US researchers have identified a gene linked to alcoholism and depression, the first to be associated with both conditions. Scientists at the Washington University School of Medicine think that variations in a gene called CHRM2 either increase or decrease the likelihood that a person will be affected by one or both of the disorders. Previous studies of twins and adopted siblings have showed that alcoholism and depression both seem to run in families, suggesting that they share common genetic factors. 'Clinicians have observed a connection between these two disorders for years, so we are excited to have found what could be a molecular underpinning for that association', said team leader Alison Goate.
The research, reported in the journal Human Molecular Genetics, is part of the ongoing US Collaborative Study on the Genetics of Alcoholism (COGA). This project involves the collection of interview responses and DNA samples from over 10,000 people with alcohol dependence and their families. In the latest study, the Washington University team looked at DNA from 2,310 people from 262 families in which at least three members were affected by alcoholism. They then looked at the COGA participants affected by depression, and found that both these approaches pinpointed the same region of chromosome seven. The region contained the already-known CHRM2 gene, which is involved in key brain functions such as attention and memory.
The researchers are now waiting to see if their findings are the same in another group of people under study. Peter McGuffin, a geneticist working at King's College in London, says that if Goate's work is replicated by other groups, it will provide another potential target for developing new drugs for treating depression and alcoholism. Both disorders are thought to be caused by a combination of susceptibility genes and environmental risk factors.