cause of add/adhd

Curious what folks think. My doc is treating my add dot for mercury (detox), my girlfriend is going to some kind of occ therapist and has her dot on some pill (diagnosed add) and my brother also diagnosed add is doing DOR therapy...??? My doc says it's mercury from vaccines & my amalgams, girl friends doc says it is genetic and claims they are close to identifying the "ADD/ADHD" gene. AND my brothers "doc" claims his cerebellum was not fully formed causing his add/adhd, dyslexia etc. and is teaching him "exercises" to rebalance the ocular and oratory nerves..........Why all the conflicting info????