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Seasonal Affective Disorder (SAD): Causes, Symptoms, Diagnosis & Treatment

Last Updated on Jul 25, 2013
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Seasonal Affective Disorder is a type of clinical depression that is triggered only at a particular time of the year; it occurs and remits with changes in seasons.


Seasonal Affective Disorder (SAD) is a type of clinical depression that follows a seasonal pattern. Two seasonal patterns have been identified as being associated with SAD. The most common SAD is “Winter Blues” that occurs in winter. Individuals start to build up symptoms from late autumn and continue through the winter months. The summer depression or “Reverse SAD” results in a severe depressive episode that begins during late spring and continues through the summer months.

Seasonal Affective Disorder (SAD) | Winter Depression | Winter Blues

Causes and Risk Factors of Seasonal Affective Disorder

The exact cause of SAD is unknown. However, it is believed to be due to a biochemical imbalance in the brain resulting in altered sleep-wake cycle or circadian rhythm. The suggested causes of SAD include:

  • Increased melatonin synthesis: Melatonin is a hormone that aids in sleep. It is secreted more at night. Its secretion is inhibited by sunlight. During winter, since the days are shorter, more melatonin is produced. Altered melatonin levels could affect a person’s mood and result in SAD.
  • Circadian Phase Shift : As the season changes, people experience circadian rhythm shift due to the changes in the length of the day and night, and that directly affects mood.
  • Decreased serotonin levels : Serotonin is a neurotransmitter responsible for satisfied, happy and cheerful feeling. Studies reveal that serotonin levels are high during day time. Hence, most people feel happy, energetic and enthusiastic during sunny days. In winters, reduced serotonin levels may result in symptoms of depression.

Those at a higher risk for SAD include-

  • Female sex
Causes and Risk Factors of Seasonal Affective Disorder: Female Sex
  • Individuals with family members or close relatives with SAD or any other type of depressive disorder
  • People living in the higher altitudes away from the equator
  • People with low vitamin D blood levels
  • Individuals with reduced retinal sensitivity to light, endocrinal disorders and certain personality traits

Signs and Symptoms of Seasonal Affective Disorder

Symptoms associated with SAD include-

  • Feeling of gloom, guilt and loss of self esteem
  • Lack of energy and feeling of fatigue that disturb daily routine
  • Irritability and stress
  • Difficulty in concentration
  • Over sleep or Lack of sleep
Signs and Symptoms of Seasonal Affective Disorder: Over Sleep or Lack of Sleep
  • Lack of interest in social activities
  • Over eating and sudden weight gain
Signs and Symptoms of Seasonal Affective Disorder: Over Eating
  • Carbohydrate craving
  • Anxiousness without any apparent cause
  • Loss of libido
  • Sudden mood swings during winter
Signs and Symptoms of Seasonal Affective Disorder: Mood Swings

SAD symptoms abate as the days lengthen i.e. during spring and usually disappear completely during summer.

Symptoms associated with Summer Depression include-

  • Poor appetite
Signs and Symptoms of Seasonal Affective Disorder: Poor Appetite
  • Weight loss
  • Lack of sleep
  • Irritability
  • Crying spells
Signs and Symptoms of Seasonal Affective Disorder: Crying Spells
  • Anxiety or agitation

Patients with bipolar disorder may suffer from symptoms like hyperactivity, elevated mood and rapid thoughts and speech.


Diagnosis of Seasonal Affective Disorder

Diagnosis of SAD is based on-

  • Patient History
  • Physical examination
  • Seasonal Assessment Questionnaire (SAQ), which helps to determine sleep patterns, weight changes, mood changes, energy levels and social activities
Diagnosis of Seasonal Affective Disorder: Seasonal Assessment Questionnaire (SAQ)

Treatment of Seasonal Affective Disorder

Once diagnosed, SAD should be promptly treated; or else may develop long-term depression or bipolar disorder. Treatment includes:

Light therapy

Light therapy is considered as first-line treatment to treat SAD. In such treatments, the person is exposed to a very bright light that mimics the light from sunrays. It works best when started in the early winters, before the symptoms of SAD begin. Side-effects include eye strain, hypomania, photophobia, irritability and headache. It is necessary to consult a doctor before starting this therapy especially if the individual has an eye problem or has been taking antidepressants or medications to treat epilepsy.

Light therapy has been used in combination with other therapies, including cognitive-behavioral therapy, L-tryptophan, and St.John’s wort.


Antidepressants are safe and effective medications for treating SAD.

Treatment of Seasonal Affective Disorder: Antidepressants
  • Serotonergic antidepressants are mostly preferable for this purpose.
  • The antidepressant agomelatine has also found to be promising, though it is not available in all countries.
  • Tryptophan has shown to benefit non-responders to light therapy.
  • St.John’s wort (Hypericum perforatum) has been used to treat mild-to-moderate depression. St.John’s wort interacts adversely with many prescription drugs. Hence, it is necessary to consult your doctor before starting with St.John’s wort.

Antidepressants can be used with or without light therapy.

Cognitive-Behavioral Therapy

Counseling and cognitive–behavioral therapy helps to identify and change negative thoughts and behavior. Also, it helps the individual to learn ways to cope with seasonal affective disorder and manage stress.

Treatment of Seasonal Affective Disorder: Cognitive Behavioral Therapy

Measures for coping with SAD include-

  • Allow more natural sunlight into your day by spending time outdoors, going for a long walk on sunny days and keeping the curtains or blinds open. Decorate your rooms with bright and cheerful colors.
  • Eat a well-balanced diet. Omega-3-fatty acid supplements may help to relieve SAD symptoms to some extent.
Treatment of Seasonal Affective Disorder: Omega-3 Fatty Acid
  • Talk to people and share your feelings with those who are caring and positive.
  • Regular exercise relieves stress and anxiety that seems to be more during SAD and helps to feel better.
Treatment of Seasonal Affective Disorder: Regular Exercise
  • Improve your sleep patterns and get enough sleep.
  • Go to a sunny destination during winter if possible.
  • Avoid alcohol and illegal drugs.
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  1. Miller AL. Epidemiology, Etiology, and Natural Treatment of Seasonal Affective Disorder. Altern Med Rev 2005; 10(1):5-13.
  2. Seasonal affective disorder (SAD) - (http://www.mayoclinic.com/health/seasonal-affective-disorder/DS00195/DSECTION=tests-and-diagnosis)

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