentrate users compared with flower users exhibited higher plasma THC levels and 11-hydroxyΔ9-THC (THC’s active metabolite) across all points. After ad libitum cannabis administration, mean plasma THC levels were 0.32 (SE = 0.43) μg/mL in concentrate users (to convert to millimoles per liter, multiply by 3.18) and 0.14 (SE = 0.16) μg/mL in flower users. Most neurobehavioral measures were not altered by short-term cannabis consumption. However, delayed verbal memory (F1,203 = 32.31; P < .001) and balance function (F1,203 = 18.88; P < .001) were impaired after use. Differing outcomes for the type of product (flower vs concentrate) or potency within products were not observed.

Conclusions and Relevance  This study provides information about the association of pharmacological and neurobehavioral outcomes with legal market cannabis. Short-term use of concentrates was associated with higher levels of THC exposure. Across forms of cannabis and potencies, users’ domains of verbal memory and proprioception-focused postural stability were primarily associated with THC administration.

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