What is seasonal affective disorder (winter depression)?
The terms 'winter depression' and seasonal affective disorder (SAD) describe a form of depression that occurs in the winter months. Women are affected more often than men.
The prominent symptoms are:
- low mood starting in autumn or winter
- lack of energy
- overeating and weight gain (there is often a craving for carbohydrate food)
- lack of interest in socialising
- increased sleep and daytime sleepiness.
Opinion is divided as to whether this is a separate disease from other forms of depression, although there does appear to be a group of people that suffer with it on a regular basis starting each autumn or winter and then recovering in the following spring or summer.
It's unusual for these symptoms to be of sufficient severity for them to be brought to the attention of doctors but for those individuals who do find that they need medical help, all the usual medication and psychological treatments may be tried. There have also been reports of successful treatment using exposure to bright light.
There is a small proportion of people with regular winter depression who find that their mood does not simply return to normal in the spring or summer, but that it becomes excessively high.
It's possible that these individuals have a seasonal bipolar affective disorder (seasonal manic depression) and the mood stabilising treatments for the more common non-seasonal form of the illness are available.
What causes winter depression?
In some people the apparent relationship to the seasons is simply because of stresses and difficulties that regularly happen for them at that time of year.
The illness these people suffer from would seem to be little different to any depressive illness that is triggered by a stressful event.
Where a regular precipitating event does not occur, the cause is not known. It is possibly related to the reduction in natural light and the lower temperatures in the winter months but this is uncertain.
The levels of sunlight can influence the activity of certain chemicals in the brain, such as melatonin and serotonin. These in turn can influence mood. In some people, seasonal affective disorder seems to run in families – so genes may play a role.
How is it treated?
The treatment for seasonal affective disorder is the same as for other types of depression. This includes:
- antidepressant medication
- psychological therapy, such as cognitive behavioural therapy
- physical activity.
In addition, bright light therapy has been used for seasonal affective disorder.
This consists of the sufferer having a special lamp or light box at home, which provides a strong source of light.
Research in this area has shown mixed results, and the research studies have used a variety of light sources and methods.
Overall the evidence suggests that light therapy may bring short-term benefits to improving mood. But the symptoms tend to recur if the light therapy stops.
The National Institute for Health and Care Excellence (NICE) has examined the evidence for light therapy and found it to be inconclusive overall, as some benefits may be due to a placebo effect.
Other people also read:
Bipolar affective disorder (manic depression): what symptoms are involved?
Depression: how is depression diagnosed?
Treatment of bipolar affective disorder: what drug treatments are there.
Sleep and depression: what sort of sleep problems can affect people with depression.
From Drugs and Therapeutics Bulletin. Clinical Review. Management of seasonal affective disorder. BMJ 2010;340:c2135.
National Institute for Health and Care Excellence. Depression in adults (update). 2009.