Co-morbidity Autism and ADHD

Co-morbidity and factor analysis on attention deficit hyperactivity disorder and autism spectrum disorder DSM-IV-derived items.

Research Center for Psychiatry and Behavioral Sciences, Shiraz University of Medical Sciences, Shiraz, Iran ; Department of Psychiatry, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran.



There is a gap in the literature regarding the extent of possible co-occurrence of attention deficit hyperactivity disorder (ADHD) and pervasive developmental disorders (PDD). This study aimed to investigate co-occurring of ADHD in children with PDD.


A clinical sample of 68 children with PDD was assessed according to DSM-IV criteria to make ADHD and/ or PDD diagnoses. All the different types of PDD were included. DSM-IV derived criteria for ADHD and PDD were analyzed. An exploratory factor analysis was conducted.


The rate of Autism, Asperger syndrome, Rett’s disorder, Childhood Disintegrative Disorder and PDD-NOS (not otherwise specified) was 55.4%, 16.9%, 3.1%, 3.1%, 21.5%, respectively. 53.8% of the sample was with ADHD co-morbidity.

The rate of ADHD subtypes was 37.1%, 22.9%, and 40.0% for inattentive type, hyperactivity/impulsivity type and combined type, respectively.


ADHD and its symptoms highly co-occur with PDD. Meanwhile, the result of factor analysis supports the independence of ADHD and PDD diagnostic criteria.


Further Reading

Brief Report: Prevalence of Attention Deficit/Hyperactivity Disorder Among Individuals with an Autism Spectrum Disorder.

Division of Developmental Medicine, Children’s Hospital Boston, 300 Longwood Avenue, Boston, MA, 02115, USA,


Currently, both the DSM-IV-TR and ICD-10 preclude the diagnosis of Attention Deficit/Hyperactivity Disorder (ADHD) in cases that present with an Autism Spectrum Disorder (ASD).

This criterion will be removed in the upcoming DSM-V, but the relationship between ASD and ADHD, and in particular the prevalence of ADHD among the ASD population, remains controversial.

Previous studies have reported clinically significant ADHD symptoms in one-third to three-quarters of ASD-affected individuals (probands).

In our sample of 1,838 simplex children and adolescents with ASD, we found that less than 16 % met clinically significant levels of ADHD symptoms, per parent report. When both parent and teacher reports were considered, the comorbidity rate was even lower, at 2 %.

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