Nothing helps everybody, and some things are healing for a very few (P-5-P for example). Conversely, what helps many can be harmful to a few (some vitamins for example), and what helps a few can be harmful for most (insulin injections come to mind)

A few people who had bad results with electrostimulation reported in the BrainTalk forum that they set the power level way too high and actually caused more damage for that reason.