Melatonin is the hormone thought to communicate signals from the body s internal clock. While 90 percent of the body s melatonin is produced by the pineal gland, the remainder is manufactured by specialized cells in the retina. Park said melatonin s main function is to increase sleepiness. More melatonin is present in the body during the short, gray days of winter, and research indicates that people who suffer from SAD release melatonin later into the morning than other people, making it harder for them to wake up in the morning. Most sufferers report feeling better within two weeks after starting light therapy.
Light therapy works for many people, but can lead to eyestrain, headaches, insomnia or irritability.
Light therapy is not advised for people with retinal problems, whose skin is hypersensitive to light, or anyone taking medications that heightens light sensitivity. Taking a daily walk outdoors is an alternative to costly light therapy. However, check with your doctor if you suffer from depression throughout the year and it gets worse during the fall and winter months.