For me it is much more of a physical thing as I experience it. Very low energy levels and lack of motivation are the biggest symptoms. My mental processes are way slowed down and feels like a physical thing. I just want to sleep. I can literally feel how my brain is just not firing right. I don't care about anything or have any interest because I just don't have the mental energy for it. Mood wise I am just numb.

It happens to me when everything is going great and there are no triggers. It is not a matter of starting to think low of myself or getting upset over something or negative thinking getting set up. It just happens out of the blue.

Emotions enter the picture only after I am severely depressed and I feel ashamed because I can't function and I am letting others down. I snap out of it in the same way I went into it. I just snap out of it like a switch gets switched for no apparent reason. Not really anything I can say I did to get me out of it.

It is because of all of that and lots of other reasons that I think for me it is much more a physical thing. So for me I see it as both the causes and the symptoms as very physical. Mental processes are physical.