Update: The Latest Research about Cannabis and the Brain

Photo Credit: High Times Magazine

Photo Credit: High Times Magazine

When it comes to cannabis and the brain, research seems to conflict on all sides of the spectrum as to whether or not smoking marijuana increases or decreases the volume of grey matter in the brain. Now, researchers from the Netherlands suggest heavy cannabis consumption doesn't shrink grey matter volumes, and in fact one region shrank less over time in marijuana smokers than in those that abstained from cannabis use. The researchers realized that all of the conflicting studies looked at cross-sectional studies analyzing brain volumes, but that these studies only represent one moment in time and cannot prove causality. Therefor,e they decided to conduct a longitudinal experiment in order to show cannabis' affects on the brain over a period of time. The study involved 33 marijuana smokers and 43 "healthy controls" who regularly underwent MRI's. The study began with the average age of participants was 20, and ended when the average age reached 24. Although many dropped out of or were excluded from the experiment, the sample remained large enough for researchers to draw conclusions about marijuana use on the brain.

Researchers concluded cannabis use did not change grey matter morphology. While they did not observe a reduction in grey matter volumes, cross-sections did show cannabis consumers had less grey matter in their medial-temporal lobes. One issue is that researchers were unable to observe their subjects when they began to smoke marijuana, so they don't know whether or not reduced volume in medial-temporal lobe grey matter increased the likelihood of cannabis consumption, or if cannabis consumption resulted in reduced volume. Many of the smokers started out with a slightly smaller medial-temporal lobe. On the other hand, marijuana consumers had larger cerebelli, suggesting cannabis may be able to prevent the shrinkage of the cerebellum that naturally occurs with age. Despite this, previous studies have clearly suggested that cannabis use in early adolescence negatively impacts the white matter of the brain, and that the "age of initiation" determines the severity of the disturbances. 

This information was provided by High Times Magazine and approved by our Chief Medical Officer.