January 19, 2018 | by Betsy Brown MD, AAHIVS

Seasonal affective disorder (SAD) is a common condition that affects nearly 10 million Americans each year. SAD is related to a change in the seasons; it typically comes and goes at about the same time each year. Symptoms often start in the fall, continue through the winter months and fade away in spring. Though less common, there is also a spring-onset type of seasonal affective disorder.

SAD is a type of depression and can have similar symptoms:

  • Feelings of hopelessness or sadness
  • Fatigue
  • Irritability
  • Loss of interest in favorite activities
  • Problems with sleeping
  • Changes in appetite or weight
  • Feeling sluggish or agitated
  • Difficulty concentrating
  • Thoughts of death or suicide

SAD occurs more frequently in regions far from the equator that receive less sunlight during the day. SAD also occurs more frequently in those with a family history of other types of depression. The exact cause of seasonal affective disorder remains unknown. The reduced level of sunlight in fall and winter is thought to contribute to winter-onset SAD. This decrease in sunlight may disrupt your body's internal clock and circadian rhythm and lead to feelings of depression.

Treatment types

Treatment for seasonal affective disorder may include light therapy, medications, and psychotherapy. Light therapy, also called phototherapy, is very effective and involves sitting in front of a "light box” each day, usually first thing in the morning. The light box mimics natural daylight and is thought to change the brain chemicals linked to mood. It usually works to relieve symptoms in days to weeks with little or no side effects. It’s important to avoid using the light box later in the day because it can interfere with sleep. Several brands are available over the counter and are most effective if they have at least 10,000 LUX in brightness.


  • Make your environment as bright as possible. Turn on lights and sit near windows during the day to get exposure to as much light as possible.
  • Take advantage of sunlight. Get outside, take a walk, or simply sit on a bench and soak up the sun (or clouds). Even on gray days, outdoor light can help — especially if you spend some time outside within two hours of getting up in the morning.
  • Exercise regularly. Physical activity helps relieve stress and anxiety, both of which can increase SAD symptoms.
  • Plan fun activities in winter. Try to have a positive outlook for the winter season and plan activities you’ll look forward to and enjoy.

When to see a doctor

It's normal to feel sad on occasion. If you feel down or depressed for days at a time and you can't get motivated to do activities you normally enjoy, talk with your doctor. This is especially important if you feel hopeless, think about suicide, or turn to alcohol or drugs for comfort or relaxation.