A term popularized by developmental psychologist Gordon Neufield, “acquired self-esteem” refers to one’s self-worth being contingent upon external validation, such as achievements or the estimation of others. Maté believes that this reveals a lack of self-respect and prevents the growth of a true self, particularly in individuals with ADD.

“Attunement” is the harmonious attachment relationship between an infant and a caretaker. More specifically, it refers to the caretaker’s responsive involvement in the infant’s emotional world. Maté believes this relationship is critically important to the long-term development of emotional self-regulation and attention; the absence of attunement is foundational to his theory of ADD and thus to the book’s overarching claims.

As opposed to the voluntary nervous system, the ANS is composed of the smooth muscles that line the body’s organs and operate involuntarily. The ANS is made up of the sympathetic nervous system and the parasympathetic nervous system. Maté cites the fact that both the ANS and emotions are processed by the same part of the cortex to support his contention that emotions influence the body’s physiological state, which is in turn key to his ideas about how ADD develops.