New NIDA-funded research shows that heavy marijuana use (at least four times per week over the past six months) is linked to adverse changes in the function and structure of brain areas associated with reward, decision making, and motivation. Heavy marijuana use can also enhance some brain circuits – possibly to compensate for reduced function in specific brain regions. This effect was more pronounced in those who started using at a young age, indicating that developing brains are particularly vulnerable to marijuana’s effects.
Although further long-term studies are needed to determine whether marijuana caused these effects, these scientific findings add to the growing literature showing that heavy marijuana use may harm the brain.
For a copy of the abstract (published online November 10), go to www.pnas.org/content/early/2014/11/05/1415297111.abstract.