Seasonal Affective Disorder

Seasonal Affective Disorder

Seasonal Affective Disorder or SAD for short is not just a pseudoscientific way for saying you don’t like the winter. It is a recognized mental illness characterized by recurring episodes of depression during fall and winter months. The prevalence of SAD over all is about 5%. The incidence increases in distance from the equator to approximately 10% in more northern latitudes where risk factors are increased (longer, more severe winters and less daylight hours in winter). One study carried out in New York City showed up to 25% of the population were suffering from the condition. The prevalence in women Vs men is about 4:1 during childbearing years. In later life this evens out and it affects older people equally in both sexes. As with almost any mental illness SAD can also affect children. January and February have been shown to be the most difficult months for patients suffering with this condition.

SAD presents with similar symptoms to other forms of depression however this form is seasonal in nature occurring primarily during the fall and winter months. Common symptoms include sadness, anxiety, irritability, premenstrual difficulties, decreased energy, activity and libido. In order to receive a diagnosis of seasonal affective disorder a person must fall under the following diagnostic criteria as outlined in the DSM-V which is the American Psychiatric Association’s diagnostic manual containing criteria for all mental disorders.

  • A regular recurrence of a major depressive episode at a particular time of year
  • Full remission or a change from major depression to mania or hypomania must also occur at particular time of year.
  • To demonstrate the seasonal relationship two major depressive episodes must have occurred in the past two years.
  • Nonseasonal major depressive episodes must not have occurred during the same period of time.
  • Seasonally related depressive episode must outnumber non seasonal major depressive episodes that may have occurred over a person’s lifetime.

Another symptom that often appears in cases of seasonal affective disorder is increased food intake (particularly craving for carbohydrates) and resulting weight gain as well as hypersomnia (increased sleeping) and reduced social and professional function.  It is important to rule out other illnesses before making a diagnosis of seasonal affective disorders. Other illnesses with similar presentation include -chronic fatigue, hypothyroidism, depression and mood disorders, bipolar and premenstrual dysphoric disorder.

SAD is a complex disorder resulting from multiple factors. Theories abound on the exact causes for this disorder but what the research does show is a clear link between reduced sunlight and seasonal depression. Disruption to the body’s circadian rhythm (body clock) caused by inadequate light exposure may be exacerbated in some people by genetic factors. Retinal sensitivity to light, neurotransmitter dysfunction and changes to brain chemistry in winter months. Other risk factors include susceptibility to stress, predisposition to depression e.g. family history and as previously mentioned, older age. It is also arguable that in winter months there is less social interaction and stimulation as people are confined indoors leading to more increasing feelings of boredom, loneliness and ultimately depression. There is an interesting link here to depression in older people. Depression has long been seen as a common, unavoidable symptom of old age for some people. As people age they are more at risk of becoming confined indoors (without sunlight) due to poor mobility, poor health or institutionalization. This can also lead them to become socially isolated. It seems there are at least some risk factors which are the same for depression in older people as seasonal affective disorder.

There are several treatments which have been shown to be effective in treating SAD. These include pharmacotherapy (medication), cognitive behavioural therapy and light therapy. Pharmacotherapy involves the use of SSRI drugs such as fluoxetine. Fluoxetine is a widely used medication. You may know it by it’s brand name Prozac. It has been shown to be useful in treating a number of different disorders including SAD, depression, anxiety disorders, OCD and eating disorders. This drug does come with side effects. In some cases it can make depressive symptoms worse. Anxiety, fatigue, nausea,  drowsiness, trouble sleeping, seizures, fainting and skin reactions are some of the potential side effects you will find on the warning label. Side effects may be one reason why up to 30% of patients who commence treatment on SSRI drugs discontinue use within 6 weeks. While not all patients may suffer these effects, studies have shown comparable result for the treatment of SAD between pharmacotherapy and light therapy. In fact, light therapy patients showed a faster response with less adverse effects then patients using medication to guide their treatment.

What is Light Therapy?

This simple non-pharmacologic intervention involves the administration of artificial light usually in the patient’s home. Recommendations vary from 2500-lux intensity to 10,000-lux and length of exposure has also been examined from 30 mins – 6 hours. Patents have seen improvements with just 30 minute treatments at a higher intensity light but most studies recommend 2 hours. Treatment is most effective when carried out once a day in the early morning. The use of different types of light have produced varying results. The most effective being full spectrum fluorescent light at a distance of 1 meter at eye level. This mimics the kind of light seen outdoors. Patients do not have to look directly at the light and they can be doing other things while receiving the treatment. They must have their eyes open and be awake for treatment to be effective. The positive anti-depressant effects of this intervention are often seen within 3-4 days and there is statistically measurable improvement within 1-2 weeks. Many patients experience a full relief of symptoms with light therapy. Some studies have shown that the beneficial effects can continue for weeks after treatment but many patients will relapse without therapy during the winter months and it is advised that they continue to receive light therapy throughout winter. It may also be beneficial to commence treatment in the early fall before the onset of winter to preempt the depressive symptoms.

The mechanism of action for light therapy is poorly understood for several reasons. It is difficult to carry out a controlled study as there is not placebo that researchers can use instead of light. Also many of the existing studies have small sample sizes and results don’t corroborate one another. This has made it difficult for researchers to gain an insight into how light therapy works why some people experience seasonal depression while others don’t. What the studies are in agreements about is the positive anti-depressant effects of light therapy with fewer side effects than medication.

One other way you can help your body to overcome seasonal depression is with what you put in it. Omega-3 fatty acids found in fish plays a huge role in the health of the nervous system and brain health. There is a growing body of evidence to support the idea that the increasing incidence of depression is linked to the decreasing amount of omega-3 in our diet. Several studies in different parts of the world have identified a link between high intake of fish which is rich in omega-3 and lower incidence of different forms of depression. Another important nutrient in terms of mental heath is vitamin D. Vitamin D is involved in brain development and maintenance.  Several studies have shown a link between low levels of vitamin D and a higher incidence of all kinds of depression including SAD. It binds to receptors in the hippocampus and cingulate which are parts of the brain known to be involved in the pathophysiology of depression. This would support the theory that vitamin D may be associated with depression and could have a role in it’s treatment. Much of our vitamin D comes from sunlight so this is particularly relevant in the case of seasonal affective disorder. Similarly, magnesium has been shown to be effective as an adjunctive therapy for depression and multiple studies show that people with an increased intake of magnesium are less likely to have depression. What much of the research does stress is the need for more controlled trials and research into the use of these simple and cost effective therapies for depression.

If you feel that you may be experiencing depression, seasonal or otherwise, talking to your naturopathic doctor might be helpful. Naturopathic doctors can bring together a wide range of tools and knowledge including nutritional guidance, supplementation, botanical and herbal medicine,  counselling, acupuncture and pharmacologic interventions to create a tailored plan for you. The practitioners at Yaletown Naturopathic Clinic are experienced in offering effective support to optimize your mental and physical wellbeing. 


1.Bright Light Treatment Decreases Depression in Institutionalized Older Adults: A Placebo-Controlled Crossover Study. Samaya I.C.,Rienzi B.M., Deegan J.F. and Moss D.E. 2001 Journal of Gerontology.

2. Seasonal Affective Disorder, Kurlansik S. and Ibay A.D. 2013. Indian Journal of Clinical Practice.

3. Neurobehavioral Aspects ofOmega-3 Fatty Acids:Possible Mechanisms and Therapeutic Value in Major Depression. Logan A.C. 2003. Alternative Medicine Review.

4. Light Therapy for Seasonal Affective Disorder. A Review of Efficacy. Terman M., Terman J.S., Quitkin F.M., McGrath P.J., Stewart, J.W., Rafferty B. 1989. Neuropsychopharmacology.

5. Vitamin D deficiency and depression in adults: systematic review and meta-analysis

Rebecca E. S. Anglin, Zainab Samaan, Stephen D. Walter and Sarah D. McDonald. 2013. The British Journal of Psychiatry.

6. Magnesium and depression: a systematic review. Marie-Laure Derom1, Carmen Sayón-Orea1, José María Martínez-Ortega2, Miguel A. Martínez-González1.2013. Nutritional Neuroscience.

Leave a Reply