Do you find that your mood varies with the seasons? Feeling a little down in the winter months is a common problem. Millions of people suffer from a disorder known as seasonal affective disorder. In this disorder, low levels of light in the winter can actually make people physically and mentally ill. Although there are ways to treat seasonal affective disorder, many people still feel a little off during cold weather months. Exactly what causes this disorder? Although this, as with many circadian disorders, is not entirely known, eye color and gender both appear to play a role in seasonal affective disorder risk.

What Is Seasonal Affective Disorder?

Seasonal affective disorder, also known as SAD, is more than just the winter blues. People who suffer from this disorder often have a wide range of symptoms, including:

• changes in sleeping habits and appetite
• weight gain or loss
• an increase in pain, especially chronic pain
• fatigue and sleepiness
• difficulty with memory and concentration
• changes in sex drive
• depression and anxiety
• increase in anger and irritability
• feeling sad or hopeless
• changes in libido

Seasonal affective disorder is more common in people who live in far northern or far southern latitudes, where there are marketed differences between seasons. Symptoms usually start in the fall as nights become shorter, letting up in the spring when the sun comes out again in full force. Although only 1-2 percent of people have full-blown SAD, around 10-20 percent of us have some symptoms.

Gender and Seasonal Affective Disorder Risk

For reasons we do not entirely understand, women are more prone to SAD than men. This is true even after accounting for differences in lifestyle and activity levels. Women, in particular, are more likely to experience feelings of sadness, fatigue and a lack of pleasure in activities they formerly enjoyed.

This may be due to an interaction between female hormones and genes that regulate the circadian rhythm or almost any factor. While the cause is unknown, the relationship between gender and SAD is clear. In addition, the risk of seasonal affective disorder appears to be especially high among women of childbearing age.

Could Eye Color Affect Your Risk?

Gender is not the only in-born factor that can affect SAD risk. Eye color also appears to contribute. Researchers polled a large group of young people about their symptoms of seasonal affective disorder as well as various physical characteristics. Women reported more symptoms as did people with darker colored eyes.

How can eye color affect SAD risk? The answer lies in the way our brain regulates our circadian rhythm. Much of our internal rhythms are determined by light levels. When our retinas sense late, they send messages to the hypothalamus of the brain to produce less melatonin. Low levels of light in the winter can cause melatonin to be produced when it is not needed or in irregular levels. As a result, the circadian rhythm can become dysregulated. Brown eyes are less sensitive to light due to the high levels of melanin that produce their color. As a result, people with brown eyes are more sensitive to the cold-weather lack of light.

Blue eyes are more common in populations that originated in far northern latitudes. It is possible that people evolved to have blue eyes in part as a way of protecting the body from the ravages of SAD. New research will hopefully shed more light on the exact mechanism underlying the impact of eye color on SAD risk. Until we can identify and treat root causes, there are several ways to effectively reduce its impact on your mood and your life.

Warding Away the Winter Blues

Dealing with the symptoms of SAD can be devastating. However, there are ways to reduce the impact. Doctors recommend exposure to bright artificial light during the day, especially light in blue wavelengths. In addition, taking melatonin supplements at night can help keep the circadian rhythm on track.

Last, people with severe cases can take antidepressant medications or undergo specialized psychotherapy to help them keep their mood high even in dark winter weather. It is important to ask for help if you find yourself in figurative dark times.

Seasonal affective disorder is common, and apparently even more common for brown-eyed women and girls. While this circadian disorder can have devastating symptoms, these often can be reduced with a few simple lifestyle changes. Although winter is a dark time for many people, there is plenty of (often artificial) light to be found.