Ever since junior highschool, when I had to do a class speech and I chose marijuana because my mom at the time was doing some early childhood course and had pamphlets on the topic - I have had it ingrained in my head that marijuana depletes fatty tissue from your body and so this means it eats away at your brain (and reproductive cells) because those organs are largely made up of lipids. I don't know how accurate that is, but that's what I read in those pamphlets and that's what I talked about in my speech to convey some of the repercussions of smoking cannabis. (As a side note, I was terrified during the whole speech and can never forget that the class clown sitting in the back was making smoking gestures throughout my whole speech)
The persistent, dependent use of marijuana during adolescence has been linked to later declines in an individual's intelligence, attention and memory, according to a large, New Zealand-based study. http://www.nzdoctor.co.nz/un-doctored/2012/august-2012/28/cannabis-use-a
This is excerpt is directly from the study:
Recent reports show that fewer adolescents believe that regular cannabis use is harmful to health. Concomitantly, adolescents are initiating cannabis use at younger ages, and more adolescents are using cannabis on a daily basis. The purpose of the present study was to test the association between persistent cannabis use and neuropsychological decline and determine whether decline is concentrated among adolescent-onset cannabis users. Participants were members of the Dunedin Study, a prospective study of a birth cohort of 1,037 individuals followed from birth (1972/1973) to age 38 y. Cannabis use was ascertained in interviews at ages 18, 21, 26, 32, and 38 y. Neuropsychological testing was conducted at age 13 y, before initiation of cannabis use, and again at age 38 y, after a pattern of persistent cannabis use had developed. Persistent cannabis use was associated with neuropsychological decline broadly across domains of functioning, even after controlling for years of education. Informants also reported noticing more cognitive problems for persistent cannabis users. Impairment was concentrated among adolescent-onset cannabis users, with more persistent use associated with greater decline. Further, cessation of cannabis use did not fully restore neuropsychological functioning among adolescent-onset cannabis users. Findings are suggestive of a neurotoxic effect of cannabis on the adolescent brain and highlight the importance of prevention and policy efforts targeting adolescents.