LONDON, UNITED KINGDOM — Regular users of cannabis demonstrate limited, or in some cases, no impairment on measurements of either cognitive or psychomotor performance, according to data published in the journal Neuroscience and Biobehavioral Reviews.
British researchers conducted a systematic review of all human trials examining whether subjects exhibit tolerance to the effects of cannabis following repeated dosing. Thirty-six trials, involving over 1000 subjects, were included in their review.
Authors reported that repeated exposure to either cannabis or THC was associated with partial or full tolerance in subjects, particularly with regard to cognitive performance and psychomotor abilities.
They reported: “Studies indicated relatively minor or no effects of repeated Δ9-THC administration in RU (regular users) on a number of cognitive domains including learning, memory, vigilance, and psychomotor ability. This absence of effect in RU might indicate the development of full tolerance.”
Investigators concluded: “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. The acute intoxicating and cardiac effects of Δ9-THC are also blunted upon regular exposure. Similar but limited evidence also suggests blunted acute psychotomimetic effects of Δ9-THC in individuals using cannabis regularly.”
Full text of the study, “Cannabis use and the development of tolerance: A systematic review of human evidence,” appears in Neuroscience and Biobehavioral Reviews.