The misnomer of ‘high functioning autism’: Intelligence is an imprecise predictor of functional abilities at diagnosis

Gail A. Alvares, Keely Williams, Dominique Cleary, Kiah Evans, Emma Glasson, Murray Maybery, Sarah Pillar, Mirko Uljarevic, Kandice Varcin, John Wray, Andrew J. O. Whitehouse

Research output: Contribution to journalArticlepeer-review

135 Citations (Scopus)

Abstract

‘High functioning autism’ is a term often used for individuals with autism spectrum disorder without an intellectual disability. Over time, this term has become synonymous with expectations of greater functional skills and better long-term outcomes, despite contradictory clinical observations. This study investigated the relationship between adaptive behaviour, cognitive estimates (intelligence quotient) and age at diagnosis in autism spectrum disorder. Participants (n = 2225, 1–18 years of age) were notified at diagnosis to a prospective register and grouped by presence (n = 1041) or absence (n = 1184) of intellectual disability. Functional abilities were reported using the Vineland Adaptive Behaviour Scales. Regression models suggested that intelligence quotient was a weak predictor of Vineland Adaptive Behaviour Scales after controlling for sex. Whereas the intellectual disability group’s adaptive behaviour estimates were close to reported intelligence quotients, Vineland Adaptive Behaviour Scales scores fell significantly below intelligence quotients for children without intellectual disability. The gap between intelligence quotient and Vineland Adaptive Behaviour Scales scores remained large with increasing age at diagnosis for all children. These data indicate that estimates from intelligence quotient alone are an imprecise proxy for functional abilities when diagnosing autism spectrum disorder, particularly for those without intellectual disability. We argue that ‘high functioning autism’ is an inaccurate clinical descriptor when based solely on intelligence quotient demarcations and this term should be abandoned in research and clinical practice.

Original languageEnglish
Pages (from-to)221-232
Number of pages12
JournalAutism
Volume24
Issue number1
Early online date19 Jun 2019
DOIs
Publication statusPublished - 1 Jan 2020

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