The old anti-drug PSAs from the 80s and 90s used to suggest that if you chose to smoke marijuana, that meant you made dumb choices. It turns out that they could have made even more hyperbolic claims and still have been right: According to researchers from Northwestern University, regular marijuana use in teens leads memory issues later in life.

“Heavy” marijuana smokers (defined as those who smoked it daily for around three years) showed structural abnormalities in the areas of the brain related to working memory. They performed poorly when subjected to memory tasks, and poor memory is a predictor of poor academic performance and day-to-day function in general. The abnormalities are similar in appearance to those associated with schizophrenia.

“The study links the chronic use of marijuana to these concerning brain abnormalities that appear to last for at least a few years after people stop using it,” said lead study author Matthew Smith, an assistant research professor in psychiatry and behavioral sciences at Northwestern University Feinberg School of Medicine. “With the movement to decriminalize marijuana, we need more research to understand its effect on the brain.”

The study is the first of its kind in that it targeted key brain regions in the deep subcortical gray matter of chronic marijuana users with structural MRI and then correlated the abnormalities with an impaired working memory. Working memory is the ability to remember and process information in the moment and — if needed — transfer it to long-term memory. In computer terms, working memory is like a computers RAM, while long-term memory is akin to the computer’s hard drive. Few other studies have directly compared chronic marijuana use in otherwise healthy individuals and individuals with schizophrenia.

The study also reports that abnormalities are more pronounced the younger an individual was when they started their heavy marijuana consumption. This suggests that the regions of the brain related to memory are more susceptible to influence in the earlier stages of development.

A longitudinal study will be needed to definitively link marijuana use with memory impairment, as this study only examined individuals at a set moment in time. While It is possible that the abnormal brain structures reveal a pre-existing vulnerability to marijuana abuse, Smith said that evidence that the younger a subject started using the drug the greater his brain abnormality indicates marijuana may be the cause.

This has been your daily reminder that drugs are bad, kids.