What Is Seasonal Affective Disorder (SAD)?

Whilst a lot of people have the winter blues (up to 28 percent of us) with a tendency to eat or sleep more, if the symptoms have a significant impact on our quality of life, then it may constitute SAD.

Seasonal Affective Disorder is a serious condition (reports showing between 6 and 30% of sufferers requiring hospitalisation for one period of illness during their lifetime), which affects up to 9 percent of the British population during the autumn and winter months.

The symptoms of SAD fall into a spectrum and are characterised by:

1. Feeling low and depressed at the same time every year with symptoms starting in late autumn and intensifying in January and February and can continue through to April.

2. Feeling excessively tired during the day and the need to sleep longer with difficult getting up in the morning

3. Social withdrawal, loss of pleasure and interests, loss of libido

4. Feelings of irritability, tension, stress and anxiety irritability

5. Carbohydrate cravings (including waking up in the night to eat) and weight gain

6. In severe cases feeling of despair, guilt and worthlessness and suicidal ideation

SAD Diagnosis:

Can be difficult as the symptoms are similar to other forms of depression but relies on patients having symptoms at the same time for two consecutive years followed by relief of the depression in the spring.

Why is it an important diagnosis to get right?

The winter symptoms of SAD share the same characteristics of depression as part of a bipolar spectrum disorder such as eating and sleeping too much and having little energy. Patients with SAD also describe periods of marked mood elevation with increased energy in the spring and this can be difficult to distinguish between hypomanic episodes in clients with bipolar spectrum disorders. Up to 28% of people with Bipolar type 2 spectrum disorders show a seasonal variation which is similar to SAD.

Who is affected by SAD?

SAD is up to three times more common in women of child bearing age than men and rarely found in children or older adults. Some clients with bipolar 2 disorder can show a seasonal variation in mood

What causes SAD?

There is no doubt an evolutionary adaptation for our ancestors living in the northern hemisphere who experienced harsh dark winters. Unfortunately, this evolutionary response does not fit well with our modern lifestyles. Nevertheless, our lifestyles have not helped with SAD as only 10% of us now working outside in daylight compared to 75% of us 200 years ago. The causes of SAD are however complex with some cases having a strong genetic component

With Seasonal changes in mood and behaviour being normally distributed it is thought that SAD could form a continuum between unipolar and bipolar depression

It is thought that the cause of SAD is mediated through the Hypothalamus which produces varying levels of melatonin according to the amount of sunlight which affects our sleep//wake and mood. The “Phase Shift Hypothesis” (less available light in the winter may lead to an inability to synchronise circadian rhythms with the sleep/wake cycle) has less sway these days as we are realising that the timing of light therapy may not particularly important as once thought.

Treatments Available For SAD:


Serotonin reuptake inhibitors are the most effective fro of therapy with fluoxetine or sertraline being started in the Autumn and discontinued in the Spring. Nevertheless, caution must be used in patients who may have an underlying bipolar spectrum disorder


There is increasing evidence that cognitive behavioural therapy may be helpful in alleviating winter depressions and possibly preventing it remerging in the future

Light Therapy

Light therapy can be a very effective and rapid treatment of SAD with an improvement of symptoms within the first week. High Quality light boxes are recommended with the intensity of light being measure in Lux. 10,000 Lux light boxes require patients to spend shorter time (up to 30 minutes) in the vicinity of the light box. Some patients prefer lower Lux light boxes and can have them positioned on the corner of their desks at work. Caution should be used with the use of light boxes with rapid cycling mood disorders and a switch to mania or hypomania being reported in some patients with a bipolar spectrum disorder with a seasonal component. Guidance for buying light boxes can be found on the SADA site.

Simple recommendations for people with SAD:

1. Try and keep a regular routine in terms of eating, exercise, sleeping and awakening to keep a balanced circadian rhythm

2. Sits near the windows when indoors in the winter

3. Eat regular well-balanced meals

4. Spend as much time outside in daylight as possible

For more information about Seasonal Affective Disorder, visit the following links:

If you feel like you could be suffering from Seasonal Affective Disorder, fill in our online contact form to request an appointment.



Winter blues: Everything you need to know to beat Seasonal Affective Disorder by N Rosenthal, The Guilford Press;Fourth Edition (September 4, 2012)