Depression is what your mind does when its trying to solve a problem in your life.  It focuses the mind.  Depression for a robot would be when it freezes or slows to focus internally to figure out what it needs to change to avoid future failings.,(reply>), Also when the biochemistry is off. From diet, genetics, lifestyle, and  working through past experiences with a bag of meat between the ears that is essentially injured from the factors I mentioned plus others.  The bag goes to the end if spine and the fascia system in the rest of the body is interconnected and holds onto things that can be released. So I see the answer similarly to your comment.