The brain is made from, and runs on, nutrients. Enzymes, proteins, neurotransmitters, hormones, and all brain cells are made of nutrients. Nutrients protect the brain from oxidative stress and toxicity. Nutrients (and environment) determine genetic expression, regulating stimulating and inhibitory brain activity and other brain processes.  All of which underlies the effectiveness of nutrients in schizophrenia, as per the outcomes of Dr Carl Pfeiffer and Dr Abram Hoffer; and in bipolar, autism, learning disorders, violence, and other mental health conditions, as per the extensive database of Dr William Walsh.
https://www.walshinstitute.org/uploads/1/7/9/9/17997321/293801829-pyrrole-and-methyl.pdf