Many scientific studies demonstrate the long-term effects of marijuana use. Last summer, for example, I documented a few examples from medical journals.

The British Journal of Psychiatry “reviewed four large studies, all of which showed a significant and consistent association between consumption of marijuana

(mostly during teenage years or early 20s) and the later development of schizophrenia.” Likewise a study published in the British medical journal Lancet

concluded that marijuana use increases the risk of young people developing psychotic illness, such as schizophrenia.

Earlier this month came the first study, done by researchers at Northwestern University, which examined the relationships between casual marijuana use and

brain changes. Their findings published in the Journal of Neuroscience, found “significant abnormalities in two important brain structures.” These abnormalities

in the working memory of your brain affect judgments, decisions, and planning.

It is worth mentioning the subjects of their study. Their sample of patients included young people between the ages of 18 and 25. The casual marijuana users

were compared to a group of well-match control subjects. Some used marijuana once or twice a week, while others used it every day. The researchers then

used MRIs to evaluate the brains of the participants.

Abnormalities were found in all of the marijuana users. They were also dose-dependent. That means that the changes were greater with the amount of

marijuana use. Future longitudinal studies might answer the question of whether the effects continue or decline if a marijuana user quits.

Because the brain regions affected are important in motivation, the studies confirm what many of us have noticed. Marijuana users become less oriented

toward goals and purpose in their life. They also seem less focused.

At the time when states like Colorado and Washington have legalized marijuana and other states are considering legalization, we are learning more about the

deleterious effects of marijuana use. Not only are long-time users affected, but casual users are also affected. Legislators should reconsider this issue.