Autism Spectrum Disorder

Basics

Neurodevelopmental disorder characterized by:
- Delays/impairments in development of social communication and social interaction
- Restricted, repetitive patterns of behavior, interests, or activities
- Symptoms present in early childhood
- Significant impairment in functioning
Diagnostic criteria changes since 2013:
- DSM-IV previously included autistic disorder, Asperger disorder, Rett disorder, childhood disintegrative disorder, and pervasive developmental disorder, not otherwise specified within overall category
- DSM-5 has eliminated these separate diagnoses due to insufficient evidence.
- DSM-5 added severity levels (1 to 3) based on the level of support required.
Associated with specific known genetic disorder (e.g., fragile X) in a minority (15%) of cases
Behaviors exist along continuum with unclear boundaries between trait and disorder.

Approximately 1 in 68 (14.6 per 1,000) of 8 year-old children, according to the Centers for Disease Control and Prevention (CDC) 2016 report
Rate rising over past decades
4 times more common in males than females
- Females are more frequently severely impaired with intellectual disability.

Strong genetic influence: risk in 1st-degree relatives 2–18%; identical twins 35–95%
Multiple genes implicated (>100), suggesting polygenic risk. Approximately 15% of children with autism have identifiable genetic anomaly.
Other risk factors: closer spacing of pregnancies, advanced maternal or paternal age, extreme premature birth (<26 weeks), possible maternal inflammation in utero
Link to vaccinations not supported by scientific evidence
Pathophysiology unknown but may be associated with abnormalities in cortical laminar architecture during prenatal brain development

There's more to see -- the rest of this topic is available only to subscribers.