New research shows that specific variations in the cannabis receptor gene (CB1) may be associated with the development of one or more symptoms of marijuana dependence in adolescents. This is one of the first studies looking specifically at the link between marijuana dependence and CB1 variations.

Background: Marijuana is the most commonly abused illegal substance among adolescents and young adults, and those who begin using at this stage are about twice as likely as adults to become dependent. Genetic variations in the CB1 receptor—the brain target for the psychoactive ingredient in marijuana—is a logical candidate gene to study as a potential contributor to vulnerability to marijuana dependence. Therefore, researchers examined the associations between specific variants in the CB1 gene and the rates of marijuana dependence.

Study Design: The scientists collected DNA from 541 youths aged 17 or older who had used marijuana at least five times recently. After interviews to identify one or more DSM-IV symptoms of dependence, 327 were established as cases; the remaining 214 had no symptoms and served as controls. All subjects were genotyped for four specific DNA sequence variations of the CB1 gene.

What They Found: One CB1 variant (found in 21 percent of the general population) was associated with a lower rate of having one or more marijuana dependence symptoms, while two others (present in 12 percent of the general population) were linked to increased likelihood of developing dependence symptoms.

Comments from the Authors: Identifying gene variants that may afford some protection against marijuana dependence may have important implications for intervention. However, it is likely that multiple genes and their interactions with environmental events influence marijuana and other drug addictions. Therefore, some level of genetic protection may not necessarily protect an adolescent from becoming dependent on drugs or suffering other related health consequences.

What’s Next: Future studies should examine these genetic variants for other drug-related traits, as well as additional DNA sequence variations for possible drug abuse associations.

Publication: The study, led by Dr. Christian J. Hopfer of the University of Colorado, was published in volume 141B, pages 895-901 (2006) of the American Journal of Medical Genetics Part B (Neuropsychiatric Genetics).

Source:NIDA Newscan 27th Aug. 2007