A new study released by the National Institutes of Health (NIH) of 622 young Australian adults and 474 middle-aged men from the United States found that “normal variation in cannabis use is statistically unrelated to individual differences in brain morphology as measured by subcortical volume.” The study adds to the growing evidence (now over 69 studies) that marijuana use does not adversely impact cognitive performance.
This newest study using magnetic resonance imaging (MRI) and volumetric segmentation methods found that cannabis use did not affect the subcortical ROIs. An interesting result of the study did find a relationship with high nicotine use was associated with significantly smaller thalamus volumes in the middle-aged men.
Another study released last month in JAMA found similar conclusions relating to young adults and adolescents. Associations between cannabis use and cognitive functioning in cross-sectional studies of adolescents and young adults are small and may be of questionable clinical importance for most individuals. Furthermore, abstinence of longer than 72 hours diminishes cognitive deficits associated with cannabis use. Although other outcomes (eg, psychosis) were not examined in the included studies, results indicate that previous studies of cannabis in youth may have overstated the magnitude and persistence of cognitive deficits associated with use. Reported deficits may reflect residual effects from acute use or withdrawal. Future studies should examine individual differences in susceptibility to cannabis-associated cognitive dysfunction.
So, regardless of the Reefer Madness of the past and current myths surrounding marijuana and the brain, fear not, for science moves forward dispelling unsubstantiated claims.