There are many here who have and do still suffer from depression of one form or another. The lows are often tempered by corresponding highs. In a manic phase one can feel invincible and achieve much whereas in the depressive phase life can be almost unbearable or totally not worth continuing. I am not sure if the stable state without the highs and lows would be attractive. The well known depressive Stephen Fry has said he can accept the depression because of the manic phases but has suffered terribly over the years.

In my own case if I had been living thousands of years ago I would have starved to death without the help of a caring community or family as I could be virtually lifeless on a daily basis and even when you know you should make an effort you do not because you just don't care and have a fatalistic approach.

Of course I should not extrapolate from my own personal database but I can accept that depression is a disease that needs a cure. Without the manic phase I can see no useful features of clinical depression. We learn to live with it partly because of the social stigma still attached to mental health failure or emotional breakdown.