Hi, all of this sound like progress to me, especially the ability to recognize (the "here it comes") the onset of the depressive episode, and the fact that it resolves. Early in my recovery I experienced the same thing, I would start crying for no particular reason, than later it would self-resolve.

I can’t answer what’s causing it, other than the general statement that the neuro pathways are altered by brain trauma. For the symptoms you describe, I have found mindfulness practice and meditation helpful. By recognizing “here it comes’, he is already aware at some level. Mindfulness teaches to recognize and accept our feeling and emotions in a non-judgmental way. I say to myself “I’m having feelings of anxiety right now” or “feeling of depression right now”. When I accept these feelings in a non-judgmental way, they resolve more quickly and reoccur less.

Here is a link I found if you are interested.

http://www.mindfulnessinfo.com/

Best to you both.