What causes seasonal affective disorder (SAD)?

Dr. Jeanne Morrison, PhD
Family Practitioner

The specific cause of seasonal affective disorder (SAD) is not known but may be related to the following: hormone regulation, body temperature, and ambient light. It is also probable, like with other forms of depression, that genetics, age, and one's chemical balance play a major role in developing the disorder. One reason SAD most often occurs in the fall and winter months may be the lack of sunlight. Less light will interrupt your circadian rhythm, making it difficult for your body to know when it is supposed to be awake or asleep. An increase in melatonin, which regulates sleep, may also be the case in someone affected with SAD. On the other hand, a drop in serotonin - which regulates mood - may occur as the hours of sunlight get shorter. Each of these chemical imbalances can lead to symptoms of depression.

Although the exact mechanism is unknown, lack of exposure to adequate sunlight and imbalances of two key neurotransmitters -- serotonin and melatonin -- may be implicated in triggering the type of depression known as seasonal affective disorder (SAD). Genetic predisposition and stress also may play a role in the etiology of SAD according to Dr. Norman Rosenthal, the physician who first described seasonal patterns of depression. Treatments for SAD include phototherapy and antidepressant medication. Sufferers may notice a decrease in their symptoms by adopting healthy eating habits and adhering to a regular sleep schedule. Exercising outside may prove especially helpful for two reasons -- release of endorphins and increased exposure to sunlight.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.