Causes of depression

Hormonal causes
Women experience depression about twice as often as men. Many hormonal factors may contribute to increased rate of depression in women, particularly such factors as menstrual cycle changes, pregnancy, miscarriage, postpartum period, pre-menopause, and menopause.

Many women are also particularly vulnerable after the birth of a baby. The hormonal and physical changes, as well as the added responsibility of a new life, can be factors that lead to postpartum depression in some women. While short-lasting "blues" are common in new mothers, a full-blown depressive episode is not a common occurrence and requires active intervention.

Hormonal changes may also be responsible for the onset of depression in men. Recent research suggests that a decrease in testosterone can lead to the development of depression in older men.

Physical illness
Mood change and depression are more common in people suffering from physical illnesses than in people who are well. Although a person can develop depression in association with almost any physical illness, some diseases are more likely to lead to depression than others.

The cause of these depressions is unclear but there is good evidence that some illnesses directly affect the parts of the brain and the chemical systems that control our mood and behaviour. Below are some of the more common conditions in which depression is likely to occur:

Parkinson's disease: About 40% of those with Parkinson's disease will suffer from an episode of depression

Dementia: People with dementia suffer from more depressive symptoms and more depressive illnesses than other people

Multiple sclerosis: Depression is more common in this condition

Heart disease: Depression is more common in people with heart disease. It is increased in those suffering from angina, and is two to three times more common in people after a heart attack

Stroke: Depression is much more common in people after a stroke and is probably increased in people having 'mini strokes' too

High blood pressure (hypertension): Studies have shown this also leads to increased rates of depression

Hypothyroidism: Low levels of thyroid hormones can lead to depression, which may be very severe

Cushing's syndrome: This is a rare disease caused by an excess of certain steroid hormones that can lead to severe depression

Infections: Certain viral infections, for example glandular fever and influenza, are prone to trigger depression in vulnerable people

Depression can so be seen to be more common amongst people with a number of forms of chronic illnesses, and so should be an important consideration within long term maintenance and treatment plans.

Medication and depression
Certain types of medication are associated with increased rates of depression. These include:

Calcium channel blockers e.g. nifedipine, nimodipine, verapamil
Beta-blockers, e.g. propranolol, atenolol, metoprolol
Corticosteroids e.g. dexamethasone, hydrocortisone
Levodopa e.g. madopar, sinemet

If depressive symptoms develop after taking a new medicine, then advice should be sought from a doctor about whether to try an alternative.

Past experiences can effect the way we feel about ourselves in the present, and if that feeling is negative it can have a long term effect. Depression often begins with a stressful event, such as a divorce, losing a job or being assaulted.

It is not the event itself that causes depression, but the whether we have the opportunity or the ability to deal with it. If feelings are not expressed at the time this can contribute towards depression. For example, if a person experiences loss, it is important to for them to acknowledge how they feel and grieve in order to move on.