The dose-dependent toxicity of the main psychoactive component of cannabis in brain regions rich in cannabinoid CB1 receptors is well known in animal studies. However, research in humans does not show common findings across studies regarding the brain regions that are affected after long-term exposure to cannabis.
Cannabis can regrow brain cells, so the argument goes. It’s become a favorite claim for supporters of medical weed, but there’s a catch.
When you look at these studies going back years, you see that one study will report that marijuana use is related to a reduction in the volume of the hippocampus [a region of the brain associated with memory and emotions