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Key points
- ADHD and ASD share overlapping genetic factors, and up to 85% of autistic individuals additionally experience ADHD symptoms.
- ADHD and ASD share overlapping characteristics around executive function, the focusing of attention, social behavior, and auditory processing.
- There are also specific executive function and social communication patterns unique to each condition.
Attention Deficit and Hyperactivity Disorder (ADHD) and Autism Spectrum Disorder (ASD) are distinct conditions listed in the American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders, 5th edition. Both conditions have strong genetic components, and their characteristics manifest at a young age. The estimated prevalence of ADHD and ASD in school-aged children are around 5% (Polanczyk & Jensen, 2008) and 1.7% (Baio et al., 2018), respectively.
ADHD and ASD do share some overlapping genetic factors (Rommelse et al., 2010), and up to 85% of autistic individuals additionally experience ADHD symptoms (Leitner, 2014). Both ASD and ADHD are on a spectrum, meaning that individuals can present with varying combinations of characteristics from either condition. Due to the growing recognition of how frequently ASD and ADHD co-occur and their overlapping genetic influences, the most recent DSM allows for dual diagnosis of ASD and ADHD (American Psychiatric Association, 2013).
The defining characteristics of ADHD include difficulty with regulating attention, hyperactivity, and impulsivity. Behaviorally, this may manifest as difficulty staying on track and appearing easily distracted by external and internal stimuli, whether in the context of social conversations or in relation to completing tasks. Hyperactivity may manifest via interrupting others, talking excessively, or finding it difficult to sit still in one place. Children with ADHD may come across as impulsive and impatient, jumping into decisions without thinking through the consequences. For a child to receive an ADHD diagnosis, ADHD characteristics must be present before age 12, appear across numerous contexts, and interfere with their ability to function.
Autism spectrum disorder’s criteria center around social communication and repetitive and restricted behaviors (American Psychiatric Association, 2013). There have been widely documented differences between autistic and neurotypical individuals in in how they interpret mental states of others, and make use of repetitive, fixated, or structured behaviors to regulate sensory input from the environment.
Autistic individuals’ social communication can be influenced by differences in the processing of information in comparison to their neurotypical peers, such as preferring a detail-focused cognitive style (attending to parts of a situation rather than to the bigger context) (Bajda et al., 2021); finding counterfactual reasoning such as hypothetical scenarios challenging (Hutchins et al., 2015); processing implicit emotion (inferred or hinted) in a neurologically unique way (Kana et al., 2016); or differences in sematosensory processing (Wodka et al., 2016).
What ADHD and ASD have in common
ADHD and ASD share numerous overlapping characteristics, particularly around executive functions, the focusing of attention, social behavior, and auditory processing.
Executive functions. Executive functions are frontal brain processes that support individuals in pursuing goal-directed, purposeful behavior, including regulating their cognitive focus. These include working memory, the focusing of attention, impulse control, and planning/organization.
Towners (2022) recently reviewed 58 articles investigating executive functions in individuals diagnosed with ASD, and ADHD, and concluded that both groups of individuals demonstrate difficulties with inhibition, working memory, and attention, as compared to neurotypical peers. He noted that 25% of research studies did not find significant differences in the executive functions of individuals with ASD and ADHD. The majority of studies found that autistic individuals demonstrated greater challenges with cognitive flexibility and planning, in comparison to individuals diagnosed with ADHD, while individuals diagnosed with ADHD tended to find tasks requiring attention and inhibition most challenging.
In addition, both groups tend to find the processing of auditory input challenging, in comparison with neurotypical peers, and both benefited from visual supports supplementing verbal instructions.
Social challenges. Individuals with either diagnosis can experience social challenges, especially in relation to communicating with neurotypical peers. These can manifest in outward behaviors such as appearing off track with topics of conversations, a heightened tendency toward interrupting others, or perceived inattentiveness to details within conversations. Even though these behaviors outwardly appear similar for autistic individuals and those diagnosed with ADHD, their underlying influences vary.
Hutchins et al. (2015) found that children on the autism spectrum have impaired (based on the neurotypical standard) understanding of others’ mental states, which is the primary underlying reason for the difference in their social behavior. The understanding of others’ mental states is frequently referred to as theory of mind, or ToM. On the other hand, a Hutchins et al. study (2015) found no significant differences in the way children diagnosed with ADHD infer the mental states of others, in comparison to typically developing children. Children diagnosed with ADHD, however, have been found to outwardly demonstrate deficits in applied theory of mind skills—that is, in their actual observable social behaviors.
Whereas applied ToM abilities are associated with impaired understanding of others’ mental states for autistic children, for children diagnosed with ADHD they may be due to the working of their executive functions including impulsivity, limited focusing of attention, or limited working memory (Hutchins et al., 2015).
Authors suggested that children with ADHD are particularly likely to show less accuracy of processing other peoples’ mental states under conditions of emotional arousal and may benefit from interventions that explore the accuracy of their interpretations under such conditions.
In summary, despite being listed as separate conditions in the DSM-V, ADHD and ASD share numerous overlapping characteristics around executive functions and the focusing of attention, social behavior, and auditory processing. Individuals diagnosed with ADHD tend to find tasks requiring attention and inhibition particularly challenging, whereas autistic individuals find cognitive flexibility and planning particularly challenging.
Socially, children on the autism spectrum’s relationship challenges are associated with their understanding of others’ mental states and are often accompanied by anxiety around the understanding of implicit social communication rules and coping with sensory processing. For children diagnosed with ADHD, social challenges are related more to an impairment of their executive functions including impulsivity, limited focusing of attention, or limited working memory.
References
American Psychiatric Association. (2013). Diagnostic and statistical manual of mental disorders (5th ed.).
Bojda A., Srebnicki T., Konowałek Ł., Bryńska A. (2021). Weak central coherence - construct conception, development, research methods. Psychiatr Pol, 55(6), 1373─1386.
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Hutchins, T. L., Prelock, P. A., Morris, H., Benner, J., LaVigne, T., & Hoza, B. (2016). Explicit vs. applied theory of mind competence: A comparison of typically developing males, males with ASD, and males with ADHD. Research in Autism Spectrum Disorders, 21, 94–108.
Kana, R. K., Patriquin, M. A., Black, B. S., Channell, M. M., & Wicker, B. (2016). Altered Medial Frontal and Superior Temporal Response to Implicit Processing of Emotions in Autism. Autism Research, 9(1), 55–66.
Leitner, Y. (2014), The co-occurrence of autism and attention deficit hyperactivity disorder in children-what d we know? Frontiers in Human Neuroscience, volume 8, article 268.
Polanczyk, G., & Jensen, P. (2008). Epidemiologic Considerations in Attention Deficit Hyperactivity Disorder: A Review and Update. Child and Adolescent Psychiatric Clinics of North America, 17(2), 245–260.
Rommelse, N. N. ., Franke, B., Geurts, H. ., Hartman, C. ., & Buitelaar, J. . (2010). Shared heritability of attention-deficit/hyperactivity disorder and autism spectrum disorder. European Child & Adolescent Psychiatry, 19(3), 281–295.
Townes, P. (2022). 3.22 Executive Function in ADHD and ASD: A Scoping Review. Journal of the American Academy of Child and Adolescent Psychiatry, 61(10), S235–S235.
Wodka, Puts, N. A. J., Mahone, E. M., Edden, R. A. E., Tommerdahl, M., & Mostofsky, S. H. (2016). The Role of Attention in Somatosensory Processing: A Multi-trait, Multi-method Analysis. Journal of Autism and Developmental Disorders, 46(10), 3232–3241.
