There are both predisposing and precipitating factors contributing to someone becoming depressed. Predisposing factors are features of one's personality or lifestyle that make one susceptible to depression. These may be related to genetic factors or to early lifetime experiences or to social circumstances. Precipitating factors are triggers which directly lead to the episode of depression. For example stressful life events such as the loss of a job or the end of a relationship can trigger depression.
Depression can also be a side effect of certain medications.
In depression the metabolism of the brain is affected. Levels of certain brain chemicals are altered. The purpose of antidepressant medication is to rectify any imbalance in the levels of these brain chemicals. D epression is characterised by a persistent low mood which affects the ability to carry out everyday activities . It is more than just feeling 'down' for a short while.