For many years, cannabis (aka marijuana) was thought to cause brain damage, or kill brain cells. You've probably heard that sentiment echoed by the anti-pot lobby for decades now. And while the study from where this misinformation was largely derived was deeply mishandled, the stigma that marijuana was bad for the brain has tragically stuck. But that may soon change as a surprising new scientific study has revealed that there appears to be no harmful effects on the brain from marijuana use.
This new study was conducted with the collaboration of over 20 researchers representing over 13 institutions across the United States and Australia. It contradicts a 2015 study that showed the brain does change shape with marijuana use. In previous studies, the test groups were much smaller, and even some researchers were not sure if cannabis was what motivated the change in brain shape, or whether nutrition or stress played a factor.
This new study examined nearly 1100 patients. According to the report, "A total of 622 young Australian adults [66% female] and 474 middle‐aged US males of predominately Anglo‐Saxon ancestry with complete substance use and imaging data. Subjects with a history of stroke or traumatic brain injury were excluded."
The test used Magnetic resonance imaging (MRI) to measure seven subcortical regions, including: thalamus, caudate nucleus, putamen, pallidum, hippocampus, amygdala and nucleus accumbens. Measurements recorded alcohol and nicotine use, as well as maximum cannabis usage in the young adults, and regular cannabis usage among the middle-aged participants.
The study ultimately concluded that no damage or harmful effects were noted in the measured regions after cannabis use. The study states, "Cannabis use was unrelated to any subcortical ROI (region of interest). However, maximum nicotine use was associated with significantly smaller thalamus volumes in middle‐aged males."
While it would appear that this new study provides plenty of damning evidence about the damaging effects of alcohol and nicotine usage, marijuana users seem to be in the clear. Naturally, this study is just one of many that has been (or will be) conducted about the brain and cannabis use. More studies need to be completed, but the United States will have to loosen their rules and regulations about marijuana before that can happen.
Cannabis is a Schedule I substance, according to the U.S. Controlled Substances Act. This means that the DEA considers marijuana to have no medicinal value, and a high potential for abuse. There has been talk of changing that designation in September, thanks to a recently FDA-approved marijuana-derived drug, Epidiolex. But until that de-scheduling happens, and restrictions about conducting scientific studies are lifted, marijuana research like this study will be somewhat limited.