'Paraphilic infantilism' is usually shortened to 'infantilism.' This can lead to some misunderstandings, since 'infantilism' can also mean 'lacking development.' Mental retardation involves never having achieved an average maturity, in contrast to adult babies, who actively set their maturity aside. In turn, psychosexual infantilism, a term coined by Freud, referred to those who haven't "matured" through the psychosexual stages into heterosexuality. Psychosexual infantilism includes paraphilic infantilism as well as other paraphilias and sexual orientations. Finally, regression is a broad term with many meanings. Adult babies regress, but those who regress aren't necessarily adult babies.
Adult Babies and Diaper Girls
BDSM - Diapers are sometimes used during prolonged bondage sessions, not only as a method to control and shame the submissive partner, but also to allow longer periods of bondage. In Total Power Exchange, diapers are sometimes utilized for the dependency they represent of the wearer on their master to be checked and changed.