Are the "autistic traits" and "broader autism phenotype" concepts real or mythical?

The concepts “autistic traits” and “broader autism phenotype” are not officially recognised by the diagnostic authorities. The broader phenotype of autism is regarded as a sub-clinical presentation of behaviours or traits qualitatively similar to features associated with autism and often referred to as “autistic traits”. We consider how the concept of a broader autism phenotype originated, undertake a brief review and comparison of the theoretical perspectives on autism and “autistic traits”, analyse the statement sets in four instruments used for identifying so-called “autistic traits”, and review the justifications for a broader autism phenotype. We conclude that the concept of “autistic traits” arises from a misuse of language, that the absence of autistic traits indicates that there is no such thing as a “broader autism phenotype”, and that apparent evidence for the existence of a broader phenotype is more likely evidence for the population of autistic people being larger than suspected.