Seasonal affective disorder (SAD) is a subtype of depression that comes and goes with the changes in seasons. The “winter blues” typically begins in the late fall and early winter and ends around late spring. Depressive episodes linked to the summer can occur but are much less common than winter episodes of SAD. Individuals must meet the criteria for major depressive disorder coinciding with specific seasons, and symptoms must be present for at least two years.

Melatonin and serotonin

The reduced level of sunlight in the fall and winter months may affect an individual’s serotonin and melatonin levels. Serotonin is a neurotransmitter that affects mood. Medications that increase the level of serotonin in the brain are first-line treatment agents for depression. Brain images have shown that individuals who had seasonal depression in the winter had higher levels of a serotonin transporter protein. This protein is responsible for removing serotonin in the brain.

Melatonin, a sleep-related hormone secreted by the pineal gland in the brain affects sleep patterns and mood. Melatonin is produced at higher levels in the dark and therefore melatonin is increased when the days are shorter and darker. An increase in melatonin induces sleep and regulates an individual’s circadian rhythm.

Signs and symptoms of SAD

  • Daily depression
  • Losing interest in activities and hobbies
  • Having low energy
  • Having difficulty sleeping
  • Experiencing changes in weight and appetite
  • Feeling fatigued
  • Feeling agitated
  • Having difficulty concentrating
  • Feeling hopeless, worthless or guilty
  • Having frequent thoughts of death or suicide

Risk factors associated with seasonal affective disorder

Interestingly enough, certain factors increase the risk of developing seasonal affective disorder.

  • Female gender: Females are four times more likely to be diagnosed with SAD compared to men
  • The location from the equator: Individuals who live far north or south of the equator are more likely to develop seasonal affective disorder. One percent of individuals who live in Florida have SAD whereas nine percent of individuals who live in Alaska have SAD.
  • Positive family history: Like with many other mental health disorders, individuals who have a family history of depression are at risk for developing seasonal affective disorder.
  • Personal history of bipolar disorder or depression: SAD is considered a mood disorder. Individuals who have had a previous mood disorder such as depression or bipolar disorder are at an increased risk for developing SAD.
  • Younger age: Research has shown that younger adults are more at risk of developing SAD compared to older adults.

Seasonal affective disorder treatment

The mainstay treatment for seasonal affective disorder is light therapy; however, other treatment options are available. Alternative treatment options include antidepressants specifically, cognitive behavioral therapy and dialectical behavioral therapy. Exercise, a well-balanced diet, a positive social group, and self-care are all important lifestyle changes that can help improve seasonal affective disorder.

Light therapy and seasonal affective disorder 

A light therapy box has similar characteristics to natural outdoor light. Researchers believe this type of light causes a chemical change in the brain that improves mood and helps with symptoms of SAD. There are specific lightboxes that are used to treat SAD, while many others are used to treat specific skin conditions. The main difference between these two types of boxes is that lightboxes for SAD filters out UV light. Lightboxes for skin disorders use UV light to help treat skin disorders. Lightboxes for SAD can be purchased without a prescription and come in different shapes and sizes; some resemble lamps while others resemble rectangular boxes. They average $75, and bulbs should be replaced every 2-3 years, as most lightboxes use LED bulbs.


Kristen Fuller, M.D., is a clinical content writer and enjoys writing about evidence-based topics in the cutting-edge world of mental health and addiction medicine. She is a family medicine physician and author, who also teaches and contributes to medicine board education. Her passion lies within educating the public on preventable diseases, including mental health disorders and the stigma associated with them. She is also an outdoor activist and spends most of her free time empowering other women to get outside into the backcountry.