Co-Occurring ADHD in Autistic Children

Comorbid ADHD in Autism

Autism spectrum disorder (ASD) and attention deficit hyperactivity disorder (ADHD) are neurodevelopmental disorders with onset of symptoms in early childhood. There is an overlap in the clinical presentation of ASD and ADHD with epidemiological studies indicating an increase in prevalence rates of ASD and ADHD over the past decade. Symptoms associated with both disorders often result in significant behavioral, social, and adaptive problems across home, school, and community settings  Research suggests that when ADHD is comorbid with ASD, the risk for increased severity of psychosocial problems increases. More severe externalizing, internalizing  and social problems, as well as more impaired adaptive functioning, have been reported in children with comorbid ASD and ADHD than children identified with only ASD.

Although there continues to a debate about ADHD comorbidity in ASD, research, practice and theoretical models suggest that comorbidity between these disorders is relevant and occurs frequently. For example, studies conducted in the US and Europe indicate that children with ASD in clinical settings present with comorbid symptoms of ADHD with rates ranging between 37% and 85%. However, little is known, about comorbidity rates in nonclinical (community) populations of children. Consequently, there is a major need in the field of autism research to better understand how often clinically significant ADHD symp­toms co-occur with ASD in nonclinical populations, and whether the comorbidity of ADHD with ASD is related to differences in other behavioral characteristics.

 Current Research

A study published in the journal Autism examined rates of parent-reported clinically significant symptoms of ADHD in a community sample of school-aged children (4-8 years) with ASD. The researchers hypothesized that children with ASD and comorbid ADHD would exhibit a more severe behavioral phenotype than those with only ASD. Specifically, they speculated that the comorbid group would have lower cognitive functioning, greater delays in adaptive functioning, higher rates of internalizing problems, and more severe social impairment than children with only ASD when these groups were of similar age. Participants included a sample of 153 children 4 to 8 years of age, consisting of the following classification groupings: Non-ASD (n = 91), ASD-Only (n = 44), and ASD+ADHD (n = 18). Children were evaluated on measures of cognitive functioning, internalizing psychopathology, social functioning and autism mannerisms, and adaptive behavior.

 Results

Data analysis indicted significant between-group differences. Results revealed that mean scores were in the “healthy” range for the Non-ASD group, in the mild to moderately impaired range for the ASD-Only group, and in the severely impaired range for the ASD+ADHD group on measures of social functioning and adaptive functioning, representing a continuum of impairment across groups. Children with ASD and ADHD also had lower cognitive functioning than the ASD-Only group. There were no group differences in parent ratings of symptoms of internalizing psychopathology (mood and anxiety disorders), with none of the groups demonstrating elevated rates of internalizing problems. The researchers suggest that an explanation for this finding may be that symptoms of inattention or hyperactiv­ity may obscure symptoms of anxiety in younger school-aged children. In addition, internalizing problems may be difficult to distinguish in young children with ASD as they may not be aware­ of their internal emotional states and may have difficulty expressing their emotional condition to others due to their ASD-related communication impairment.

The overall results of this study indicate greater impairment in cognitive, social, and adaptive functioning for children with ASD and clinically significant ADHD symptoms in comparison with children identified with only ASD. These findings suggest that ADHD comorbidity may constitute a distinctive subtype of ASD and that these children may be at higher risk of social impairment and adjustment problems. The findings are also consistent with other research reports of more severe social problems and maladaptive behav­iors in children with comorbid ASD and ADHD than children with only ASD.

                                                                              Implications 

The findings of the study have important implications for practitioners in health care, mental health, and educational contexts. Overall, 29% of children with ASD also exhibited clinically significant levels of ADHD. Although lower than rates in clinical samples, the rate of comorbid ADHD indicates that young school-age children with ASD should be assessed for ADHD. If clinically significant ADHD symptoms are identified, and social development does not appear to be responding to intervention, changes in the intervention pro­gram (e.g. intensity, strategies, and goals) may be required. It is also important to note that a significant change in the DSM-5 is removal of the DSM-IV-TR hierarchical rules prohibiting the concurrent diagnosis of ASD and ADHD. When the criteria are met for both disorders, both diagnoses are given. Thus, an assessment of ADHD characteristics should be included whenever inattention and/or impulsivity are indicated as presenting problems. It is imperative that practitioners recognize the high co-occurrence rates of these two disorders as well as the potential increased risk for social and adaptive impairment associated with comorbidity of ASD and ADHD. More research is needed to further clarify the behavioral characteristics of children with co-occurring ASD and ADHD so that specialized treatments and interventions may be designed to improve outcomes and quality of life for this subgroup of children. This is important because children who present with the two disorders may have a higher risk for sub-optimal outcomes and may benefit from different treatment methods or intensities than those with identified with only ASD.

Key References and Further Reading

American Psychiatric Association. (2013). Diagnostic and statistical manual of mental disorders (5th ed.) Washington, DC: Author.

Colombi, C., & Ghaziuddin, M. (2017). Neuropsychological Characteristics of Children with Mixed Autism and ADHD. Autism Research and Treatment, 1-5. 

Doepke, K. J., Banks, B. M., Mays, J. F., Toby, L. M., & Landau, S. (2014). Co-occurring emotional and behavior problems in children with Autism Spectrum Disorders. In L. Wilkinson (Ed.), Autism Spectrum Disorders in Children and Adolescence: Evidence-based Assessment and Intervention in Schools (pp. 125-148). Washington, DC: American Psychological Association.

Kuhlthau K., Orlich F., Hall T.A., et al. (2010). Health- Related Quality of Life in children with autism spectrum disorders: results from the autism treatment network. Journal of Autism and Developmental Disorders, 40(6), 721–729.

Loveland K. A., Tunali-Kotoski, B. (2005), The school age child with autism. In F. R. Volkmar, R. Paul, A. Klin, & D. Cohen (Eds.), Handbook of autism and pervasive developmental disorders: Vol. 1. Diagnosis, development, neurobiology, and behavior (3rd ed., pp. 247-287). New York: Wiley.

Murray M.J., (2010). Attention-deficit/hyperactivity disorder in the context of autism spectrum disorders. Current Psychiatry Reports, 12(5), 382–388.

Rao, P. A., & and Landa, R. J. (2014). Association between severity of behavioral phenotype and comorbid attention deficit hyperactivity symptoms in children with autism spectrum disorders. Autism, 18, 272-280.

Sikora, D. M., Vora, P., Coury, D. L., & Rosenberg, D. (2012). Attention-Deficit/Hyperactivity Disorder Symptoms, Adaptive Functioning, and Quality of Life in Children With Autism Spectrum Disorder. Pediatrics, 130, S91-97. DOI: 10.1542/peds.2012-0900G

Wilkinson, L. A. (2017). A best practice guide to assessment and intervention for autism spectrum disorder in schools. London & Philadelphia: Jessica Kingsley Publishers.

Lee A. Wilkinson, PhD, is a licensed and nationally certified school psychologist, and certified cognitive-behavioral therapist. He is author of the award-winning books,  A Best Practice Guide to Assessment and Intervention for Autism and Asperger Syndrome in Schools and Overcoming Anxiety and Depression on the Autism Spectrum: A Self-Help Guide Using CBT. He is also editor of a text in the APA School Psychology Book Series, Autism Spectrum Disorder in Children and Adolescents: Evidence-Based Assessment and Intervention in Schools. His latest book is A Best Practice Guide to Assessment and Intervention for Autism Spectrum Disorder in Schools (2nd Edition).