then he had to smile to himself , for once he was certified and begun to practice he had also discovered that his chosen profession provided possibly the best job security in the country , along with an unlimited source of income , the usiwhich is how many of his colleagues had nicknamed the dsmsince they , as a body , could create new mental disorders pretty much at will by adding the word disorder to any one of possibly millions of normal human conditions , and then include them in the dsm , their billing manual .