His/her conversations might be atypical and simplified and include some repetitive language or non-functional verbal actions.
The individual might prefer to communicate through signs or technological devices.
Cognitive functioning is diminished, and some people have an IQ below 70.
This presents problems with adaptive behaviors such as self-care and communication.
Someone with severe autism has extreme difficulty interacting with other people.
The child or adult might completely exclude interacting with others and prefer to be alone.
The following sections summarize the DSM-5 three levels of autism as outlined by Autism Speaks.
Individuals with level 3 or low-functioning autism are on the most severe end of the spectrum.
With level 3 autism, there is extreme fixation on a few, often atypical, behaviors to the exclusion of others.
There is marked repetition of the restricted behaviors, and this can severely affect day-to-day activities and engagement with others.
Children and adults with level 1 or high-functioning autism have the mildest degree of the disorder.