Autistic disorder versus other pervasive developmental disorders in young children: same or different?

Area of Science:

• Developmental Psychology
• Child Psychiatry
• Neurodevelopmental Disorders

Background:

• Pervasive Developmental Disorder-Not Otherwise Specified (PDD-NOS) and Autistic Disorder (AD) are distinct diagnoses within the Diagnostic and Statistical Manual of Mental Disorders.
• Distinguishing between PDD-NOS and AD can be challenging for clinicians.
• Cognitive ability can influence symptom presentation in neurodevelopmental disorders.

Purpose of the Study:

• To compare the cognitive, adaptive, and behavioral profiles of preschool children diagnosed with PDD-NOS, AD, developmental language disorders (DLD), and low IQ.
• To investigate the impact of cognitive subgroups on the characteristics of children with PDD-NOS and AD.
• To examine the diagnostic validity and specificity of PDD-NOS within the autistic spectrum.

Main Methods:

• Comparative study involving preschool children diagnosed with PDD-NOS (N=18), AD (N=176), DLD (N=201), and low IQ (N=110).
• Children were categorized into high and low cognitive subgroups based on a nonverbal IQ of 80.
• Assessment of verbal skills, adaptive functioning, and maladaptive behaviors.

Main Results:

• Children with PDD-NOS exhibited verbal and adaptive skills intermediate between those with DLD and AD.
• PDD-NOS and AD groups showed similar levels of maladaptive behaviors, significantly higher than non-autistic comparison groups.
• Cognitive subgroups within AD demonstrated significant differences in impairment, unlike PDD-NOS subgroups.

Conclusions:

• The behavioral and adaptive profiles of PDD-NOS children closely resemble those of AD children.
• PDD-NOS children occupy an intermediate position between autistic and non-autistic groups across most measures.
• Findings question the diagnostic specificity of PDD-NOS and highlight classification difficulties within the autistic spectrum.