A study finds that [ people under 17 years old that use marijuana every day suffer various harmful effects ]( http://www.theguardian.com/society/2014/sep/10/teenagers-who-use-cannabis-every-day-60-less-likely-to-finish-school ) . I don't think this can justify prohibition, because prohibition hurts a much larger number of people.
Ссылка: https://stallman.org/archives/2014-jul-oct.html#11_September_2014_%28Effects_of_daily_marijuana_use%29