I think it is both physical and mental - they are intertwined. If a person’s hormonal levels - including blood sugar are in balance and they have gotten enough sleep (and water - no dehydration), they can roll better with the ups and downs that life invariably gives us all. If they are physically out of balance in any area, then any little thing can set them off. The trouble is these people are often not disciplined enough to be as rigid with their schedules and habits (including taking any hormonal supplements, regular hours, and drinking enough water).
Likewise, someone can be balanced physically but a big emotional blow can get them just enough off balance mentally that they get lax with the things that keep them in balance physically.
There are two entrances to the downward spiral. I have spent my life trying to get out of harm’s way when someone around me takes that first slippery step.
I was afraid of that. I hate “both”-answers.
(c: