The eyes may be the window to more than just your soul: They could in fact be an important clue to your risk for alcohol dependence. That’s according to a new study from researchers at the University of Vermont, published in the July 2015 issue of the American Journal of Medical Genetics: Neuropsychiatric Genetics (Part B).
Researchers found that European Americans with light-colored eyes – specifically, blue, green or grey eyes – had a higher prevalence of alcoholism than people with brown eyes. And among those with light eyes, blue-eyed individuals stood out as most statistically likely to have alcohol dependency issues. About one in six people have blue eyes.
Lead researcher Dawei Li, PhD, and his colleagues studied a group of 1,263 European Americans. “We observed that individuals with light eye color had a higher prevalence of alcohol dependence than those with darker eye color in our research samples,” Dr. Li, an assistant professor in the department of microbiology and molecular genetics at the University of Vermont (UVM) in Burlington, tells Addiction.com. “We also found instances … where the eye color gene and alcohol-dependence-associated gene are physically located close on the same chromosome,” he says. What that means is that “the closer the two genes, the higher the chance they can be inherited together by generations.” Lastly, Li observed statistical evidence using an existing database that genes for alcoholism and genes for eye color may interact with one another.
Overall, these findings suggest that eye color may be a potential indicator of risk for alcohol dependence in European Americans, Li says. European Americans include any Americans with ancestors originating in European countries. Blue-colored eyes are more common in northern European countries than anywhere else in the world, the study says. Northern European countries include Sweden, Denmark, Norway, Finland, Estonia, Iceland, Ireland and the United Kingdom.
Those Baby Blues Aren’t Your Fate
Having light eyes doesn’t mean you’re destined to have issues with alcohol, of course. “Genetic factors of addiction don’t act alone; environmental exposure or cultural factors play a crucial role,” stresses Li. “As with most complex human disorders, we believe both nature and nurture play a role in addiction. It’s not clear to us at this stage whether this association is driven by genetics, culture or behavior,” he says, noting that more research is needed. So it could be, for example, that alcohol is a big part of your family traditions and you’re exposed to lots of drinking at a younger age by family members who happen to share your blue- or green-eyed peepers.
Eye color is determined by multiple genes. The number and size of melanin particles in a person’s eyes influences whether the eyes are darker or lighter; blue eyes have the least amount of melanin particles, followed by gray, green, hazel and brown, which has the most melanin.
Li’s finding is far from the first to link eye color to differences among people. Other research has found that people with different eye colors have different reaction time, personality, agreeableness, motor skills and even drug sensitivity. A 1999 study found, in fact, that darker-eyed people are more sensitive to alcohol than are the light-eyed. The UVM study also makes note of other scientific literature that had found people with light-colored eyes are at higher risk for seasonal affective disorder (SAD) when exposed to varying light intensities because light-eyed people are more sensitive to light changes. SAD, in turn, is associated with alcohol dependence.
Li says he’ll continue his research in hopes of finding a more precise connection between genes and mental illness (which includes addiction), as well as how eye color actually contributes to the risk for alcoholism and other issues. For now, “this [research] suggests an intriguing possibility: that eye color can be useful information to assist alcohol dependence diagnosis,” adds Arvis Sulovari, a doctoral student at UVM who worked alongside Li on the research.