There will sometimes be a clear reason for becoming depressed, sometimes not. It can be a disappointment, a frustration, or because you have lost something or someone important to you.
There is often more than one reason, and these will be different for different people. We describe a few of the common reasons below.
Life events and personal circumstances
Depression can be triggered by a stressful or distressing event, such as a bereavement or even changing school or moving to a different place.
Sleep, diet and exercise can all affect our mood and how we cope with things.
Physical health problems, particularly those that are serious or long-term, can cause depression or make it worse. These include:
- life-threatening illnesses like cancer and heart disease
- long-term and/or painful illnesses, like arthritis
- viral infections like 'flu' or glandular fever – particularly in younger people
- hormonal problems, like an under-active thyroid
- conditions affecting the brain or nervous system.
Some people may be more vulnerable to depression than others. This may be because of difficult childhood experiences or trauma, which can include abuse (physical, sexual or psychological), neglect, witnessing violence or a traumatic event, or an unstable family environment.
Alcohol and drug use
Regular heavy drinking or using drugs like cannabis can make someone more likely to become depressed in the long-term.
For more information see our leaflet on alcohol and depression.
Similar genetic ‘risk factors’ are involved in whether someone develops severe depression, bipolar disorder or schizophrenia. There are also environmental risk factors, and these can interact with genetic risk factors to increase or decrease someone's risk of developing these conditions.
For example, someone might have genetic risk factors that mean they are more likely to develop severe depression. However, if they grow up or live in a stable and positive environment this may reduce their risk of developing a serious mental illness.
Having a parent with a serious mental illness like severe depression is the strongest known risk factor for someone developing a serious mental illness . Children with a parent who has a serious mental illness have a 1 in 3 chance of developing a serious mental illness themselves.
When thinking about the causes of developing depression, it is important to remember that lots of different things are involved, and that no one risk factor causes depression.