The genes that play a role in illegal drug abuse are not entirely the same as those involved in dependence on legal substances like alcohol and nicotine, and caffeine addiction appears to be genetically independent of all the others, according to a study led by Virginia Commonwealth University researchers.
The findings may guide efforts by researchers to use molecular genetic tools to localize genes that influence risk for psychoactive drug abuse or dependence, or A/D.
In the November issue of the Archives of General Psychiatry, a journal of the American Medical Association, researchers examined the degree to which genetic and environmental risk factors for dependence were shared between illicit and the more commonly used licit psychoactive drugs among men and women.
“We wanted to know whether there was a single set of genes that influence risk for A/D on all substances,” said Kenneth S. Kendler, M.D., a professor of psychiatry and human genetics in VCU's School of Medicine and lead author on the study.
“Our findings suggested two genetic factors - one which strongly impacted on risk for A/D of illicit drugs, such as cannabis and cocaine, and one that impacted on risk for A/D of licit drugs, including caffeine, nicotine and alcohol. However, these two factors were rather strongly correlated,” he said. “It was also of interest to note that the genes for caffeine A/D were pretty independent of those found for all the other substances.”
Kendler and his colleagues examined lifetime symptoms of abuse of and dependence on marijuana, cocaine, alcohol, caffeine and nicotine among 4,865 male-male and female-female twin pairs through a series of personal interviews. The data collected from the interviews was analyzed using the methods of structural equation modeling.