@Ria777 I don’t think that you understand the scientific method. I also have great difficulty understanding your logic. The things you said were a tautology, but had nothing to do with mental health research. Science is about measurable things. You are right that you can’t measure internal states, but you can surely measure behavior and genetic makeup and physical activity inside the brain.
If the levels of various neurotransmitters in a brain are significantly different when comparing normal people with people who exhibit behaviors we call mental illness, they there is a correlation between those things. If, when one compares the changes in the various neurotransmitters when using chemicals, mental techniques or doing nothing, and there is a significant difference in the levels of neurotransmitters and the associated behavior, and there is a significant difference between the various interventions, then you can say that each intervention is correlated with this amount of change in a mentally ill person’s behavior.
I also don’t think you have a very nuanced understanding of the way genes and environment work together. It is a mistake to say that any particular behavior is a result of only one or the other. Genes have the potential to program the body in specific ways that respond to the specific stresses of different environments. Genes contain the programming to respond in a way that makes it more likely the individual will succeed in many different environments.
Some genes seem to be more likely to express as bipolar disorder given the same stress than other genes do. Those genes don’t always result in bipolar disorder because those individuals don’t all experience the stresses that lead to the disorder. It is interesting to speculate on how bipolar disorder can give people a survival advantage in some environments.
It appears to be true that one can manipulate one’s brain chemistry using mental techniques, too. Some people are better at this than others. I liken the choice to use mental techniques or medical interventions to the choice between using a handsaw or a chain saw to cut down a tree. Either tool will do the trick, but one is much slower than the other. The advantage of the slow one is that it works in the absence of fuel.
My preference is to use the easier technique as long as I have fuel, and then revert to the slower and more difficult technique. I think that some people value slower techniques simply because they are natural. I have no problem with that. I do have a problem when people insist that everyone would be better off if they used the hard technique.