Recently, a friend's son committed suicide. His father was a pharmacist and knew his son had the genetic mutation, MTHFR, but his son did not want to take supplements. I have had a son who committed suicide who had this mutation and also a granddaughter and grandson who have it that have attempted suicide on several occasions.
It also causes depression, bipolar and other mood problems. I think that many alcoholics, drug, users and others who have addictions or get into trouble a lot have this defect. You discover this by doing a saliva test that costs about $100. and it is treatable by non-prescription medication...either methyl B 12 or methyl folate. depending on the kind of defect. This defect can be found in children and there is a liquid supplements for it.
Basically the problem is that the liver makes glutathione...only the liver, but if you have a genetic deficiency and the liver is not making it the liver cannot detox thus causing mental problems (all disease starts in the gut). and addictions and even illness and heart disease. Taking the methyl form of supplements counter acts the deficiency. Glutathione is essential to the body, but you just can't take it in supplement because of the methylation process.
Here are links for more information.