The study found that 10th and 12thgrade use in Colorado increased significantly after medical marijuana.
The study did not look at recreational marijuana
The study did not look at marijuana use over an extended period of time....read more on link
Links
[1] https://learnaboutsam.org/sam-statement-on-june-2015-medical-marijuana-study-published-in-lancet-psychiatry/
[2] http://www.rethinkpot.org/tags/lancet
[3] http://www.rethinkpot.org/tags/study