The evidence of harm [4], however, is only getting clearing. And the latest rise in use, addiction and death by car crash numbers add clarity to the picture of harms associated with widespread use of the drug.
Links
[1] http://marijuana-policy.org/manufacturing-addicts-marijuana-use-doubles-among-us-adults/
[2] http://www.rethinkpot.org/tags/legalization
[3] http://www.rethinkpot.org/tags/usage
[4] http://marijuana-policy.org/pot-used-to-be-pretty-harmless-but-its-plenty-dangerous-today-post-gazette/