The cause of depression is not completely known, but scientists believe genetics and certain environmental factors, such as childhood trauma or severe life stress, can contribute to this mental disorder. People who have a first-degree relative like a parent or sibling with depression appear to have a two to three times greater risk of developing the condition than the general public.
It’s believed that no one single gene causes depression. People inherit a combination of genes from their parents, and certain gene combinations can make it more likely for someone to develop depression. However, some people who develop depression do not have a family history of the mental disorder. Read more in Verywell.