Scientists have found in a study of tobacco users that their drinking behavior is linked to some of the same chromosome regions associated with alcohol addiction.
The study, published in the December issue of the journal Alcoholism: Clinical & Experimental Research, offers evidence that the interaction between smoking and alcohol consumption may partly be due to overlapping genetic risk factors. The results also provide further confirmation that alcoholism is a complex behavior drawing from both environmental and genetic factors.
"Since we know that people who drink often smoke and that smokers often drink, we thought it reasonable to collect some information about the drinking behavior in these families," said lead study author Dr. Kirk C. Wilhelmsen, associate professor in the departments of genetics and neurology at the University of North Carolina at Chapel Hill's School of Medicine.
He also is a member of the Carolina Center for Genome Sciences, the Bowles Center for Alcohol Studies and the UNC Lineberger Comprehensive Cancer Center.
The research team studied 158 families that had at least two first-degree relatives who had smoked 100 or more cigarettes in their lifetime. These included any combination of parents, siblings and offspring who had smoked.
A detailed questionnaire was used to search for alcohol-related behavioral traits, or phenotypes, shared within each family. Questions concerned the quantity of alcohol consumed, such as the number of alcohol drinks per month for six consecutive months and the number of alcohol of drinks consumed in a typical week and typical day.
DNA from blood samples taken from each family participant was analyzed for particular genetic variations. "We looked for excess chromosome sharing of regions that had genes that affect patterns of drinking behavior," Wilhelmsen said.
The researchers applied linkage analysis, which examines differences, or variants, in the DNA sequences of the chromosomes inherited from one's parents. These gene variants determine, in part, many human characteristics, such as a propensity to drinking behavior, Wilhelmsen said. "And when you see aggregation of behavioral traits in families, it can be due to genetics."