By Katy Walter
It is no secret that cannabis (also known marijuana) is a popular drug among young adults. Now, with the recent legalization of recreational marijuana in the states of Colorado and Washington (for those 21 and over), the drug is likely to become even more popular among teens due to the widespread belief among adolescents and adults that cannabis is a “safe” drug. (Hurd, Mihaelides, Miller & Justras-Aswad, 2013) However, scientific studies have shown that cannabis is not as harmless as it is perceived to be, especially for adolescents.
Adolescent brain structures are rapidly changing and therefore teens are more vulnerable than adults to cannabis’s negative effects. These may include mental disorders, like schizophrenia. Also worrisome, because most young adults are in school, is the correlation found between cannabis use and poor educational performance, which may be due to cannabis-caused cognitive or motivational deficits. (Verweij, Huizink, Agrawal, Martin & Lynskey, 2013).
In a few recent studies, researchers discovered that adolescent cannabis use may have long-term influence on behaviors associated with areas in the brain that are developing and changing during adolescence. Specifically, cannabis affects the reward pathway, which is central to decision-making and motivation, and areas involved in habit formation and motor function (Hurd et al, 2013). One study (Ellgren, Spano & Hurd, 2006) administered low-to-moderate THC (the main psychoactive chemical in cannabis) to adolescent rats (during days 28-49 after birth). They found that these rats exhibited enhanced heroin self-administration behavior during adulthood. The study supports the correlation between adolescent cannabis use and an increased risk of other drug use, also known as the “gateway effect.”
Another study, on humans, can perhaps offer an explanation for this effect: in this study, researchers compared the dopamine synthesis capacity (ability of the brain to send reward signals, or the pleasure you get from various experiences, such as eating your favorite food) of 19 regular cannabis users who began using cannabis in adolescence to 19 nonusers. They found that the users had lower dopamine synthesis capacity. In other words, the brains of the people who began using cannabis as young adults were unable to produce as many reward signals as the people who did not use cannabis (Bloomfield et al., 2013). The “gateway effect” could perhaps be because drugs amplify dopamine effects—potentially compensating for low dopamine synthesis capacity. However, it should be noted that genetic and environmental factors have an enormous influence on long-term negative effects of adolescent cannabis use (Hurd et al., 2013). (more…)