Most people assume that depression is caused simply by recent personal difficulties. Depression however, is often caused by the mix of recent events and other longer-term or personal risk factors.

Research indicates that ongoing difficulties, such as long-term unemployment or living in an abusive or uncaring relationship, are more likely to cause depression than recent life stressors. Depression can also run in families and some people will be at increased genetic risk. However, this doesn't mean that you will automatically become depressed if a parent or close relative has had the illness. Life circumstances are still likely to have an important influence on your chances of becoming ill.

It's also common for people to experience depression and anxiety at the same time.

Common medical causes of depression include: 

• Low thyroid function
• Brain injuries and diseases (eg. stroke, heart disease, head injury, epilepsy, Parkinson's Disease)
• Some forms of cancer
• Infectious diseases
• Blood vessel disease in the brain due to diabetes and/or hypertension
• Some steroid and hormonal treatments
• Anaemia
• Chronic pain
• Quitting smoking.

High-risk personality being: 

• A lifelong worrier
• A perfectionist
• Sensitive to personal criticism
• Unassertive
• Self-critical and negative
• Shy, socially anxious and having low self-esteem.

Common tests done by a doctor include: 

• Full blood count and biochemistry
• Thyroid function tests
• Urine test for sugar and protein
• Occasionally, a brain scan.

It's important to note that you can't always identify the cause of depression nor change troubling circumstances. The most important thing is to recognise the depression and to seek help.

Remember, the sooner you get treatment, the greater the chance of a faster recovery.