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Patients Do Not Exhibit Neurocognitive Performance Changes After Cannabis Use

human brain

Cannabis opponents have long touted the unfounded claim that ‘cannabis is bad for the human brain.’ Those claims always fail to provide proper context to the subject, which does a huge disservice to such a very important conversation.

To be sure, cannabis can have an effect on the human brain, but to what level and in which ways depends on several factors. That is why one patient can consume cannabis in the same manner as a second patient, the same dosage, and all things being equal, yet have a different experience.

Not all cannabis use results in a change in how the brain functions. Neurocognitive performance after cannabis use was at the heart of a recent study in Australia, and the results are insightful. Below is more information about it via a news release from NORML:

Melbourne, Australia: The use of medical cannabis is not associated with significant changes in patients’ cognitive performance or driving abilities, according to data published in the journal CNS Drugs.

Australian researchers assessed neurocognitive performance in a cohort of 40 patients authorized to use medical cannabis products. (Under Australian law, physicians may authorize cannabis products to patients unresponsive to conventional prescription treatments.) Participants’ performance was assessed at baseline and again three hours later. Patients either vaporized herbal cannabis or consumed oral extracts. Study participants had regularly used medical cannabis products for at least ten months prior to enrolling in the trial.

Patients exhibited no changes in simulated psychomotor performance, executive function, memory, or reaction time following their self-administration of a “standard dose of their prescribed medical cannabis.” Results were consistent regardless of the type of cannabis product consumed.

Investigators reported: “We found no evidence for impaired cognitive function when comparing baseline with post-treatment scores on a comprehensive neuropsychological test battery, nor did we observe any change in performance on the DRUID [psychomotor] test battery over time. … These findings are consistent with two systematic reviews published in the last year that suggest that medical cannabis, when used regularly and consistently for a chronic health condition, may have little if any impact on cognitive function.”

The study’s authors concluded, “Medical cannabis may have minimal acute impact on cognitive function when prescribed and used as directed.”

Other studies have similarly determined that habitual cannabis consumers become tolerant to cannabis-induced changes in either cognitive or psychomotor performance. According to a 2018 meta-analysis of 36 studies involving over 1,000 participants: “Available evidence suggests that the effects of acute marijuana or Δ9-THC administration are less prominent in individuals with a regular pattern of cannabis use compared to non-regular users. Cognitive function appears to be the domain most likely to demonstrate tolerance upon repeated exposure, with some evidence of full tolerance indicating a complete absence of acute effect.”

literature review published in the journal of the German Medical Association concluded, “Patients who take cannabinoids at a constant dosage over an extensive period of time often develop tolerance to the impairment of psychomotor performance, so that they can drive vehicles safely.”
Full text of the study, “A semi-naturalistic, open-label trial examining the effect of prescribed medical cannabis on neurocognitive performance,” appears in CNS Drugs. Additional information is available in the NORML Fact Sheet, ‘Marijuana and Psychomotor Performance.’