Can raising or lowering ones intelligence and emotional intelligence affect mental illness?

Yes.

What I have noticed is that many people who identify as mentally ill are highly intelligent. It’s almost as if a string has been twisted in a genius brain, that makes the entire person function abnormally.

Since that is the case, I’m not certain that anything can cause that ‘string’ to fix itself.

Nutrition education may help, but for the lady who spends her last ten dollars on cat food, and eats it herself since that’s all she has, I’m not sure that would help. (true story btw)

Well, that would depend on the person. I know of someone who is not very smart, and who has serious emotional immaturity. So, yeah. If it were even possible to increase her intelligence and her emotional maturity it could help a lot.

I believe our brain is like most of our body, the more it’s used, the better it gets.

The answer to this question, mental illness is caused by faulty processing of information within the brain, and not related to level of intelligence.

I think the brain of people suffering from major mental illnesses, such as schizophrenia, has problems with the communication and coordination between various mental functions that interfere with the development of emotional intelligence. Cognitive therapy and possibly physical and nutritional therapies may help, but without a better scientific understanding of how the mind works a cure for such illnesses continues to be elusive.