Ye, it has, and also many other forms of mental illness. > Were our current guidelines to diagnose depressive episodes with around a century ago? Certainly no

Ye, it has, and also many other forms of mental illness. > Were our current guidelines to diagnose depressive episodes with around a century ago? Certainly not, but researchers are very capable of looking at historical records and detect evidence to treated or untreated conditions. Furthermore, people have been describing their own emotions and other people's behaviors since recorded history. There's an army of psychologists, anthropologist, sociologists and geneticists out there studying the history of mental illness. Among many, prof. Sapolsky comes to mind.