On November 14, 2008, the Charlottesville, VA newspaper, Daily Progress, reported on a recent study conducted by Iggy Provencio of the University of Virginia. That study suggests that some who suffer from Seasonal Affective Disorder (SAD) may have a genetic predisposition to the malady.
In the study, 220 people were tested. Of the 220, 130 were diagnosed as having SAD. Also of the 220, 7 of them were found to have two mutated copies of a gene that directly affects the photopigment in the eye called melanopsin*. While a number of people were found to have only one mutated copy of the gene, all 7 of those with the double mutation were among the 130 diagnosed with SAD.
Exactly what this means, or how it will help, is yet to be determined. Standard treatment for people with SAD is bright light treatment with full spectrum lights, but this treatment is purportedly only effective in about half of all cases, which leaves a large portion of those affected without an effective treament. Study into the genetic aspect may help bring about more information on how to more thoroughly treat this disorder.
*Melanopsin is a photopigment found in our eyes that is, by design, reactive to light, whether as part of or when removed from the body. This makes is a Photorecptor. For those of us who graduated from high school before 2002 (melanopsin was first discovered in 1998), we may remember the other two types of photoreceptors in the eye, the rods and cones. Melanopsin joines them as a newly discovered 3rd.
Unlike the cones and rods, however, melanopsin does not seem to be related to the processing of images or motion. Rather, it seems intrinsically linked to automatic and reflexive responses within our bodies. Among these processes, melanopsin seems to be linked to our body’s circadian rhythms. Our circadian rhythms are what tells us when its time to sleep and wake up. They dictate our daily ‘flow’, of which daylight is a major influence.
Melanopsin was originally discovered in the skin of frogs by Ignacio Provencio and his colleagues in 1998. In 2000, Provencio showed that humans and other mammals also produce Melanopsin, and that for us, it is only found in our retinas.