Seasonal Affective Disorder.

It is normal to feel more cheerful and energetic when the sun is shining and the days are longer, or to find that you eat more or sleep longer in winter.

However, if you experience seasonal affective disorder (SAD), the change in seasons will have a much greater effect on your mood and energy levels, and lead to symptoms of depression that may have a significant impact on your day-to-day life.

The symptoms are more prevalent in the dark winter months from December to March and often disappear in the spring and summer months.

Symptoms of SAD can include:

• A persistent low mood
• Irritability
• Anxiety
• A loss of pleasure in normal everyday activities
• Sleeping for longer than normal and finding it hard to get up in the morning.
• Craving carbohydrates and gaining weight
• Feeling lethargic and sleepy during the day
• Sleeping for longer than normal and finding it hard to get up in the morning
• Tearfulness
• Mood changes

Causes of SAD:

The effects of light:

When light hits the back of the eye, messages are passed to the part of the brain that controls sleep, appetite, temperature, mood and activity. If there’s not enough light, these functions are likely to slow down and gradually stop.

Disrupted body clock:

Your brain sets your body clock by the hours of daylight. One theory is that if you experience SAD, the part of the brain that sets your body clock isn't functioning completely and so your body clock slows down, leading to tiredness and depression.

Low serotonin levels:

The brain uses the chemical serotonin to regulate our mood. People experiencing depression have been found to have lower levels of serotonin, particularly in winter. It is thought there may be particularly strong seasonal variations in how this process works in people with SAD.

High melatonin levels:

When it’s dark, the brain produces the hormone melatonin which makes us sleep. When it becomes light again, it stops producing melatonin and we wake up. It has been found that people with SAD produce much higher levels of melatonin in winter than other people. (This is also what happens to animals when they hibernate). The relationship between melatonin and SAD is still unclear. We know that if someone with high melatonin levels is exposed to bright light, their melatonin levels drop to normal. However, trials have shown that even after their melatonin levels have returned to normal, they still experience the depressive symptoms of SAD. This suggests that melatonin is unlikely to be the only cause of SAD.

SAD has also been reported to have be triggered by:

• An unwelcome or traumatic life event, such as:
• A major loss or bereavement,
• An assault,
• A serious/physical illness
• A change to diet or medication
• The use (or withdrawal from) street drugs or alcohol

Treatment

A number of treatments are available for SAD including cognitive behavioural therapy, antidepressants and light therapy.

Things you can try yourself include:

• Trying to get as much natural sun light as possible
• Making your home and work environment as light and airy as possible
• Sitting near windows
• Exercising regularly
• Eating a healthy, balanced diet.
• If possible avoiding stressful situations

Sources:

NHS choices

www.mind.org.uk

Seasonal Affective Disorder; Lurie, Stephen J, Gawinski B, Pierce, et al; American Family Physician, 11/1/2006, Vol 74, Issue 9, P1521-1524