Two diagnostic criteria are frequently used by clinicians to make an ASD diagnosis: the Diagnostic and Statistical Manual of Mental Disorders-5[1](DSM-5) and the International Disease Classification (ICD). Because both criteria are similar, this section will focus only on the DSM-5 criteria. Keep in mind that, no matter which criteria are used, the clinical manifestation of ASD will vary across individuals.
According to the DSM-5, a diagnosis of ASD requires the presence of persistent difficulty with social communication and interaction in all three of the following categories: social-emotional reciprocity (e.g., failing to engage in mutually agreeable back-and-forth conversation, difficulty initiating or responding to social interactions); nonverbal communication behaviors (e.g., poor eye contact, lack of facial expressions, misunderstanding use of gestures); and developing, maintaining, and understanding relationships (e.g., difficulty adjusting behavior to suit various social contexts). The DSM-5 diagnosis also requires the presence or history of at least two restricted and repetitive behavior patterns, interests, or activities. These include repetitive movements, inflexible adherence to routines, fixated interests, and hyper-reactivity or hypo-reactivity to sensory input.