An increasing amount of research has linked the color of your eyes to your risk of a number of health concerns – and alcoholism is the latest reveal
When you look into someone’s eyes, what do you see? Their soul? What they’re thinking? Or maybe even something about their health?
A new study published in the American Journal of Medical Genetics parsed the question: Can eye color be a useful clinical indicator of alcoholism and possibly other psychiatric illnesses?
How is eye color linked to alcohol dependence?
The researchers, Arvis Sulovari and Dawei Li, Ph.D., studied people of European or African ancestry who had at least one mental health illness. Many individuals had multiple illnesses, including depression, bipolar disorder, schizophrenia and addiction to either alcohol or drugs.
From that database, Sulovari and Li filtered out 1, 263 Europeans with alcohol dependence as their sample population and controlled for population stratification. Age, gender, and different ethnic or geographic backgrounds were compared.
The duo found that individuals with lighter eye colors – including green, grey or brown in the center – had a higher incidence of dependence on alcohol than those who had brown eyes.
After noting the eye-color connection with blue eyes as a risk factor compared to brown eyes, the researchers found a statistically significant interaction between eye color and alcohol-dependence associated genes. The genetic components of both eye color and alcohol dependence lined up along the same chromosome.
In a press release, Li said his work with Sulavari provided a strong stepping-stone – though he pointed out that more research is needed as “we still don’t know the reason” for these associations.
According to the University of Vermont, the study results suggested hope in finding not only the roots of alcoholism but also many other psychiatric illnesses.
A 2000 archival study published in the journal Personality and Individual differences suggested similar results, with the results indicating that lighter-eyed individuals were more likely to become dependent on alcohol than those with darker eyes. The authors concluded that darker-eyed individuals were more drug and alcohol sensitive and therefore needed less alcohol to feel effects that took longer in lighter-eyed individuals.
Where does eye color come from?
Eye color is controlled by as many as 15 genes associated with eye color inheritance, with one of the genes located on the X-chromosome, making it a partially sex-linked trait. The interactions and variations between several genes actually determine our eye color. Previously, it was thought that eye color came from one gene and that blue eyes were recessive to brown eyes, meaning if two parents had blue eyes they could not produce a brown eyed child.
Now we know that the color of the iris is determined by the amount and distribution of melanin or pigmentation in the layers of the iris. Light colored eyes have less melanin and will therefore appear blue, green or hazel due to the way the light is scattered in the collagen fibers of the iris.
What other conditions could the color of our eyes determine?
Research has linked eye color with various health concerns. According to Dr Jari Louhelainen, a senior lecturer in biomolecular sciences at Liverpool John Moores University, genes that determine our eye color do other things in the body. “’One of them, NCX-4, which is linked to darker eyes, controls many proteins, of which one has recently been linked to pain,” he explained in an article published in the Daily Mail.
Additionally, Inna Belford, MD., Ph.D., a professor of anesthesiology at Pittsburgh University, linked eye color to pain at the American Pain Society (APS) 33rd annual scientific meeting in Tampa, Florida
Dr. Belford studied the association of eye color and pain-related traits among 58 healthy women who were giving birth . Her study found that women with lighter-colored eyes – blue or green- experienced less pain during childbirth than women with brown or hazel eyes. The lighter-eyed women also experienced less anxiety, depression, and negative thoughts after delivering their babies than women with dark eyes.
Blue eyes and macular degeneration
Blue eyes may also increase your risk of blindness from macular degeneration, according to Scottish researchers. Lighter eyes, such as blue and green, contain less of a macular pigment believed to protect against macular degeneration, an incurable eye disease.
Also, an Australian study found that darker eyes had up to 2.5 times the risk for developing cataracts than those with lighter eyes. The theory offered is that dark eyes absorb sunlight, much like wearing dark clothing in the summer. Sunlight exposure is thought to increase the temperature of the lens and therefore the risk of cataracts. However, the authors acknowledged that dark eyes were associated with an increased risk of cataracts even when not in the sun.
Eye color may also indicate anxiety levels
Your eye color could also be an indicator of anxiety levels – and this could be explained by the developmental relationship between eye color and anxiety. “The melanocytes, the cells involved in pigmentation and the ganglion cells in the autonomic nervous system, which are involved in your experience of anxiety both originate in the neural crest,” report Bassett and Dabbs Jr.
The authors cited a Caucasian children’s study demonstrating that behaviorally-inhibited children who withdrew from the unfamiliar, including situations or people, more often had blue eye than brown.
Where to from here?
If you’re concerned about your eye color and an increased risk of a health concern, it’s important to bear in mind that many of these statistics warrant further research – that is, there is more to them than meets the eye.
More importantly, you should have yearly eye exams to rule out health conditions that may be easily determined by the arteries, veins, optic nerve and sclera of the eyes. Your optometrist can assess your eyes for these conditions – and you should also visit your doctor regularly who can determine whether you are at risk for conditions such as high blood pressure, diabetes, liver disorders, cardiovascular disease, or other eye diseases.