While the exact cause of depression isn't known, a number of things can be associated with its development. Generally, depression does not result from a single event, but from a combination of recent events and other longer-term or personal factors.
Research suggests that continuing difficulties – long-term unemployment, living in an abusive or uncaring relationship, long-term isolation or loneliness, prolonged exposure to stress at work – are more likely to cause depression than recent life stresses. However, recent events (such as losing a job) or a combination of events can ‘trigger' depression in people who are already at risk because of past bad experiences or personal factors.
- Family history – Depression can run in families and some people will be at an increased genetic risk. However, this doesn't mean that a person will automatically experience depression if a parent or close relative has had the illness. Life circumstances and other personal factors are still likely to have an important influence.
- Personality – Some people may be more at risk of depression because of their personality, particularly if they have a tendency to worry a lot, have low self-esteem, are perfectionists, are sensitive to personal criticism, or are self-critical and negative.
- Serious medical illness – Having a medical illness can trigger depression in two ways. Serious illnesses can bring about depression directly, or can contribute to depression through associated stress and worry, especially if it involves long-term management of the illness and/or chronic pain.
- Drug and alcohol use – Drug and alcohol use can both lead to and result from depression. Many people with depression also have drug and alcohol problems. Over 500,000 Australians will experience depression and a substance use disorder at the same time, at some point in their lives.
Changes in the brain
Although there has been a lot of research in this complex area, there is still much that we do not know. Depression is not simply the result of a ‘chemical imbalance’, for example because you have too much or not enough of a particular brain chemical. There are in fact many and multiple causes of major depression. Factors such as genetic vulnerability, severe life stressors, substances you may take (some medications, drugs and alcohol) and medical conditions can lead to faulty mood regulation in the brain.
Most modern antidepressants have an effect on your brain’s chemical transmitters (serotonin and noradrenaline), which relay messages between brain cells – this is thought to be how medications work for more severe depression. Psychological treatments can also help you to regulate your moods.
Effective treatments can stimulate new growth of nerve cells in circuits that regulate mood, which is thought to play a critical part in recovery from the most severe episodes of depression.
Everyone is different and it's often a combination of factors that can contribute to a person developing depression. It's important to note that you can't always identify the cause of depression or change difficult circumstances. The most important thing is to recognise the signs and symptoms