Depression is a serious mood disorder that involves feeling consistently sad for a prolonged period of time.

The condition can include feelings of sadness and loss of hope, a loss of interest in things that used to be enjoyed, anxiety, bad sleep, a loss of appetite and a low sex drive, decreased energy, moving or talking slowly, and difficulty in concentrating, remembering or making decisions. A person may also have thoughts of suicide or self-harm.

Symptoms of depression range in severity from mild to severe.

A doctor can diagnose depression by asking a person questions about how they are feeling and about their general health. They may also first carry out physical tests, such as urine or blood tests, to rule out other causes for their symptoms. A person should contact a GP if they have symptoms of depression every day for more than two weeks, for most of the day. This is particularly important if thoughts of self-harm or suicide are present, or there are symptoms which are affecting relationships, work or other interests and are not improving.

If depression is mild, a doctor may suggest allowing time to see if the condition improves while monitoring progress. Exercise, self-help books, mindfulness and support groups may be useful at this point.

For moderate depression, talking therapies like counselling and cognitive behaviour therapy may be appropriate treatments.

For severe depression, antidepressant medications may be used, potentially in combination with counselling and other talking therapies.