Regressive autism

Regressive autism is a manner of the neurological development of an autistic child in which they first develop some non-autistic skills, such as speech, and then start to lose those skills at about the age of 18 months, thereafter following the standard pattern of autistic neurological development. The term refers to the superficial appearance that their neurological development has reversed; really it is only the few specific skills, rather than the neurology as a whole, that regresses. It is more usual for autistic neurological development to not include such aberrations, with age-appropriate autistic symptoms being clear from birth, in which case the term "early infantile autism" is used.

The temporarily-acquired skills typically amount to a few tens of words of spoken language, and may include some rudimentary social perception. Skill loss may be quite rapid, or may be slow and preceded by a lengthy period of no skill progression. In some cases a child will go through a period of learning new words at the cost of losing previously-acquired words.

The apparent mental regression of regressive autism is surprising and distressing to most parents who encounter it, much more so than having a child who is obviously autistic to start with. The pattern of symptoms naturally leads many to suspect that postnatal environmental factors play a part in causing autism. In particular, because obvious symptoms start at about the age that children receive several vaccinations, some parents perceive a causal link between the two, especially if skill loss is rapid. Although some controversy remains, the prevailing understanding is that autism is caused by prenatal biochemistry, and thus the perception of a link with vaccination (or other postnatal factors) is mistaken.