An international study led by the University of Edinburgh has discovered more than 100 genes linked to depression.
Experts studied data from two million people in 20 countries.
They found genetic variations affected nerve connections in the parts of the brain controlling decision-making and personality.
The more gene variations their subjects had, the more likely they were to be depressed.
Researchers believe their discovery could lead to better treatments.
Depression will affect one person in six and is the world’s biggest cause of disability.
It can reveal itself as low mood, lethargy, loss of pleasure, no appetite, diminished libido, “tail-chasing” thoughts and more.
Some suffer for a couple of months once in a lifetime. In others it can remain a severe and chronic condition involving admission to a psychiatric hospital and in the worst cases, suicide.
Dr Rebecca Lawrence says everyone is different.
She has a mood disorder which produces spells of depression so severe she receives electro-convulsive therapy (ECT).
Read more at: https://www.bbc.com/news/uk-scotland-47118009