Feeling down in the dumps this time of year is no surprise; the sparkle of Christmas is gone, it's dark when you leave the house and it's dark when you get home again, and you've got the long old haul of the new year ahead of you.
But for some people, these feelings of misery are more than just a low mood - they're suffering from Seasonal Affective Disorder (SAD).
SAD is a disorder recognised clinically as a form of depression. While no specific cause has ever been confirmed, it's believed the onset is often triggered by reduced daylight hours and therefore less vitamin D, which in turn can result in low moods. But a professor in psychology has his own theory about exactly who gets affected in this way - and it's all to do with eye colour.
Lance Workman, a Professor of Psychology at the University of South Wales, carried out his own study in order to investigate his theory that there's a link between certain eye colours and susceptibility to SAD. According to Workman, people with brown eyes may be more likely to suffer from the seasonal disorder than those with lighter coloured eyes, and his small study appeared to back this notion up.
The research involved a sample of 175 students from two universities (one in South Wales, and the other in Cyprus) carrying out a seasonal pattern assessment questionnaire. This questionnaire is typically used to diagnose SAD in a person, and to determine the severity of their winter-time depression. After analysing the participants' results, Workman found that those with light or blue eyes scored significantly lower than those with dark or brown eyes, indicating lesser levels of SAD.
While this is only a very small study, and would need to be broadened to a far larger pool of participants if any sweeping statements were going to be made, it certainly backs up the professor's theory about eye colour having a link to SAD.
So why might eye colour impact your likelihood of SAD?
This is the burning question, but it's one Professor Workman believes he's got the scientific answer to. Writing for The Conversation, the expert explained it could be "because of the amount of light an individual’s eyes can process".
If you have brown eyes, you need to absorb more light in order to see than a person with blue or grey eyes would. When light enters the eye, a message is sent to the brain's hypothalamus (the part of the brain that secretes hormones and regulates mood, as well as temperature, hunger, sleep and other things) about how bright the light is. The more light the hypothalamus registers, the more melatonin it releases (that's the hormone which helps you to sleep).
In lighter-eyed people, they will release less melatonin but more cortisol during the winter, which Workman believes "might provide [them] with some resilience to seasonal affective disorder".
Got all that? The lighter your eyes, the less likely you are to suffer from SAD - in theory. And if you had to re-read it 14 times to properly understand why, let's just blame it on the January brain, shall we?
Read Lance Workman's full article on The Conversation here.
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