Extensive twin study finds no link between marijuana use and IQ decline in teens

The largest ever longitudinal twin study involving more than 3,000 adolescents from around the world has found little evidence to suggest that adolescent marijuana use has a direct effect on intellectual decline.
Read more: http://snapzu.com/kxh/extensive-twin-study-finds-no-link-between-marijuana-use-and-iq-decline-in-teens