Keywords

seasonal affective disorder, SAD, vitamin d, serotonin, sunlight, depression, anxiety, obsessive-compulsive disorder

Abstract

This literature review examines the symptoms, theorized causes, and comorbidity of seasonal affective disorder (SAD). Although causes of SAD remain unknown, researchers have observed a common pattern of vitamin D deficiency among patients with SAD. The importance of vitamin D in regulating serotonergic activity has been well documented, including the positive correlation between decreased serotonin levels and increased depressive symptoms. For more than 30 years, researchers have hypothesized that decreased serotonin activity is linked to symptoms of SAD. Furthermore, patients with other mental disorders, including depression, bipolarity, obsessive-compulsive disorder, etc. are likely to experience aggravation of symptoms during peak SAD months. Findings indicate that modifications to humans’ natural environment–dictated by modern culture–may contribute to the onset of SAD. Such modifications include spending significantly more time indoors and avoiding ultraviolet radiation. Such cultural adaptations contribute to inadequate levels of vitamin D, which increase a patient’s risk for chronic disease and mental illness, such as SAD. Health professionals and patients are encouraged to consider lifestyle adjustments in addition to other forms of treatment in alleviating symptoms of SAD.