Cootey said . `` Now that I know what 's going on , I 'm trying to counteract it . ' Between 4 and 6 percent of the U.S. population suffers from seasonal affective disorder , according to the Cleveland Clinic in Ohio , but 10 to 20 percent of the population may suffer from more mild winter doldrums . SAD is more common in women in their 20s , 30s , and 40s , the Cleveland Clinic says . Some people may be genetically predisposed to SAD , but the environment can trigger it as well , said Ignacio Provencio , a biology professor at the University of Virginia . Learn about other mood disorders Â '' A recent study led by Provencio shows that a genetic mutation in the eye could play a role in seasonal affective disorder . The mutation makes a person with SAD less sensitive to light . The photopigment gene is called melanopsin , which helps detect colors . `` Being able to look at one 's DNA and seeing that you 're a carrier or contain two copies of this gene may be able to , in the future , allow one to
-LRB- CNN -RRB- -- Douglas Cootey is replacing his lightbulbs with brighter ones , but not just to see better . The new broad spectrum lights simulate sunlight , and might help enliven his mood in the gloomy winter months . A light box like the one shown here may help some people combat seasonal depression in winter . Cootey , a stay-at-home dad in Salt Lake City , Utah , has struggled with depression for 16 years and shares his story with others on his blog , The Splintered Mind . He said he started to notice last year that his depression was harder to manage in the winter . His challenge , he told CNN , is `` keeping a positive and upbeat attitude in the face of a chemical onslaught induced by winter . '' He realized that his symptoms fit those of seasonal affective disorder , a condition that typically generates depression during autumn and winter and then goes away in the sunnier months . In rarer cases , people can suffer from it only in summer . `` I set the clock back and look at this : I 've been so unproductive , ''