Infantilism (physiological disorder)

In medicine, infantilism is an obsolete term for various, often unrelated disorders of human development, up to developmental disability, which consist of retention of the physical and/or psychological characteristics of early developmental stages (infant, toddler, child, adolescent) into a relatively advanced age. Various types of infantilism were recognized, lumped together in the above superficial description.

Source: Wikipedia — Infantilism (physiological disorder) (CC BY-SA 4.0)