Structural Validity of the Psychopathology in Autism Checklist Among Children and Adolescents.
The PAC is ready for routine mental-health screening in autistic youth with ID—just treat the psychosis subscale as tentative.
01Research in Context
What this study did
Halvorsen et al. (2025) tested if the Psychopathology in Autism Checklist (PAC) measures the same three mental-health areas in children and teens with autism plus intellectual disability.
They ran a confirmatory factor analysis on parent answers. The sample was youth already diagnosed with autism spectrum disorder, intellectual disability, or developmental delay.
What they found
The three-factor PAC structure held up. Most subscales showed good internal consistency, meaning items within each scale hang together.
The psychosis subscale was the weak link. It did not reach acceptable consistency, so clinicians should interpret those scores with caution.
How this fits with other research
Hilton et al. (2010) first showed the PAC works in Norwegian adults with autism plus ID. Halvorsen et al. (2025) extends that work downward to children and teens, keeping the same three-factor shape.
Kildahl et al. (2025) also ran a confirmatory factor analysis in the same population but used the Aberrant Behavior Checklist (ABC). Both studies found four of five subscales held up, suggesting checklists generally work in this group.
Irvin et al. (1998) and Repp et al. (1992) earlier proved the PAS-ADD and ABC are solid for people with ID. The new PAC data now give clinicians a third, autism-focused option for youth.
Why it matters
You now have a free, 29-item parent form that flags anxiety, mood, and behavior problems in autistic clients with ID. Use it during intake or annual reviews. Skip the psychosis subscore or follow it with a clinical interview. Pair it with the ABC or PAS-ADD if you need broader or adult data.
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02At a glance
03Original abstract
BACKGROUND: The use of instruments developed for people with autism spectrum disorder (ASD) and intellectual and developmental disabilities (IDDs) is recommended for assessing mental health in these groups. This is the first study to investigate the structural validity and internal consistency of the Psychopathology in Autism Checklist (PAC) among autistic children and adolescents with IDDs. METHODS: A total of 600 children aged 2-19 years (M = 9.2 years, SD = 4.5 years, 66% male) with IDDs (full-scale IQ M = 81.29, SD = 18.65) participated, including 194 individuals with ASD. Parents completed the PAC, Strengths and Difficulties Questionnaire (SDQ) and Vineland Adaptive Behaviour Scales (VABS). Full-scale IQ was assessed using an individualised intelligence test, and the extent of autism characteristics was assessed using the Autism Diagnostic Observation Schedule-2. RESULTS: Confirmatory factor analyses revealed acceptable fit indices for a three-factor solution. The internal consistency was adequate for most of the PAC subscales. The PAC showed meaningful overlap and differentiation with the SDQ, VABS, measures of intellectual functioning and a measure of autism symptoms. CONCLUSIONS: Overall, satisfactory internal consistency and validity were found for the PAC (with the exception of the psychosis subscale). These findings provide preliminary support for the use of the PAC in children and adolescents with ASD and IDDs.
Journal of intellectual disability research : JIDR, 2025 · doi:10.1111/jir.70012