Historically we've considered mental health and illness as coming from either one's life experiences or coming from one's genetics or biology. We've mistakenly considered the the brain separate from the rest of the body. We are more interconnected than those outdated views suggest. Our physical health impacts our brain health. Likewise, we experience emotions (fear, anger, sadness, and joy) not only in our brains, but in our bodies. Emotions influence our brain's biochemistry, and our biochemistry impacts our emotions, bodies and how we experience our lives.
A perfect example of this is Pyrrole Disorder - an inborn error of pyrrole chemistry. Those who are affected make an excessive amount of this metabolite. Pyrroles themselves are not a problem and do not cause disease. We all have them. They do however, bind Vitamin B6 and Zinc. When pyrroles leave the body (through urine), they take some B6 and zinc with them. This is not a problem either. The problem comes when pyrroles are being overproduced for genetic reasons or because of physical or emotional stress. This can lead to severe B6 and zinc deficiencies.