" For a person with ADD, tuning out is an automatic brain activity that originated during the period of rapid brain development in infancy when there was emotional hurt combined with helplessness. At one time or another, every infant or young child feels frustration and psychological pain. Episodic experiences of a distressing nature do not induce dissociation, but chronic distress does—the distress of the sensitive infant with unsatisfied attunement needs, for example. The infant has to dissociate chronic emotional pain from consciousness for two reasons. First, it is too overwhelming for his fragile nervous system. He simply cannot exist in what we might call a state of chronic negative arousal, with adrenaline and other stress hormones pumping through his veins all the time. It is physiologically too toxic. He has to block it out. Second, if the parent’s anxiety is the source of the infant’s distress, the infant unconsciously senses that fully expressing his own emotional turmoil will only heighten that anxiety. His distress would then be aggravated—a vicious cycle he can escape by tuning out. "

― Gabor Maté , Scattered Minds: The Origins and Healing of Attention Deficit Disorder