Seasonal Affective Disorder

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By Catherine Wachira, PMHNP

Seasonal affective disorder (SAD) is a form of depression that is often characterized by depressive episodes that begin in the fall or winter and remit in the spring. This is because there is less daylight during the fall and winter months, especially in places that are far from the
equator such as Alaska. Changes in season can influence a person’s serotonin and melatonin and in turn cause SAD. People with SAD have difficulty regulating serotonin, the neurotransmitter responsible for balancing mood. In addition, SAD may also cause an
overproduction in melatonin causing excessive sleep and fatigue. Keep in mind, SAD may co-occur with other disorders such as bipolar disorder, major depressive disorder, and ADHD (S. Moore, 2018).

SAD causes persistent feelings of sadness and depression, low energy, irritability, crying spells, and weight gain. One may feel extremely tired and sleep more than usual. There are several ways of treating SAD. One method that has been used for over 30 years is bright light
therapy (BLT). BLT just 30 minutes a day has been proven to be effective. Patients are positioned 12 to 18 inches away from a light box that emits a broad-spectrum ultraviolet light mimicking outdoor light. Combining the use of BLT with antidepressants has the best outcomes
compared to the use of only BLT or only antidepressants (National Institute of Health, 2017).

Selective serotonin reuptake inhibitors (SSRI’s) and cognitive behavioral therapy (CBT) have also proven to be very effective for prevention and treatment of SAD. Furthermore, taking vitamin D before winter darkness sets in may help prevent symptoms of SAD (S. Moore, 2018). Studies have shown that low levels of vitamin D are associated with depression so not surprisingly, many people with SAD have insufficient levels of vitamin D. Finally, practicing self-care throughout the year can reduce the risk of SAD as well as promote overall wellbeing. Simple self-care measures such as getting 7-8 hours of sleep per night as well as exercising regularly can be quite helpful.

In summary, sunlight plays a critical role in the decreased serotonin activity, increased melatonin production, and disrupted sleep patterns. SAD can be treated by the use of BLT, antidepressants, vitamin D supplements, and CBT. Discussing with your healthcare provider
regarding prevention and treatment of SAD is the first step toward successfully managing symptoms.


Campbell, P. D., Miller, A. M., & Woesner, M. E. (2017). Bright Light Therapy: Seasonal Affective
Disorder and Beyond. The Einstein Journal of Biology and Medicine : EJBM, 32, E13–E25.
Sherri, A. Seasonal Affective Disorder: An Overview of Assessment and Treatment Approaches.
Depression Research and Treatment. Vol. 2015, Article ID 178564, 6 pages, 2015.