The role of genetics in addiction has been debated for decades. Scientists and other health experts have successfully identified various risk factors for the development of addiction, but concise and objective predictors of drug addiction have eluded discovery. This past year, however, science has made significant strides in discerning how genetics may affect addiction.
A landmark scientific paper published in the April 2009 issue of Nature Reviews Genetics presented some groundbreaking new insights into the role of genetics in addiction by honing in on specific genes that are tied to all types of addictions. The study, conducted by addiction experts at the University of Virginia Health System and the University of Michigan, even found that some genes that are associated with alcohol dependence are also linked to various other addictions. The gene was found to be a common factor in addictions to nicotine, cocaine, opioids and other substances.
Study co-author Ming Li, Ph.D., professor of psychiatry and neurobehavioral sciences at the UVA School of Medicine, commented on the study and its potential impact:
“Addiction researchers have found that several genes are linked with multiple addictions. … So, we’re narrowing the scope to specific genetic targets. Once researchers can pinpoint exact genetic variants and molecular mechanisms, then we can create much more effective, even personalized, treatments for individuals addicted to a variety of substances.”
Li also believes that further research is needed to understand the full impact of genetic variations on addiction. “The exact nature of the gene variants and how they function are still unknown, so functional studies as well as studies using additional ethnic population samples may be quite revealing,” Dr. Li said.
Another recent study, conducted by researchers at the University of Colorado in Denver, pinpointed genetic pathways and genes associated with alcohol consumption. The researchers were able to identify genetic factors that predisposed both rats and humans to drink more; however, they were unable to discover a similar link between the genes and actual alcohol addiction. Nonetheless, according to Boris Tabakoff, a lead researcher, the study’s results may help scientists to eventually connect the dots between genetic makeup and addiction.
Tabakoff said, “We know that high levels of alcohol consumption can increase the risk of becoming alcohol dependent in those who have a genetic makeup that predisposes to dependence. This is a case of interaction between genes and environment. Indeed, in our study we found that, higher alcohol consumption in humans was positively correlated with alcohol dependence. However, because different sets of genes seem to influence the level of alcohol consumption, as opposed to propensity for alcohol dependence, we are confronted with great variation in humans. Individuals with a set of genes that predisposes them to drink moderate amounts of alcohol may still have the genetic predisposition to lose control over their drinking behavior, and perhaps become alcohol dependent. Conversely, individuals with a genetic predisposition to drink high amounts of alcohol may not have the genes that predispose them to become dependent.”
A study just completed at Brown University (the results will be published in the January 2010 issue of Alcoholism: Clinical & Experimental Research) succeeded in identifying a link between a gene variation and teen alcohol misuse. For the study, researchers examined the genetic makeup of 187 adolescents (98 boys and 89 girls) around the age of 15 years. They were able to correlate a polymorphism (variation in the shape) of the OPRM1 opioid receptor gene called A118G with heightened risk for alcohol-related problems and likelihood to meet the clinical diagnostic criteria for Alcohol Use Disorder (AUD).
Robert Miranda, Jr., assistant professor in the department of psychiatry and human behavior at Brown University and corresponding author for the study, commented on the implications of the study’s findings:
“Our current knowledge about the genetics of alcohol misuse during adolescence comes almost exclusively from family and twin studies. … But the relative importance of environmental and genetic factors appears to shift considerably over the course of adolescence … with genetics playing an important role once teenagers begin to drink. … Our findings provide the first evidence to suggest that teenagers who carry a certain variant of the OPRM1 gene experience more alcohol-related problems.”
Notably, the Brown University team discovered that teens with this variant were more likely to report drinking alcohol because of the pleasurable effects than for other reasons. The fact that the genetic variation enhances the pleasure experienced by youth when consuming alcohol helps to explain why teens with this variation might be more likely to develop problem drinking behaviors.
Miranda, Jr., explains, “The G allele, or variant, of the OPRMI gene is associated with the function of the body’s own natural opiate system. Research suggests that the G allele is associated with experiencing more pleasure and greater intoxication after drinking.”
By Emily Battaglia
