Two studies have been released recently in JAMA Psychiatry that provide little evidence to support claims that marijuana has a harmful impact on the developing brain.
The first study analyzed pairs of siblings, one of which was exposed to marijuana and one of which was not. The results concluded that any differences "were attributed to common predispositional factors, genetic or environmential in origin." In addition, there was "no evidence for the causal influence of cannabis exposure" on the development of the brain.
The second study sought to find out whether the use of cannabis in adolescence changes the brain in a way that increases the risk of developing schizophrenia. A link existed among males who already had a high genetic predisposition toward schizophrenia, but there was no link among males who were at low risk of developing the disease or among females in either category. This disputes the claim that marijuana use directly causes schizophrenia.
To learn more about these significant studies, read this article on the Daily Chronic.