Legal-Market Cannabis Tied To Short-Term Neurobehavioral Impairments

Legal-market cannabis flower and concentrate use was linked to delayed recall memory and balance impairment in an observational study.

"Recent reviews have suggested that today's higher potency cannabis may lead to more intoxication and impairment," Dr. L. Cinnamon Bidwell of the University of Colorado Boulder told Reuters Health by email. "But prior to this study, we had no empirical data to determine the real risk profile of these high-tetrahydrocannabinol (THC) products."

"In this study, we focused on real-world users of high-potency, legal-market forms of cannabis," she said. "Our findings suggest vast differences in THC potency and exposure across flower and concentrate users."

Dr. Bidwell and colleagues randomly assigned cannabis flower and concentrate users to higher-versus lower-THC products within the two user groups. Participants completed mobile laboratory assessments before, immediately after, and one hour after ad libitum legal-market flower and concentrate use.

Flower users were randomly assigned to either 16% or 24% THC flowers; concentrate users were randomly assigned to either 70% or 90% THC concentrate, purchased from a dispensary.

As reported in JAMA Psychiatry, of the 133 individuals enrolled and assessed, 55 regular flower cannabis users (41.4%) and 66 regular concentrate cannabis users (49.6%) had complete data across the primary outcomes.

Participants' mean age was about 28 and about 45% were women. Per the study criteria, all had used cannabis at least four times in the previous month; had no adverse reaction to the highest cannabis potency assigned; did not use any other non-prescription drugs within the previous 60 days; did not use tobacco; drank two times or less per week and had three drinks or fewer per occasion; were not pregnant; and were not being treated for a psychotic or bipolar disorder.

Concentrate users compared with flower users had higher plasma THC levels and 11-hydroxy-THC (THC's active metabolite) across all points. After ad libitum cannabis use, mean plasma THC levels were 1,016 mcg/mL in concentrate users and 455 mcg/mL in flower users.

Most neurobehavioral measures were not affected by short-term cannabis consumption. However, delayed verbal memory and balance function were impaired after use. No differences were seen in the type of product used (flower vs. concentrate) or potency within products. Concentrate users demonstrated similar or lower levels of subjective drug intoxication and short-term impairment compared with users of lower-potency flowers.

Dr. Bidwell said, "Clinicians should educate themselves about the different forms of cannabis their patients use and at what frequency. Different and more varied forms of administration are available on legal markets and the more clinicians can learn, the better. This helps in being prepared for frank and detailed conversations about harms and potential benefits of their use."

"These high-potency concentrates are associated with very high THC exposure, so in patients with other risk factors, that may be a concern," she noted. "Encouraging discussion between patients and providers around use and potency is an important path forward in allowing people to make informed choices."

Dr. Timothy Brennan, Director of the Addiction Institute at Mount Sinai West and Mount Sinai St. Luke's in New York City, commented in an email to Reuters Health, "There are a great many unknowns about cannabis because it is particularly cumbersome to study because of federal restrictions. What is known is that the cannabis that is for sale today is dramatically more potent than the cannabis that was for sale in the late 1960s and early 1970s."

"There is very little quality control in the legal cannabis industry regarding concentration, so customers should be aware that a product at one shop may be dramatically stronger than a similar product at a different shop," he noted.

"Cannabis is an intoxicant," he said, "so it is not surprising that users experienced delayed verbal memory and impaired balance function."

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Marijuana should be legal in every state.