Autism, evolution, and the inadequacy of ‘spectrum’

Lay Summary: Individuals diagnosed with autism display variation in many traits, such as interest and ability in social interaction or resistance to change. Referring to this variation as a ‘spectrum’, defined as a range of values along an axis, understates the extent of such variation and can foster incorrect inferences. In psychiatry, the currently accepted term for a developmental disability characterized by variably impaired social and communicative skills, repetitive behaviors, and restricted interests is “autism spectrum disorder.” “Spectrum,” typically refers to values of a variable distributed along a single dimension, incorrectly suggesting people with autism can be simply ranked as more or less ‘autistic.’ In fact, there are multiple traits that pertain to autism and that can vary somewhat independently, in part due to the evolutionary mechanisms that give rise to risk alleles. Therefore, a new and more accurate clinical descriptor should be adopted. I propose: autism-related disorders (ARD).