Bipolar Disorder, Psychosis and Schizophrenia for Dummies who know a little physics etc.
Life is generally in a good position when it has potential (like gravitational potential in the case of high ground) and the capacity to use it in a controlled fashion. That means balancing in a position that would otherwise be considered an unstable equilibrium in the sense of dynamical systems theory. Our bodies are at their most efficient when well balanced (just watch a good dancer to see this in action) and our brains are at their best when similarly balanced. If something disturbs the equilibrium, this disturbance and the required correction can be used to understand the disturbance. This is how stimulation affects us.
Now consider a simple example of a balancing physical object, but with no control mechanism: a spinning top. This has three states--spinning upright (when the gravitational potential is near its maximum), wobbling (when the gravitational potential is slightly lower, in which case it behaves erratically and gives up its energy randomly until...) finally we have the fallen over state. This is what medical people term depression. The simple solution is to get upright and balanced again, but this is hard in our modern overly complex society, and the result of trying to get up is often a lot of wobbling, which gets diagnosed as things like mania, psychosis and schizophrenia depending on how exactly this wobbling manifests itself. The key is to get balanced before you get pushed over, and that is hard when the medical mental health people seem to have the idea that you fix a wobbling spinning top by knocking it over and gluing it to the floor.
Trying to understand mental health in a 'sum of the parts' way is just dumb, but it is the obsession of the medical fraternity, and is to the extent that it is politically very difficult to suggest otherwise. How our genetic code creates us is an approach that misses the point that without the environmental context in which that genetic code develops, it won't develop, so you need to understand the environment as well (and that means understanding the entire world in complete detail, which is rather a long way the other side of impossible).
Viewed as an equilbrium seeking system, 'mental illnesses' like mania and schizophrenia are just seen as things like oscillations and resonant modes that are being excited by either an appropriate drive, or are resonating within the equilibrium seeking system. The biological stuff is just an implementation detail in much the way that transistors on a chip are implementation details of your python program that you are running that you can safely ignore in most cases. Medication is basically trying to solve a software problem by randomly pumping noise into the processor. A computer will crash instantly if you do this, but humans are rather more robust, and can survive for a long time in an unbalanced state. They are, however, rather unproductive in this state and won't tend to find life enjoyable. But they can survive for a long time, but can become desperate to get out of such states.