Well, we're now officially off daylight saving's time, so the days are now shortened with less light. I must admit even though this time comes around every year, the first few days definitely leave me a bit jolted. During the spring and summer, I got heavily used to running in the evenings, so with less light at this time, I have to readjust my body to afternoon running (I rarely run in the morning) when I find myself the most tired. I also have to be aware with less light, there is the issue of possible mild depression which many people experience in Seasonal Affective Disorder (SAD).
Awhile back, I posted about brain imaging studies and SAD individuals. Recently, an interesting study in the Journal of Affective Disorders looked at SAD and a possible genetic mutation in the eye, involving the gene melanopsin. Melanopsin is a photopigment in the retina which regulates circadian rhythms, hormones, and sleep.
In inidviduals who may have a melanopsin mutation, sensitivity to light is more pronounced. Therefore, more light is required to continue normal functioning during the winter months.
This study found that out of 220 individuals (130 had SAD, 90 no mental illness), 7 participants had two copies of the melanopsin mutation. All belonged to the SAD group. This gives evidence that those who carry a single copy of this genetic mutation may have a predisposition to SAD, while others who have two copies, have a strong likelihood to be afflicted with SAD.
In the end, understanding the genetics behind these illnesses can only lead to improved screening and testing which is the hope for those who may suffer.