The third aspect which is important to understand in terms of mental health, and brain/mind dysfunction/illness is thought.
Yes, thought - the thing that a large amount of people consider to be intangible, non-physical, immeasurable. That's simply ignorance. Thoughts are physical things - they are embodied in the electrical pulses, known as action potentials, within neurons.
Our thoughts, our consciousness, our experience of external stimulus and internal stimulus (example: thinking about thinking) has a physical basis in our organic system and thus has the potential to be massively impactful or impacted by the physical system itself.
To put it simply: Emotions affect decisions, decisions affect behaviour, behaviour affects emotions, and so on and so forth.
Furthermore, the concept of neuroplasticity is fundamental to the understanding of how thought can have a massively detrimental impact on our mental function in both a non-physical and physical manner.
The framework, form, and function of our brains predisposes the brain to being receptive and adaptive - what this means is that our brains are malleable on a neurological level by understanding that the receptive nature of the brain promotes adaption and in saying that the receptivity of the brain also promotes routine and consistent established stimulus.
This means that our mental experience is predisposed to positive adaption or negative adaption. People can easily find themselves trapped in a vicious cycle involving their emotions, their thoughts, their choices, their behaviours. All of which impact upon each other increasing the severity of the vicious cycle.
