In May 2013 the American Psychiatric Association published its most recent edition of the Diagnostic and Statistical Manual (DSM). The DSM is used by clinicians and psychiatrists to diagnose mental health disorders, including Autism Spectrum Disorder. With the release of this latest edition (DSM-V), the previously three separate categories of Autistic Disorder, PDDNOS and Asperger's Syndrome were eliminated and combined under the one term Autism Spectrum Disorder (ASD).
In addition to this change, a diagnosis of ASD will now include severity levels, referred to as specifiers, which are based on the amount of support an individual will need due to challenges with social communication and restricted interests and repetitive behaviors. Co-occurring conditions will also likely impact the assigned severity level. There are three severity levels, detailed in the following table: