Genes Play Important Role in Risk for Dependence on Illicit and Licit Drugs
Monday, Nov. 5, 2007
Videoclip 1: "We did not find any single vulnerability."
Videoclip 2: "We inherit vulnerability to using alcohol or drugs."
Videoclip 3: "This may help us target interventions."
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,
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.
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."
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.
pairs that participated were from the Virginia Adult Twin Study of Psychiatric
and Substance Use Disorders. These twin pairs were ascertained from the
Virginia Twin Registry. The Virginia Twin Registry, now part of the VCU Mid-Atlantic Twin Registry, contains a
population-based record of twins from Virginia, North Carolina and South Carolina.
"This study also confirmed the
strong role that genetic factors play in influencing our vulnerability to drug
abuse and dependence," Kendler said. Heritability – the proportion of
individual differences in risk due to genetic differences – was estimated in
this study to be more than 70 percent for cocaine, cannabis and nicotine A/D,
nearly 60 percent for alcohol A/D, and, interestingly, quite a bit lower –
around 35 percent – for caffeine A/D, he said.
In previous studies, researchers examined
an array of illegal substances and did not include commonly used licit drugs,
and included only male participates. This was the first study of its kind to
examine across the sexes and degree to which risk factors for dependence were
shared between illicit and licit drugs.
This work was supported by grants from the National Institutes
Kendler collaborated with John Meyer, M.S., from the
Department of Psychiatry at VCU; and Carol A. Prescott, Ph.D., from the
Department of Psychology, University of Southern
About VCU and VCU Medical Center
Virginia Commonwealth University is a major, urban public research university with national and international rankings in sponsored research. Located in downtown Richmond, VCU enrolls more than 31,000 students in 226 degree and certificate programs in the arts, sciences and humanities. Sixty-seven of the programs are unique in Virginia, many of them crossing the disciplines of VCU’s 13 schools and one college. MCV Hospitals and the health sciences schools of Virginia Commonwealth University comprise VCU Medical Center, one of the nation’s leading academic medical centers. For more, see www.vcu.edu.