( CNN ) -- 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 , '' 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 » . 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 predict whether or not they will be susceptible to this disease , '' Provencio said . The information may also help predict which people with seasonal affective disorder will respond to light therapy , because the mutated genes involve light sensitivity , he said . Light therapy works for some people , experts say , by mimicking outdoor light and promoting a biochemical change in the brain that improves mood . The researchers looked at 220 people , including 90 nondepressed people and 130 people diagnosed with the disorder . In this group , seven people with seasonal affective disorder had two mutated copies of the gene . The study results make sense to Dr. David Baron , chairman of Temple University 's Department of Psychiatry and Behavioral Science in Philadelphia . The study is `` consistent with the literature on understanding genetics in vulnerability to illness , '' he said . But Stephen Josephson , associate professor at Cornell University Medical Center-New York Hospital and Columbia University College of Physicians and Surgeons , said the study points to a correlation but does not constitute definitive proof . Although the specific causes of the disorder are n't known , some biological factors might contribute to it . Circadian rhythm , which helps regulate the body 's internal clock , may be disrupted with the drop in sunlight in fall and winter , MayoClinic.com says . Other research indicates that the brain chemical serotonin and the sleep-related hormone melatonin may play a role , MayoClinic.com says . Although seasonal affective disorder symptoms typically kick in around late autumn or early winter , some people experience `` summer depression , '' accompanied by symptoms such as anxiety , insomnia , irritability , agitation , and poor appetite , according to MayoClinic.com . Experts say seasonal affective disorder is more prevalent in places farther from the equator . Someone who has a genetic predisposition to SAD may not have problems if he or she lives in Singapore , for example , Baron said . Some people with seasonal affective disorder use a light box , a device that shines a bright light similar to outdoor light , which a patient sits in front of for a half hour or hour a day , Josephson said . Experts say consult a doctor if you feel you may have seasonal affective disorder . Certain cases require antidepressants or other medications , but some people manage it through light therapy or psychotherapy . For winter depression , MayoClinic.com also recommends exercising regularly and , if possible , taking vacations to warmer , sunnier places . Cootey said this winter he will try to learn how to ski and ice skate . He recommends finding a support community , such as an online forum or his blog , The Splintered Mind . He also finds relying on humor keeps spirits up . He has relied on cognitive behavioral therapy to manage depression for 16 years . With a therapist , he tries to identify what triggers the disorder or other problems . `` Change your thinking , change your life . Mind over mood . These are the mantras that keep me in control of my depression and will help me overcome , or at least manage SAD , '' he said .
Between 4 and 6 percent of the U.S. population suffers from SAD . Light therapy , psychotherapy , and medications are treatment options . Recent research indicates genetic component to the condition .