Personally i don't see an either/or - physiology & psychology (mind/brain) are interrelated/interdependent. So too imo is environment.

So much i think depends upon what models & understandings of reality & the self we're using.

The materialist model is currently very popular, especially with the mainstream.

i wouldn't deny that all kinds of stuff can go on at a brain level - some psychotic states i would see as regressive & primarily concerning brain function. But to me it isn't the full picture - especially regarding the areas of consciousness.