Regular marijuana use has a negative impact on teen brains according to researchers. Psychologists at the American Psychological Association’s 122nd Annual Convention cited several recent studies showing the harmful aspect of regular marijuana use on teen brains.

By regular use, the researchers mean once a week and say that level of use is dangerous. Tests show that teens who use marijuana regularly can lose up to six IQ points before adulthood. Brain scans show significant changes to the still developing brain structure, including abnormalities in the brain’s grey matter. Read more: Regular marijuana use bad for teens’ brains