Autism spectrum disorders (ASD) are a classification of developmental brain disorders that exhibit a wide range of symptoms, skills and levels of impairment or disability. Some individuals are mildly impaired by their symptoms, but others are severely disabled. The Diagnostic and Statistical Manual of Mental Disorders (DSM-5) defines ASD diagnostic criteria as:
1. Persistent deficits in social communication and social interaction across multiple contexts, as manifested by:
- Deficits in social-emotional reciprocity, such as abnormal social approach and failure of normal back-and-forth conversation.
- Deficits in nonverbal communicative behaviors used for social interaction, such as poorly integrated verbal and non-verbal communication.
- Deficits in developing, maintaining, and understanding relationships, such as difficulties adjusting behavior to suit various social contexts.
2. Restricted repetitive behavior, interests, or activities, as manifested by:
- Stereotyped or repetitive motor movements, use of objects, or speech.
- Insistence on sameness, inflexible adherence to routines, or ritualized patterns of non-verbal behavior.
- Highly restricted, fixated interests that are abnormal in intensity of focus.
- Hyper or hypo-reactivity to sensory input or unusual interests in sensory aspects of the environment
The DSM-5 classifies Autistic Disorder, Asperger's Disorder and PDD-NOS (Pervasive Developmental Disorder - Not Otherwise Specified) as Autism Spectrum Disorders.
These examples are not exhaustive of the full DSM-5 criteria.
Approximately 1 child out of 88 is diagnosed with an ASD. This statistic has been increasing rapidly, potentially due to an actual increase in prevalence, a higher awareness about the disease and access to services, or a combination of both.
ASD is diagnosed via screenings and evaluations. Boys are nearly five times as likely to be diagnosed as girls (1 in 54 boys vs. 1 in 252 girls). Girls are also less likely to be diagnosed with ASD because they may have inherently stronger social skills. However, their other cognitive deficiencies are more pronounced and several associated disorders, such as Fragile X Syndrome, are x chromosome-linked. As a result, ACE scientists have decided to make girls the target population, granting researchers the opportunity to explore genetic causes while providing the research necessary to properly diagnose and treat children with ASDs.
Lower prevalence exists among Hispanic children than non-Hispanic black children, who in turn have a lower prevalence than non-Hispanic white children. A CDC analysis revealed that 38 percent of children with ASDs are classified as having an intellectual disability, 24 percent were borderline, and 38 percent had average or above average IQ.
There is a lower sex ratio among later-born children than for first affected children. The ratio also decreases with increased parental age. Genetic mechanisms leading to ASD differ between simplex (single affected child) and multiplex (multiple affected children) families.
Monozygotic twins only share the condition 60-92 percent of the time. Such variability indicates environmental factors may be significant contributors to the disorder.