Marijuana is the most used recreational drug in the United States. The purpose of the present study was to examine the associations of Marijuana use with changes in intellectual performance. Different test and approaches were made, and studies show in two longitudinal studies of adolescent twins ranging ages from 9-12, before Marijuana involvement and ages ranging from 17-20, Marijauna users had lower test scores relative to nonusers and showed significant decline in dose-response relationship between frequency of use and intelligence quotient (IQ) change. Furthermore, Marijuana-using twins failed to show significantly greater IQ decline relative to their abstinent siblings. Evidence from these two samples suggests that observed declines in measured IQ may not be a direct result of Marijuana exposure but rather attributable to familiar factors that underlie both Marijuana initiation and low intellectual attainment.

Source info: N.p., n.d. Web. 

N.p., n.d. Web.