Understanding Seasonal Affective Disorder

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Seasonal Affective Disorder (SAD) is a type of depression that occurs at specific times of the year, most commonly in fall and winter. It is linked to reduced sunlight exposure and is sometimes referred to as "winter depression."

Symptoms of SAD

  1. Emotional:

  • Persistent sadness or depressed mood.

  • Feelings of hopelessness or worthlessness.

  • Irritability or anxiety.

  1. Behavioural:

  • Low energy or fatigue.

  • Loss of interest in activities once enjoyed.

  • Difficulty concentrating.

  1. Physical:

  • Changes in sleep patterns (oversleeping or insomnia).

  • Changes in appetite (craving carbohydrates or overeating).

  • Weight gain (commonly associated with winter SAD).


Risk Factors for SAD


  1. Geographic location:

  • More common in regions farther from the equator, where there is less winter daylight.

  1. Biological sex:

  • Women are more likely to experience SAD than men.

  1. Age:

  • Younger adults are more at risk, but it can occur at any age.

  1. Family history:

  • A family history of SAD or other forms of depression increases risk.

  1. Pre-existing mental health conditions: 

  • Those with major depressive disorder or bipolar disorder may be more prone to seasonal variations.

  1. Occupation:

  • Shift workers may be at particular risk.


Mechanisms behind SAD


  1. Circadian rhythm disruption:

Reduced sunlight exposure can disrupt the body’s internal clock, affecting sleep and mood.

  1. Melatonin dysregulation:

Increased melatonin production due to longer nights can cause excessive sleepiness and fatigue.

  1. Serotonin deficiency:

Reduced sunlight can lower serotonin levels, leading to depressive symptoms.

  1. Vitamin D deficiency:

Lack of sunlight decreases vitamin D synthesis, which may play a role in mood regulation.


Management of SAD


1. Light Therapy

  • Bright Light Therapy (BLT):
    Use a lightbox emitting 10,000 lux for 30 minutes daily, ideally in the morning. Helps regulate melatonin production and support serotonin levels.

2. Psychotherapy

  • Cognitive behavioural therapy (CBT):
    CBT tailored to SAD helps individuals manage negative thoughts and establish healthier routines.

3. Medication

  • Antidepressant medications can be prescribed by a medical professional.

5. Vitamin D supplementation

  • Low vitamin D can contribute to depression. Many people with SAD have insufficient or deficient levels of Vitamin D. 


Dietary and Nutrient Recommendations


Increase Omega-3 fatty acids:

Found in fatty fish (salmon, mackerel), flaxseeds, walnuts, and chia seeds. Support brain health and mood regulation. Omega-3 fatty acids (EPA and DHA) supplements may support mood regulation.

Include complex carbohydrates:

Whole grains, legumes, and vegetables to stabilise blood sugar and energy levels.

Have vitamin D-rich foods:

Fatty fish, egg yolks, fortified dairy products, and plant-based milks. Vitamin D supplement may also be helpful especially in case of low status. 

Magnesium-rich foods:

Nuts, seeds, spinach, and avocados, as magnesium is linked to improved mood and sleep. Magnesium glycinate can support sleep and relaxation.

Antioxidant-rich Foods:

Berries, dark leafy greens, and colourful vegetables help to combat oxidative stress.


Lifestyle modifications


Outdoor exposure:

Spend time outside daily, especially in the morning, even on cloudy days. Engage in outdoor physical activities like walking or hiking.

Regular exercise:

Moderate-intensity aerobic exercise (like jogging or yoga) may support serotonin levels.

Consistent sleep schedule:

Maintain regular wake-up and bedtimes to support circadian rhythm.

Stress management:

Practice mindfulness, meditation, or breathing exercises to reduce anxiety.

Social interaction:

Stay connected with friends and family to combat feelings of isolation.


Summary of an Integrated Approach

  • Combine light therapy, a nutrient-rich diet, regular exercise, and social engagement.

  • Use supplements like Vitamin D and omega-3s as needed.

  • Seek professional help if symptoms are severe, incorporating CBT or medications when necessary.




  1. Melrose S. Seasonal Affective Disorder: An Overview of Assessment and Treatment Approaches. Depress Res Treat. 2015;2015:178564. doi: 10.1155/2015/178564. Epub 2015 Nov 25. PMID: 26688752; PMCID: PMC4673349.

  2. Munir S, Gunturu S, Abbas M. Seasonal Affective Disorder. [Updated 2024 Apr 20]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK568745/