This study found that chronic marijuana use in adolescence was negatively associated with achieving important developmental milestones in young adulthood.
Links
[1] http://www.courant.com/politics/hc-news-teen-pot-booze-study-20171106-story.html
[2] http://rethinkpot.org/tags/youth
[3] http://rethinkpot.org/tags/chronic