According to the National Institute on Drug Abuse, of all the illicit substances, marijuana is the most commonly abused among adolescents and young adults, and abuse during adolescence increases the likelihood of dependency in adulthood. In a study published in the American Journal of Medical Genetics Part B (Neuropsychiatric Genetics), researchers found that variants in the CB1 gene—the brain target for the psychoactive ingredient in marijuana—may be associated with one or more symptoms of marijuana dependence in adolescents.
Led by Dr Christian Hopfer of the University of Colorado, the researchers collected DNA samples from 541 youths aged 17 years or older who had recently used marijuana at least 5 times. The youths were interviewed for symptoms of dependence using the Composite International Diagnostic Interview- Substance Abuse Module and 327 were found to have one or more symptoms of dependence. The 214 who had no symptoms became controls.
Two CB1 variants (present in 12% of the general population) were significantly linked to the likelihood of the development of one or more dependent symptoms, while only one CB1 variant (present in 21% of the general population) was linked to a lower risk of the development of dependent symptoms.
The researchers acknowledged that multiple genes and the way they interact with the environment might also influence marijuana dependence, as well as other addictions. They called for future studies to examine the variants of other drug-related traits and additional DNA sequence variations for possible associations with drug abuse.