"Jan Brehm lives in rainy Portland Ore. and she has always dreaded this time of year when the days get shorter her mood plummets and all she wants to do is crawl into bed and eat cookie dough. She and her husband were considering moving to Arizona or Colorado  anywhere with more sunlight  until last year when she purchased her first artificial light box. She keeps it on her desk and every morning before she starts her workday she turns it on and basks in the bright artificial light for about  to  minutes while catching up on her reading. The boxes come in different sizes Ms. Brehms is about  inches high and  inches wide and she keeps it a foot or more from her face. I still say to myself Its a dark crummy day when the clouds roll in Ms. Brehm a yearold actress and entrepreneur said. The difference is I dont feel like going back to bed. For the millions of Americans who suffer from mild to severe winter blues  a condition called seasonal affective disorder httphealth.nytimes.comhealthguidesdiseaseseasonalaffectivedisorderoverview.htmlinlinenytclassifier or S.A.D.  brightlight therapy is the treatment of choice with response rates comparable with those of antidepressants httptopics.nytimes.comtopnewshealthdiseasesconditionsandhealthtopicsantidepressantsindex.htmlinlinenytclassifier. Your natural clock is usually longer than  hours and you need light in the morning to set it and keep it on track said Dr. Alfred Lewy a professor of psychiatry httptopics.nytimes.comtopnewshealthdiseasesconditionsandhealthtopicspsychiatry_and_psychiatristsindex.htmlinlinenytclassifier at Oregon Health and Science University and an expert on seasonal depression httphealth.nytimes.comhealthguidessymptomsdepressionoverview.htmlinlinenytclassifier and light therapy. Yet many experts think light therapy is underused given its affordability and relative lack of side effects in large part because there is little profit to be made from it and no commercial incentive to promote the treatment. Patients generally sit in front of the light box which can be as small as  by  inches and  inches deep with the bright light emanating from the square surface in the morning. With the natural dawn being later in winter the body rhythms drift late Dr. Lewy said. If you can fix the drift you can fix the depression. Light therapy may even help with major nonseasonal depression experts say and with sleep disorders httphealth.nytimes.comhealthguidesdiseasesleepdisordersoverview.htmlinlinenytclassifier. And because it has few side effects researchers are studying whether light therapy can help with depression during pregnancy httptopics.nytimes.comtopnewshealthdiseasesconditionsandhealthtopicspregnancyindex.htmlinlinenytclassifier and be used to treat elderly people with dementia httphealth.nytimes.comhealthguidesdiseasedementiaoverview.htmlinlinenytclassifier. It is also being investigated for the treatment of bulimia nervosa httphealth.nytimes.comhealthguidesdiseasebulimiaoverview.htmlinlinenytclassifier severe premenstrual syndrome httphealth.nytimes.comhealthguidesdiseasepremenstrualsyndromeoverview.htmlinlinenytclassifier and even attention deficit hyperactivity disorder httphealth.nytimes.comhealthguidesdiseaseattentiondeficithyperactivitydisorderadhdoverview.htmlinlinenytclassifier and bipolar disorder httphealth.nytimes.comhealthguidesdiseasebipolardisorderoverview.htmlinlinenytclassifier. Though randomized controlled clinical trials of bright light are difficult to do properly  one expert is fond of saying that it is difficult to blind studies of bright light  the American Psychiatric Association considers brightlight therapy an effective lowrisk treatment for both S.A.D. and nonseasonal major depressive disorder httphealth.nytimes.comhealthguidesdiseasemajordepressionoverview.htmlinlinenytclassifier. A  multicenter doubleblind randomized controlled trial that compared brightlight therapy head to head with the popular antidepressant Prozac httptopics.nytimes.comtopnewshealthdiseasesconditionsandhealthtopicsprozac_drugindex.htmlinlinenytclassifier fluoxetine in  subjects found the two treatments equally effective for alleviating winter depression http though light produced results faster usually within a week and with fewer side effects. Why then do so few doctors prescribe brightlight therapy Some say their patients dont have the patience to sit in front of a light for  to  minutes every morning. Moreover doctors are just more comfortable prescribing medication because thats what they do for everything Dr. Lewy said. Some patients who suffer from chronic depression httphealth.nytimes.comhealthguidesdiseasedysthymiaoverview.htmlinlinenytclassifier say they use light therapy in addition to their regular medication in the winter months. Ive always seen a drastic change in my personality from spring and summer to fall and winter and it got worse as I got older said Rick Bach  a painter who owns a hair salon in West Hartford Conn. and tries to spend every January in Puerto Rico. But while brightlight treatment is helpful he said it is not sufficient for him. It can help you from falling into a deep depression but it wont help you climb out of one he said. Get the best of Well with the latest on health fitness and nutrition delivered to your inbox every week. Top of Form Bottom of Form Top of Form No one knows exactly how light treatment works but most experts seem to agree that the body has a master biological clock that responds to or is set by natural light fluctuations. Light does more than just enable us to see said Dr. Norman Rosenthal author of the landmark book Winter Blues who was among the first to identify and describe S.A.D. Light also has an effect on hormones the bodys chemical messengers affecting the brains hypothalamus which is involved in regulating mood energy and appetite. The hormone melatonin which is secreted at night can be suppressed by light Dr. Rosenthal said. Studies have also shown that light influences serotonin and epinephrine httphealth.nytimes.comhealthguidestestcatecholaminesbloodoverview.htmlinlinenytclassifier pathways in the brain the same neurotransmitter systems known to be affected in people with general depression. But while part of the appeal of light therapy is that it can be selfprescribed using a light box is not as simple as it may appear. Experts recommend consulting with a knowledgeable health care provider before starting treatment to rule out other medical conditions and to help with monitoring and adjusting brightlight exposure. Some patients may want to try simply getting more natural light to help with seasonal mood changes httphealth.nytimes.comhealthguidessymptomsdepressionoverview.htmlinlinenytclassifier  getting out as much as possible during the brightest time of day in the winter sitting near windows during the day or taking vacations to sunny locales in the winter. If you choose to try light therapy here are a few tips from experts. COSTS Light boxes can be purchased for about  online they are also available for rent. Some patients manage to get insurance reimbursement by having a doctor write a letter but dont count on your policy covering it. PRECAUTIONS Side effects include headaches and hypomania though experts say these are rare. Face the light but do not stare at the light. If you have an eye condition of any kind clear light therapy with your ophthalmologist first. MORE INFORMATION Check the Web sites of the Society for Light Therapy and Biological Rhythms at  http and Center for Environmental Therapeutics at  http"