Depression is a very common disorder. It has been estimated that 20% of all women and 13% of all men will develop depression at some time during their lifetime, although much of the depression which exists in the community is unrecognised and untreated. Approximately 75% of the female population and over 50% of the male population attend their general practitioners at least once with a psychiatric complaint, of whom 70% of the women and 34% of the men have a depressive episode. While treatment for some patients will be successful following the acute phase of the depressive episode, it will generally take at least three months and in some instances six months or more to treat an episode. The risk of relapse following treatment is high, affecting approximately 50% of patients treated; furthermore, there is no evidence to suggest that those patients being treated for their first episode of depression are less vulnerable to relapse following response to treatment than those who have suffered previous episodes of depression.