The researchers . . . compared the genetic makeup of the problematic Internet users with that of healthy control individuals. This showed that the 132 [Internet addicts] . . . are more often carriers of a genetic variation [on the CHRNA4 gene that changes the genetic makeup for the Alpha 4 subunit on the nicotinic acetylcholine receptor] that also plays a major role in nicotine addiction. "What we already know about the nicotinic acetylcholine receptor in the brain is that a mutation on the related gene promotes addictive behavior," explains Dr. Montag. Nicotine from tobacco fits -- just like acetylcholine, which is produced by the body -- like a key into this receptor. Both these neurotransmitters play a significant role in activating the brain's reward system. "It seems that this connection is not only essential for nicotine addiction, but also for Internet addiction," reports the Bonn psychologist.
The abstract states:
Recent studies from Asia provided first evidence for a molecular genetic link between serotonergic and dopaminergic neurotransmission and Internet addiction. The present report offers data on a new candidate gene in the investigation of Internet addiction—the gene coding for the nicotinic acetylcholine receptor subunit alpha 4 (CHRNA4). A case-control study was carried out. The participants were recruited from a large gene data bank, including people from the general population and from a university setting. A total of 132 participants with problematic Internet use and 132 age- and sex-matched controls participated in the study. Participants provided DNA samples and filled in the Internet Addiction Test Questionnaire. The T- variant (CC genotype) of the rs1044396 polymorphism on the CHRNA4 gene occurred significantly more frequently in the case group. Further analyses revealed that this effect was driven by females. Combined with the findings from other studies, the present data point in the direction that rs1044396 exerts pleiotropic effects on a vast range of behaviors, including cognition, emotion, and addiction.
Other questions naturally follow and will have to be answered by those who can get behind the paywall or in future studies.
What are the raw numbers of percentages of persons with or without the gene mutation? What is the statistical signficance of this finding and how does it compare with the referenced prior study of the same gene? Are there look elsewhere effects from other studies done with the same methods drawn from the same gene data bank that weren't reported? Why is this gene more important in women than in men and does that confirm prior research?
Is this receptor and the associated genetic mutation implicated in other mental health conditions? Are there additions that have distinct genetic and biochemical pathways that have nothing to do with this receptor and genetic mutation? Are there therapies that target this biochemical pathway, either cognitive or drug based? Are their benefits that come with the vulnerability to addiction? Is the gene linked to a personality type?
The study is Christian Montag, Peter Kirsch, Carina Sauer, Sebastian Markett, Martin Reuter. The Role of the CHRNA4 Gene in Internet Addiction. Journal of Addiction Medicine, 2012; 6 (3): 191 DOI: 10.1097/ADM.0b013e31825ba7e7