San Diego, CA: Smoking marijuana long-term has little-to-no impact on neurocognitive performance in adults, according to findings published last week in the Journal of the International Neuropsychological Society.
Researchers at the University of California, San Diego (UCSD) School of Medicine analyzed data from 15 previously published, controlled studies regarding the impact of long-term, recreational marijuana use on neurocognitive performance including simple reaction time, verbal/language skills, executive function, motor skills, learning, and recognition, among other measurements.
“The results of our meta-analytic study failed to reveal a substantial, systematic effect of long-term, regular cannabis consumption on the neurocognitive functioning of users who were not acutely intoxicated,” authors determined.
Marijuana smokers were indistinguishable from non-users in six of the eight neurocognitive ability areas surveyed, the study found. The two exceptions were in the domains of “learning” and “forgetting” (failure to recall or recognize), though authors said that marijuana’s apparent negative impact on these skills was so slight that “the ‘real life’ impact of such a small and selective effect is questionable.”
Because the studies did not measure volunteers’ neurocognitive abilities prior to their marijuana use, nor distinguish between marijuana-only smokers and polydrug users, authors said it was impossible to verify whether the small but measurable decrements to learning and forgetting were due to marijuana or other factors. Authors did note, however, that by failing to control for such factors, they “actually increased the likelihood of finding a [negative] cannabis effect.” As a result, they said it was “surprising to find [that marijuana has] such few and small effects” on neurocognitive abilities.
“The small magnitude of the effect[s] … suggests that cannabis compounds … should have a good margin of safety from a neurocognitive standpoint,” especially in controlled settings, authors concluded.
Allen St. Pierre, Executive Director of The NORML Foundation, said that the results reinforce NORML’s core position that marijuana prohibition causes far greater harm than the responsible use of marijuana itself. “The only significant long-term impact marijuana has upon cognitive function is upon those who continue to irrationally demonize and criminalize this plant,” he said.
For more information, please contact either Allen St. Pierre or Paul Armentano of the NORML Foundation, at (202) 483-8751.