Cannabis use in teens does not affect their IQ or educational performance (news– 2016) https://uk.news.yahoo.com/cannabis-teens-does-not-... "Cannabis does not affect the IQ or educational performance of teenagers, a study has concluded. Published in the Journal of Psychopharmacology, UK researchers looked at 2,235 teenagers who took part in the Avon Longitudinal Study of Parents and Children to establish the effect of marijuana use on intelligence at the age of 15. There has been widespread debate on how cannabis affects intellectual and educational performance in adolescents. Previous research had shown teenage cannabis users have lower IQ scores and poorer educational outcomes than those who did not use the drug. However, the latest study notes these studies also show that teenage cannabis users tend to have higher rates of behavioural problems, depressive symptoms and were more likely to smoke cigarettes and drink alcohol. Their mothers were also more likely to have used cannabis during pregnancy. To find if there was a link between cannabis use and a lower IQ, the researchers adjusted the findings to take these factors into account.And after full adjustment, they found teens who had used cannabis did not differ from those who had never used it on either IQ or educational performance. "Cannabis use by the age of 15 did not predict either lower teenage IQ scores or poorer educational performance," they wrote. "These findings therefore suggest that cannabis use at the modest levels used by this sample of teenagers is not by itself causally related to cognitive impairment. Instead, our findings imply that previously reported associations between adolescent cannabis use and poorer intellectual and educational outcomes may be confounded to a significant degree by related factors." They concluded that teenage cannabis use may have less of a cognitive impact than other epidemiological surveys had previously suggested." (snipped) The article is based on "Are IQ and educational outcomes in teenagers related to their cannabis use? A prospective cohort study" http://jop.sagepub.com/content/early/2016/01/06/02... Just one last little quote- Do you know what WAS associated with an IQ drop in cannabis users and non-users in this study? Tobacco! "Further, cumulative cigarette use remained negatively associated with both outcomes in the fully adjusted models. Those who had used cigarettes >100 times were estimated to have an age 15 adjusted IQ 3.2 points lower (p=0.018) and an adjusted educational score 7.4 percentage points lower (p<0.001) than never-users of cigarettes (see Tables S3 and S4)." Less than 100 cigarettes = losing 3.2 IQ point and getting poorer grades! Granny