In the last twelve years, a number of peer reviewed studies have demonstrated the elevated incidence of ADHD symptoms within populations of children receiving DSM-IV-TR and DSM-5 diagnoses of Autism, Autism Spectrum Disorder, Asperger’s Disorder and Pervasive Developmental Disorder – Not Otherwise Specified. Previous research by our group and others has, for example, found a significant overlap between these two conditions (Goldstein & Schwebach, 2004; Goldstein and Naglieri, 2009; van der Meer, Lappenschaar, Hartman, Greven, et. al. 2014). Traits of ASD and ADHD are strongly related in the general population as well as in clinical groups. In 2004 we reported that 26% of children in our sample of what was then referred to as Pervasive Developmental Disorder – Not Otherwise Specified, met the criteria for a diagnosis of ADHD – Combined Type, while 33% met the criteria for ADHD – Predominantly Inattentive Type (Goldstein & Schwebach, 2004). Thus, the majority (59%) of those with PDD – NOS or Autism met criteria for Comorbid ADHD. The percentage of children with ADHD comorbid with Autism Spectrum Disorder is still not completely understood, but there is a significant overlap (Mayes, Calhoun, Mays & Molitoris, 2012).
It has yet to be clearly demonstrated whether these data suggest a one or two way co-morbidity. The combined group also appears to experience a much higher rate of functional impairment than those youth with ASD or ADHD alone. Self-regulatory problems related to attention, hyperactivity and impulse control are characteristics of ASD and from this author’s view should be considered as part of the future diagnostic criteria for this condition. The omission of this consideration in DSM-5 appears as much an oversight as an intentional effort to not address this issue.
However, improvements were made with the recent publication of the Fifth Edition of the American Psychiatric Association Diagnostic Criteria. However, it is still the case, as noted, that problems with attention, impulse control and hyperactivity are not considered within diagnostic criteria for ASD. For the first time, however, both conditions can be simultaneously diagnosed. Interestingly, the DSM notes that approximately 70% of individuals with ASD may suffer from one co-morbid mental disorder and 40% may suffer from two or more co-morbid mental disorders. When criteria for both ADHD and ASD are met, the DSM 5 recommends that both diagnoses should be given. However, even with these improvements, an appreciation of the relationship between ASD and ADHD has yet to be fully appreciated and recognized by the American Psychiatric Association in the construction of diagnostic protocols.
In this article, I briefly summarize research findings from several sources. First, I review the results of studies involving children with ASD and ADHD that were part of the standardization sample for the Autism Spectrum Rating Scales (ASRS, 2009). Next, I combine data from a number of our studies, allowing comparison of neuro-cognitive abilities for youth with ASD and ADHD. A series of analyses of covariance (ANCOVAs) and multivariate analyses for covariance (MANCOVAs) were conducted to investigate whether scores on the Autism Spectrum Rating Scales can distinguish between the groups when the demographic variables were controlled statistically. The independent variable (IV) of interest was group membership, and the demographic characteristics of the samples (e.g., age, gender, race/ethnicity, parental education level, and geographic region) were controlled for by including these variables as covariates. In an attempt to control for Type I errors that might occur with multiple analyses, a more conservative criterion of p < .01 was used for all F-tests and all planned comparisons. In addition to significance levels, an estimate of effect size (with Cohen’s d) is provided for every effect.
Planned comparisons were made between ASD and ADHD groups. The ASD group scored significantly higher than the ADHD group on all scales, except for the Self-Regulation and Attention scales on both parent and teacher forms. This is not unexpected given that the behaviors assessed on these scales are consistently reported in both populations. Importantly, the youth with ADHD were not rated higher than the youth with ASD on these scales. This finding indicates that problems with attention and self-regulation were just as severe in the ASD group as they were in the ADHD group. The majority of the effect sizes for the significant effects were large (mean d = 1.01, ranging from 0.48 to 1.44 across the two forms). Not surprisingly, the effect sizes for the non-significant planned comparisons were very small, with minimal effects between the ASD and ADHD groups on both the Self-Regulation and Attention scales.
In this sample of over 400 children with ASD and over 250 children with ADHD, we found nearly identical scores for behaviors related to poor self-regulation. These findings suggest that problems with self-regulation are as severe in the ASD group as in the ADHD group. We further found that children with ASD and ADHD, while demonstrating somewhat similar behavioral profiles for problems with attention, hyperactivity and impulsivity, demonstrated different neuro-cognitive profiles. Children with ADHD appeared to have significantly more problems with behaviors associated with planning while those with ASD appeared to have significant more problems with attention to relevant detail.
Based on these data, the following clinical guidelines are recommended:
- Diagnosticians must appreciate that DSM-5 conditions such as ASD and ADHD are diagnosed based on behavior not etiology or neuro-cognitive abilities. Multiple causes can be related to similar behaviors diagnostic of ADHD and ASD. The data set generated thus far strongly suggest the following:
- Youth with ADHD and ASD have different behavioral profiles or behaviors related to social communication and unusual behavior but are essentially identical in patterns of problems related to behavioral self-regulation.
- Youth with ASD and ADHD have different neuro-cognitive profiles. As a group, those with ADHD have poor performance on tasks involving planning. Youth with ASD perform poorly on tasks of attention.
- These findings suggest that youth who have many behavioral symptoms associated with ASD also show evidence of severe limitations in selective sustained and shifting attention.
- Our findings also support that children with ADHD demonstrate a different neuro-cognitive profile than those with ASD. Youth with ADHD were poor in planning while those with ASD were poor on tasks of attention.
- Most importantly, youth with ADHD and ASD combined experienced problems related to two components of executive function deficits (planning and attention), a phenomena that has been well understood and appreciated for many years.
- Diagnosticians, educators and parents need to be aware that the process of assessment and diagnosis are two very different phenomena. The diagnoses of ADHD or ASD are dependent on meeting certain behavioral criteria defined in the DSM-5. These criteria are polythetic in that not all children demonstrate all symptoms. These diagnoses are necessary, however, but not sufficient to develop an understanding and appreciation of the data needed to design effective intervention.
- There is an important line of intervention research to help children develop better planning and attention strategies. These cognitive approaches to behavioral change are increasingly researched, manualized and have demonstrated effectiveness. When these strategies are applied with fidelity, children with these ability weaknesses function better.
- Medications to treat ADHD appear to be equally effective in improving self-regulatory problems in children with ASD. Thus, the increasing number of youth taking stimulants and related medications for ASD is not unexpected (Jahromi, Kasari, et al., 2009).
- Non-medication interventions including activities such as skill building and strategy application are particularly beneficial when parents, educators and mental health professionals apply teaching these strategies with fidelity (Antschel, Polacek, McMahon, et al., 2011).
- There is no peer reviewed available data to suggest children with the combined diagnoses have a unique set of differential traits.
- There is no scientific data to suggest that children with the combined diagnoses experience more problems with anger, anxiety, depression or any other types of adverse, internalizing or externalizing behaviors.
Readers interested in further exploring diagnostic processes and current treatment are referred to Goldstein and Ozonoff (2017) and Goldstein and Naglieri (2013).
Sam Goldstein, PhD, is a developmental neuropsychologist. He is Director of the Neurology, Learning and Behavior Center in Salt Lake City, Utah and an Adjunct Assistant Professor in the University of Utah Medical School. He is Editor in Chief of the Journal of Attention Disorders and sits on six Editorial Boards. He has authored over fifty texts, dozens of book chapters, two dozen peer reviewed articles and seven tests. He also sits on the Board of Directors for the EPIC Players Inclusion Company, a New York City based, neuro-inclusive theatre company dedicated to providing professional performance opportunities to individuals living with developmental disabilities.
Antschel, K.M., Polacek, C., McMahon, M., Dygert, K., et al., 2011). Comorbid ADHD and anxiety affect social skills group intervention treatment. Efficacy with Autism Spectrum Disorders, 32, 439-446.
Goldstein, S. & Naglieri, J.A. (2009). Autism Spectrum Rating Scales. Toronto: Multi- Health Systems.
Goldstein, S., & Naglieri, J.A. (2013). Interventions for Autism Spectrum Disorders. New York, NY: Springer.
Goldstein, S., & Ozonoff, S. (Eds.) (2017). Assessment of Autism. New York, NY: Guilford Press.
Goldstein, S. & Schwebach, A. (2004). The Comorbidity of Pervasive Developmental Disorder and Attention Deficit Hyperactivity Disorder: Results of a Retrospective Chart Review. Journal of Autism and Developmental Disorders, 34(3), 329-339.
Jahromi, L.B., Kasari, C.L., McCracken, J.T., Lee, S.E., et al. (2009). Positive effects of methylphenidate on social communication and self-regulation in children with Pervasive Developmental Disorders and Hyperactivity. Journal of Autism and Developmental Disorders, 39, 395-404.
Mayes, S.D., Calhoun, S.L., Mays, R.D., & Molitoris, S. (2012). Autism and ADHD: Overlapping and discriminating symptoms. Research and Autism Spectrum Disorders, 6, 277-285.
van der Meer, J.M., Lappenschaar, M.G., Hartman, C.A., Greven, C.U., Buitelaar, J.K. & Rommelse, N.N. (2014) Journal of Attention Disorders, e publish ahead of print, PMID: 2819924