What causes depression?

There are many different factors that can trigger depression. These causes are generally divided into three broad groups – biological/physical, psychological and social, described in more detail in Study Session 9.

Biological or physical: Chemical changes in the brain may contribute to the onset of depression. For example, a person's mood can change with hormone levels going up and down. This is sometimes seen in women when depression may occur with the menstrual cycle, childbirth and the menopause. Depression can also follow other known diseases such as goitre (caused by deficiency of iodine in the diet) or low thyroid hormone level, anaemia and some infections. Drinking excess alcohol or some prescribed medications, for example, anti-hypertensive drugs (drugs taken to reduce high blood pressure), can occasionally cause depression.

Psychological: For some people, upsetting events, such as bereavement, divorce, illness and job or money worries can be associated with depression.

Social: Poverty, lack of adequate support and doing fewer activities or having fewer interests can lead to depression. Withdrawal from social contact may happen because of depression and this can lead to a cycle of worsening of depression.

Family history may also play a part. When there is a history of depression in parents or siblings (brothers and sisters), there is a slightly increased risk of developing depression. On the other hand, many people who have a family history of depression never develop the condition.

You should note that depression does not always have an obvious cause. Moreover, there is rarely one single cause of depression — usually, different causes combine to trigger the condition. For example, you may feel low after an illness and then experience a stressful life event, such as bereavement.