Depression is Very common More than 10 million cases per year (India) Treatable by a medical professional Medium-term: resolves within months Requires a medical diagnosis Lab tests or imaging rarely required Possible causes include a combination of biological, psychological and social sources of distress. Increasingly, research suggests that these factors may cause changes in brain function, including altered activity of certain neural circuits in the brain. The persistent feeling of sadness or loss of interest that characterises major depression can lead to a range of behavioural and physical symptoms. These may include changes in sleep, appetite, energy level, concentration, daily behaviour or self-esteem. Depression can also be associated with thoughts of suicide. The mainstay of treatment is usually medication, talk therapy or a combination of the two. Increasingly, research suggests that these treatments may normalise brain changes associated with depression.