Is the prevalence of autism spectrum disorder (ASD) increasing?

Is Autism Increasing?

Yes, the prevalence of autism spectrum disorder (ASD) has significantly increased over the past three decades, with current CDC estimates at 1 in 54 children, representing a massive rise from 2-4 per 10,000 in the 1960s. 1, 2

Understanding the Increase in Autism Prevalence

The reported prevalence of ASD has shown a dramatic upward trend:

• Historical rates: 0.7-10 per 10,000 children in the 1970s-1980s 3
• 1990s: >30 per 10,000 children (10-fold increase from 1970s) 3
• Recent CDC data: Approximately 1 in 54 children (equivalent to 18.5 per 1,000) 2
• Parent-reported prevalence: As high as 1 in 40 children (2.5%) 4

Factors Contributing to the Increased Prevalence

This rise in ASD prevalence is attributed to multiple factors rather than representing a true "epidemic" 1:

1. Expanded diagnostic criteria:

   • Changes in diagnostic definitions and broader spectrum recognition 1
   • DSM-5 changes consolidating previously separate conditions under ASD 1

2. Improved awareness and detection:

   • Better professional and public awareness 1
   • Recommended screening at 18 and 24 months 1
   • Improved case identification methods 1

3. Diagnostic substitution/accretion:

   • Reclassification of children previously diagnosed with other conditions 1
   • Higher acceptance of the diagnosis 1

4. Actual risk factors:

   • Advanced parental age 1
   • Prematurity 1
   • Genetic factors becoming more prevalent

Demographic Patterns in ASD Prevalence

Important patterns in ASD distribution include:

• Gender disparity: ASD is approximately 4 times more common in males than females 1
• Severity variations: Females with ASD tend to have more severe intellectual disability 1
• Socioeconomic factors: Potential underdiagnosis in disadvantaged populations 1

Clinical Implications of Rising Prevalence

The increased prevalence has significant implications:

• Economic impact: Annual cost to the U.S. economy estimated at $268 billion (2015) 1
• Healthcare utilization: Children with ASD have greater healthcare needs and difficulties accessing care compared to children with other conditions 4
• Treatment variations: Of children with current ASD, 27% take medication for symptoms, while 64% receive behavioral treatments 4
• Early intervention importance: Early identification is improving, with average age of diagnosis now around 4 years old, down from previous decades 1

Pitfalls in Interpreting Prevalence Data

When evaluating autism prevalence trends, be aware of:

• Methodological differences: Variations in study design, screening methods, and diagnostic criteria can affect reported rates 1
• Age of screening: Different studies screen children at different ages, affecting detection rates 1
• Geographic variations: Prevalence estimates vary by location and population studied 1
• Incomplete ascertainment: Underdetection of cases in young populations can bias prevalence estimates 3

The substantial increase in ASD prevalence represents both improved recognition and possible true increases in incidence, making it an important public health concern requiring continued monitoring and research into potential environmental and genetic factors.