Seasonal affective disorder (SAD)

Seasonal affective disorder (SAD) is a type of depression that follows a seasonal pattern. The symptoms often start in the autumn, when the days begin to get shorter, and they are at their worst in December, January and February. Because of this, SAD is sometimes called "winter depression".

In most cases, the symptoms of SAD begin to ease in the spring and then go away completely.

If you have seasonal affective disorder (SAD), you may notice some of these symptoms:

• low mood
• a loss of pleasure or interest in everyday activities
• irritability
• feelings of despair, guilt and worthlessness
• low self-esteem
• indecisiveness
• tearfulness
• stress
• anxiety
• a reduced sex drive

You may also:

• be less active than normal
• feel tired and sleep more than normal (hypersomnia)
• feel lethargic (lack energy)
• find it difficult to concentrate
• have an increased appetite and eat more than usual (hyperphagia)

For many people, SAD can have a significant effect on day-to-day life.

Talk to a doctor if:

• your mental health is affecting your daily life
• you're not looking after yourself
• you're finding it hard to manage any responsibilities you have

Find out how to get urgent help for your mental health

Doctors don't know the exact cause of seasonal affective disorder (SAD). The symptoms of depression are thought to be linked to less exposure to sunlight.

One theory is that a lack of light in the winter months affects your mood, sleep and appetite, and that this changes how you feel.

SAD is often hard to diagnose, because many other types of depression have similar symptoms. It can take several years before you and your doctor realise that your symptoms are following a regular pattern.

Your doctor might carry out a psychological assessment to check your mental health. During it, you may be asked questions about:

• your mood
• your lifestyle
• your eating patterns
• your sleeping patterns
• any seasonal changes in your thoughts and behaviour
• your personal history
• family history

Your doctor may also do a brief physical examination to look for any other reasons for your symptoms.

A diagnosis of SAD will depend on whether:

• you've had symptoms during the same seasons for 2 or more years in a row
• your periods of depression are followed by periods without depression
• there are any other reasons for your seasonal mood changes

Your doctor will recommend the treatment that suits you best for seasonal affective disorder (SAD). Sometimes this means using more than one treatment together, because that can give you the best results.

Your doctor might offer you cognitive behavioural therapy (CBT), which is a type of talking therapy. It helps you change how you think about and react to the situations that are making you unhappy.

Counselling is another kind of talking therapy. Here you talk to a trained counsellor about your worries and problems.

Light therapy for seasonal affective disorder (SAD) simulates the sunlight that's missing during the darker winter months. The evidence on how well it works is mixed, though.

It may work better if you use it first thing in the morning. Some people find looking at a very bright light uncomfortable.

The results are short-term. Light therapy may help relieve your current symptoms, but SAD may still affect you next winter.

When you buy a light box, make sure you choose one that is:

• made by a fully certified manufacturer
• medically proven to treat SAD

The SAD Association can provide a list of recommended manufacturers.

Very bright light may not be suitable if you:

• have an eye problem or your eyes are particularly sensitive to light
• are taking certain types of medicine, such as antidepressants
• have epilepsy

Speak to your doctor if you're unsure about a particular product, or if you get any side effects while using light therapy.

Doctors often prescribe antidepressants for seasonal affective disorder (SAD) only when the symptoms are severe. The reason is that there's limited evidence they work.

They're thought to work best if you start them at the beginning of winter, before the symptoms appear, and carry on until spring.

Antidepressants can take between 4 and 6 weeks to reach their full effect. Keep taking the medicine as prescribed, even if you begin to feel better.