Causes of depression

Several things can cause depression. Being diagnosed with cancer is enough to trigger an episode of depression in some people.

Other life events such as a death in the family, relationship problems, having a baby, or losing your job can also start off a depressive episode.

Chemical imbalance in the brain

Depression can be linked to a chemical imbalance in the brain. This usually involves a drop in the level of chemicals in the brain called neurotransmitters.

Neurotransmitters take messages from your brain to your nerve cells. The common ones involved in depression are serotonin, norepinephrine, and dopamine.

Such a chemical imbalance can be triggered by a physical or emotional (psychological) event in your life. Sometimes it is hard to know if it was one or the other. Often both types may play a part.

Illnesses that cause depression

Some serious illnesses, such as cancer and Parkinson’s disease, are more likely to cause depression than others.

The physical effect of illness

Doctors think this is because of the physical effect rather than the emotional one. Some other diseases, which are as serious, don’t cause the same amount of depression. We don’t fully understand why this is.

Changes in hormone levels

Changes in hormone levels may contribute to depression in some people. The lower levels of some hormones during menopause can cause depression.

Many treatments for cancer affect your hormone levels including:

• surgery to remove your ovaries and womb
• hormone treatments for prostate cancer or breast cancer

A family history of depression

We now better understand why some people are more likely to become depressed than others. One reason is a family history.

If you have a close relative who has had depression, you are more likely to get depressed yourself when faced with a period of stress.

Sometimes the chemical changes in the brain that go with depression are long lasting. This means that after recovering from an episode of depression, you are more prone to depression being triggered in the future.

More information

Maudsley Learning, part of the South London and Maudsley NHS Foundation Trust, has a set of cancer and mental wellbeing videos for people affected by cancer.

The videos have information and advice on what to do if a cancer diagnosis affects your mental health. They cover several topics, including breaking bad news, managing anxiety, common reactions to a diagnosis, and relationships.