January is rarely anyone’s favourite month. With the festive buzz of the Christmas break a distant memory, the return to day-to-day life and responsibilities – coupled with depleted bank balances and miserable weather – mean that the start of the year is often a time when our mood dips to a low.
For some, however, it’s more than just a bump back down to reality – seasonal affective disorder (SAD) is a clinically recognised form of depression, which affects as many as one in 15 people in the UK between September and April.
There are many existing arguments about what might cause the condition to occur in certain people and not others, but now new research has suggested that in some cases, it could be a case of genetics – and as specific as the colour of your eyes.
The study, conducted by Lance Workman, a Professor of Psychology at the University of South Wales, used a sample of 175 students to test the theory, and found that people with light or blue eyes scored significantly lower on the seasonal pattern assessment questionnaire – the questionnaire often used to diagnose SAD – than those with dark or brown eyes.
‘These results agree with previous research which found that brown or dark-eyed people were significantly more depressed than those with blue eyes,’ Workman noted in an article on the subject written for The Conversation.
‘The reason that eye colour may make some people more susceptible to depression or mood changes might be because of the amount of light an individual’s eyes can process.’
The scale of the research was relatively small – meaning that more in-depth work would be required to conclusively prove or disprove the idea that people with brown eyes are more susceptible to SAD – but the science behind it does make sense.
When light enters the eye, a message is sent to your hypothalamus, which secretes hormones (such as oxytocin) that regulate temperature, hunger and sleep cycles about how bright that light is. As the amount of light reaching the hypothalamus increases, the amount of melatonin – the hormone that helps you to sleep – decreases. Lighter blue or grey eyes are more sensitive to light – and so ‘this mechanism might provide light-eyed people with some resilience to seasonal affective disorder (though a smaller proportion may still experience SAD),’ Workman explained.
‘People with SAD are advised to consult a GP regardless, he added, ‘especially if their symptoms do not improve, or if the condition becomes difficult to manage.’