The symptom domains are social communication and restricted, repetitive behaviors, with the option of a separate severity - the negative impact of the symptoms on the individual - being specified for each domain, rather than an overall severity. Prior to the DSM-5, the DSM separated social deficits and communication deficits into two domains. Further, the DSM-5 changed to an onset age in the early developmental period, with a note that symptoms may manifest later when social demands exceed capabilities, rather than the previous, more restricted 3 years of age. These changes continue in the DSM-5-TR. Features and characteristics
For many autistic individuals, characteristics first appear during infancy or childhood and generally follow a steady course without remission (different developmental timelines described in more detail below).
Although up to 40% of ASD cases may be linked to genetic causes, it is not currently recommended to perform complete genetic testing on every individual who is diagnosed with ASD. Consensus guidelines for genetic testing in patients with ASD in the US and UK are limited to high-resolution chromosome and fragile X testing. Metabolic and neuroimaging tests are also not routinely performed for diagnosis of ASD.The age at which ASD is diagnosed varies. Sometimes ASD can be diagnosed as early as 14 months, however, a reliable diagnosis of ASD is usually made at the age of two years. Diagnosis becomes increasingly stable over the first three years of life. For example, a one-year-old who meets diagnostic criteria for ASD is less likely than a three-year-old to continue to do so a few years later. Additionally, age of diagnosis may depend on the severity of ASD, with more severe forms of ASD more likely to be diagnosed at an earlier age. Issues with access to healthcare such as cost of appointments or delays in making appointments often lead to delays in the diagnosis of ASD. In the UK the National Autism Plan for Children recommends at most 30 weeks from first concern to completed diagnosis and assessment, though few cases are handled that quickly in practice. Lack of access to appropriate medical care, broadening diagnostic criteria and increased awareness surrounding ASD in recent years has resulted in an increased number of individuals receiving a diagnosis of ASD as adults.