Seasonal Affective Disorder

What is Seasonal Affective Disorder?

Seasonal Affective Disorder is a common medical condition where people experience mild to strong symptoms due to the effects of the seasonal changes no the nervous system, hormones and Vitamin D levels in the body. There are three main categories of symptoms:

  1. Cognitive - The cognitive symptoms are inability to focus and lack of attention and clarity of thoughts, forgetfulness, feeling “spacey” and poor recollection of information. People may lack spontaneity, wit or feel less smart than usual. They might find themselves staring off into space.
  2. Mood - Mood symptoms can consist of feelings of depression, anxiety, easy irritability, easy frustration, sadness, and quick fluctuations of mood. Sometimes it is difficult to understand and tolerate other people’s idiosyncrasies but SAD makes it hard to tolerate them. People can become sarcastic and cynical while others feel emotional and short tempered. The expression of this disorder varies a lot, but generally speaking, if you notice drastic differences in mood along with other related symptoms, SAD could be at play.
  3. Neuro-vegetative - These symptoms are related to change in sleep, appetite and energy. Lack of energy (anergia), disturbed sleep either broken (Insomnia) or increased need to sleep called hypersomnia, lack of zest for life (anhedonia), vegetating, hibernating, increased cravings for carbohydrate foods, generally weight gain and lack of sexual interest. The desire to engage in physical activity is low but the benefit of exercising may still be experienced. The sedentary activities increase and they are highly desired. Self-motivation and direction may plummet despite sincere attempts to regain control over life. Individuals may feel increase in their symptoms of chronic arthritic pains and fibro-myalgia. An increased susceptibility to other medical conditions such as head colds, bronchitis, diabetes, hypertension, migraine headache], low back pain, hip pains, generalized bony aches and pains and neck pains.

How does Seasonal Affective Disorder (SAD) work?

The symptoms experienced in SAD (also known as WINTER BLUES or CABIN FEVER) are due to changes in hormones/ neurochemicals in different body parts triggered by the seasonal changes. The seasonal change is experienced through out the world however population in temperate climate in the northern hemisphere is particularly vulnerable. The seasonal change due to relative positioning of the Earth to the Sun changes the duration, wavelength and the intensity of the sunlight in different parts of the world. These changes also cause physiological changes in the human body. As the sun does not rise high enough in the sky in the winter months, people who live in high latitudes require more dietary intake of vitamin D3 and D2. It has been shown that above 35º north latitude (Atlanta), little or no vitamin D3 can be produced from November to February. (2)

We humans need sunlight of appropriate wavelength and brightness to pass through our eyes to stimulate the optic nerves and related hormonal gland called Pineal gland in the brain. This system is important for maintaining normal circadian rhythm . Melatonin is the main hormone involved in the sleep-wake cycle.

Hence SAD seems to be caused by exaggerated normal response of the human body to the sunlight during the seasonal changes leading to imbalance in the functioning of the pineal gland, associated areas in the Hypothalamus and the circadian rhythm. These changes in the brain affect other bodily functions through the hormones/neurochemicals secreted in the blood stream by the hypothalamic-pituitary axis. This connection between the brain and rest of the body is the main cause for the physical symptoms seen in SAD.

Another strong possibility is changes brought on by the lack or decrease in the synthesis of vitamin D. People living in the temperate climate are particularly vulnerable to the lack of sunlight that helps in the manufacturing of the vitamin D in the skin from cholesterol. The natural process requires a very specific and narrow wavelength around 297+/-3 cm-6, and hence makes people in the northern hemisphere highly susceptible to the Vitamin D insufficiency or deficiency. Children and adolescents are at high risk for vitamin D deficiency. In studies in Boston and Maine (northern latitudes), it was found that 52% of Hispanic and black adolescents and 48% of white preadolescent girls were vitamin D deficient (less than 20 ng/mL serum 25-OHD) (1,2). 60-80% of the adult and elderly populations have low vitamin D levels.

How can I treat SAD?

Vitamin D is needed for optimal functioning of our nervous system, muscles, bones, heart, colon, and immune system. Hence vitamin D related conditions including chronic pains, fibromyalgia, and SAD improve with the correction of the vitamin D levels. In the Toronto study on winter related depression, the patients clearly improved with 600 I.U. or 4000 I.U. per day of vitamin D. They reported improved sense of wellness with 4000 I.U. per day compared with 600 I.U. per day of the vitamin proving that vitamin D seem to have antidepressant properties and works for the winter blues. (3)"

Another possible treatment for SAD is a light fixture that emits 10,000 lux of light. This treatment works the best if used daily, first thing in the morning, and for 30-45 minutes from mid August to Mid April. Generally speaking, the light therapy alone is rarely sufficient for moderate to severe SAD. Some studies prove that the mechanism through which the light therapy works is unrelated to the vitamin D therapy and hence both modes of treatments have antidepressant benefits through separate but complementary mechanisms. In clinical practice it is not uncommon to use a multimodal approach for a particular condition. Vitamin D replacement therapy can be combined with chemicals with natural antidepressant properties ( Tyrosine, SAM-E, Vitamin B complex, Methyl folate) or conventional antidepressants.


1. Rebecca Wike Malone and Cathy Kessenich. Vitamin D deficiency: implications across the lifetime, The Journal for Nurse Practitioners – JNP; June 2008; 448-454.

2. Getup H, Mikkelson K, Poulsen L, et al. Commonly recommended daily intake of vitamin D is not sufficient if sunlight exposure is limited. J Intern Med. 2000; 247:260-268.

3. Reinhold Vieth, Samantha Kimball, Amanda Hu1 and Paul G Walfish. Randomized comparison of the effects of the vitamin D3 adequate intake versus 100 mcg (4000 IU) per day on biochemical responses and the well being of patients: Nutrition Journal 2004, 3:8 ( content/3/1/8).

4. Timo Partonen, Olli Vakkuri, Christel Lamberg-Allardt, and Jouko L6nnqvist. Effects of Bright Light 25-Hydroxyvitamin D 3 on Sleepiness, Melatonin, in Winter Seasonal and Affective Disorder: BIOL PSYCHIATRY 1996; 39:865—872