What is seasonal affective disorder (SAD)?

Seasonal affective disorder (SAD) is a type of depression associated with changes in the seasons. SAD can be categorized as either “winter type” or “summer type.” Winter type SAD is more common, with symptoms beginning during autumn or winter. 1%-10% of adults (mostly women) experience SAD and display symptoms of decreased energy and moodiness.

What are the symptoms?

  • Symptoms of SAD include:
    • Depressed mood
    • Losing interest in activities you usually enjoy
    • Having low energy
    • Sleep changes
    • Weight gain; craving sweets
    • Feeling hopeless
    • Having suicidal thoughts
  • “Winter type” symptoms:
    • Oversleeping
    • Weight gain; craving sweets
    • Low energy
  • “Summer type” symptoms:
    • Trouble sleeping
    • Poor appetite; weight loss
    • Anxiety
    • Increased irritability

What are some causes and risk factors SAD?

The exact cause of SAD is not known. Possible causes include:

  1. Circadian rhythm (your biologic clock)
    • Your biologic clock may be interrupted due to the seasonal changes in daylight. Decreased sunlight has been associated with feelings of depression.
  2. Decreased serotonin levels
    • Serotonin is a chemical that helps manage your mood. A lack of sunlight may be affecting your serotonin levels, which may lead to depression.
  3. Decreased melatonin levels
    • Changes in the season may disrupt your melatonin levels, which may be responsible for sleep changes.

Risk factors:

  • Living farther north of the equator
  • Working night shifts
  • Family history of mood disorders
  • Having a major depressive disorder
  • Having low levels of vitamin D

How is SAD diagnosed?

If you think you might be experiencing SAD, you can talk to your doctor or a mental health specialist about your symptoms. They will be able to assess you to see if your symptoms meet the criteria for SAD.

Criteria for SAD diagnosis include:

  • Symptoms of major depression (i.e., feelings of emptiness, worthlessness, or anxiety, troubles sleeping, or loss of interest in most/all normal activities) or the more specific symptoms listed above.
  • Depressive episodes occurring during specific seasons for at least 2 years in a row.
  • If you had other episodes of depression, the seasonal episodes must happen more often than the other depressive episodes you may have had throughout the year

Treatment of SAD

There are effective treatment options for SAD that can be used alone or in combination. Be sure to talk to your doctor to see which treatment option(s) is(/are) best for you.

  1. Light therapy
    • First-line treatment option
    • Sit a few feet from a special light box so that you’re exposed to bright light within the first hour of waking up each day. The light will mimic natural outdoor light to make up for the lack of light experienced during the winter months.
  2. Psychotherapy/cognitive behavioral therapy
    • Teaches you how to cope with SAD, manage stress, and increase healthy behaviors
  3. Medications
    • Antidepressants
      • Bupropion
      • Selective serotonin reuptake inhibitors (SSRIs), such as 
        • Fluoxetine (Prozac®)
        • Citalopram (Celexa®)
        • Sertraline (Zoloft®)
        • Paroxetine (Paxil®)
        • Escitalopram (Lexapro®)
    • Talk with your doctor to see if starting a medication is the best treatment option for you. All medications have side effects, so it is good to understand the possible risks of using medications for your condition.
  4. Activity
    • Consider spending some time outdoors. Open windows or go for walks to expose yourself to more sunlight. Exercising is also a great way to increase serotonin levels to help maintain a good mood. Maintaining good sleep hygiene can also prevent changes in your melatonin levels.


Galima, S. V., Vogel, S. R., & Kowalski, A. W. (2020, December 1). Seasonal affective disorder: Common questions and answers. American Family Physician. Retrieved November 28, 2022, from https://www.aafp.org/pubs/afp/issues/2020/1201/p668.html

Mayo Clinic. (2021, December 14). Seasonal affective disorder (SAD). Mayo Clinic. Retrieved November 28, 2022, from https://www.mayoclinic.org/diseases-conditions/seasonal-affective-disorder/diagnosis-treatment/drc-20364722

National Institute of Mental Health. (n.d.). Seasonal affective disorder. National Institute of Mental Health. Retrieved November 28, 2022, from https://www.nimh.nih.gov/health/publications/seasonal-affective-disorder#part_6696

Written by:

Miranda Barker
PharmD Candidate 2025
Philadelphia College of Pharmacy