People with a family history of depression and/or those who have experienced abuse in childhood are more vulnerable to depression.
Depression is often a reaction to ongoing stressors such as poverty or domestic violence.
Alcohol abuse and physical illnesses are other common causes.
Without treatment, an episode of depression usually lasts 4-6 months, though it can last longer especially if the person has ongoing social problems.
50% of people who have one episode of depression will go on to have further episodes. This is called recurrent depression.