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"Diagnosed with ADHD, but the reading and writing difficulties seem like something more" — this is not an uncommon situation. Or the reverse: "Autism spectrum disorder was identified, but we're now wondering about attention problems too." Both are real, and both are common.
Developmental differences rarely arrive alone. LD (learning disability), ADHD, and ASD are clinically distinct concepts, but in the actual children who carry these diagnoses, they overlap more often than they appear separately. When this overlap — called co-occurrence or comorbidity — goes unrecognized, support built around a single diagnosis can leave hidden difficulties accumulating. Over time, those accumulated difficulties can develop into what clinicians call secondary disorders: emotional, behavioral, or social problems that emerge as a consequence of untreated primary differences.
Understanding the epidemiology of co-occurrence is the starting point for preventing that outcome.
Background: A Diagnostic Shift
The DSM-5: Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition; the American Psychiatric Association's standard reference for classifying mental health conditions (2013) was the first edition to allow a concurrent diagnosis of both ADHD and ASD. Previous editions had included an exclusionary rule — if ASD was diagnosed, ADHD was not — but that rule was removed, making it formally possible to recognize and support children with features of both [5]. Research on the overlap between LD and ADHD, and between LD and ASD, had been accumulating for decades before that change; DSM-5 brought the diagnostic framework into alignment with what the evidence had long shown.
Applying a single-diagnosis model to a child carries a specific risk: difficulties that don't fit the primary diagnosis get attributed to character ("lazy," "unmotivated," "doesn't try hard enough") rather than recognized as unaddressed developmental differences.
How Often Do These Conditions Overlap?
ADHD, ASD, and LD
A meta-analysis by Rong et al. (2021) found that approximately 9.8% of children with an ADHD diagnosis also had ASD, and that 50–70% of children with an ASD diagnosis also had ADHD [1]. The asymmetry in these rates reflects differences in sample populations and diagnostic criteria, but in either direction, the consistent finding is that overlap is the norm, not the exception.
On the co-occurrence of ADHD and reading disability (dyslexia: a specific learning disorder characterized by difficulty with accurate or fluent word recognition, spelling, and decoding, despite adequate intelligence and instruction): Willcutt et al. (2010) conducted a detailed analysis of the neurobiological overlap between the two conditions and estimated that 25–40% of children with ADHD have a co-occurring reading disability [3]. A child who can calculate but struggles severely with reading and writing may have ADHD in the background; the reverse is equally possible.
A large twin study by Lichtenstein et al. (2010) demonstrated that ASD, ADHD, LD, tic disorders: conditions characterized by sudden, repetitive, involuntary movements or vocalizations, such as Tourette syndrome, and developmental coordination disorder: a condition causing significant difficulty with motor skills and physical coordination relative to age, not explained by another condition share common genetic risk factors [2]. The co-occurrence of these conditions is better understood not as independent disorders happening to coincide, but as multiple expressions of a shared neurobiological substrate — a conclusion that has become increasingly accepted in the research literature.
Why Co-occurrence Goes Unnoticed
There are predictable reasons why co-occurring difficulties are missed. A child with ASD who also has attention problems may have those attention difficulties interpreted as features of ASD rather than as ADHD. A child with LD who cannot stay on task in class may be seen as avoiding difficult work rather than assessed for ADHD. Once a primary diagnosis is in place, other difficulties can be attributed to it rather than recognized separately.
Seeing a child through a single diagnostic label makes it easy for the rest of their difficulties to pass unexamined.
The Pathway to Secondary Disorders
When primary developmental differences go unsupported, a sequence can unfold. Repeated failure experiences accumulate: unable to answer questions in class, unable to turn in homework, unable to navigate peer relationships. When these repeat, self-assessment drops. Low self-assessment leads to avoidance behavior, which in turn can develop into school refusal or withdrawal.
Mugnaini et al. (2009) studied children with dyslexia and found significantly elevated rates of internalizing disorders: psychological conditions where distress is directed inward, including depression, anxiety, and social withdrawal, as opposed to outward behavior problems — depression and anxiety — in the absence of appropriate support [4]. The risk appears to concentrate around the transition to middle school, when academic demands increase and self-comparison with peers begins in earnest.
Pennington et al. (2019) emphasize comprehensive assessment for children with multiple developmental differences and argue that "understanding the full picture of what the child is actually experiencing matters more than the number of diagnostic labels" [6].
Practical Takeaways
Take "something still feels off" seriously
One reason co-occurring differences are identified late is the reassurance that a diagnosis provides. "We already got a diagnosis (or were told to watch and wait), so we're covered." If difficulties that don't fit the existing diagnosis continue, requesting a broader reassessment is a reasonable next step.
Seek consultation early if multiple differences are suspected
Developmental support centers and pediatric neurology clinics are often treated as a last resort, but early comprehensive assessment — building a full cognitive profile — improves the precision of support. A cognitive assessment like the WISC-V can reveal discrepancies between different cognitive domains and help identify multiple areas of difficulty simultaneously.
Prioritize adjusting the environment over demanding more effort
The most effective approach to preventing secondary disorders is not encouraging the child to try harder — it is removing the environmental conditions that generate repeated failure. Providing copies of board notes, extending test time, adjusting font sizes on worksheets — accommodations that look minor can interrupt the cycle of accumulated failure experiences that leads to secondary difficulties.
Summary
The overlap among LD, ADHD, and ASD is statistically frequent, not exceptional. Fitting a child into a single diagnostic framework risks leaving real difficulties invisible. Understanding the full picture of what the child is actually struggling with — rather than counting diagnoses — improves the quality of support.
Secondary disorders are preventable. Prevention requires early recognition of primary differences and adjustments to the environment. Before being startled by how many diagnoses there are, starting with "what is this child struggling with right now?" is the more useful question.
Related Articles
- 148 Specific Learning Disorder (SLD): An Overview — Dyslexia, dyscalculia, and dysgraphia: definitions, prevalence, and early identification
- 166 Reading the WISC-V and Communicating Findings to Schools — How to use a cognitive assessment to map the full picture of co-occurring difficulties
- 167 Special Education: System, Choices, and Reasonable Accommodations — Turning the insights from assessment into systemic environmental adjustments through the education system
References
- Rong Y, Yang CJ, Jin Y, Wang Y. Prevalence of attention-deficit/hyperactivity disorder in individuals with autism spectrum disorder: a meta-analysis. Res Autism Spectr Disord. 2021;83:101759. doi:10.1016/j.rasd.2021.101759
- Lichtenstein P, Carlström E, Råstam M, Gillberg C, Anckarsäter H. The genetics of autism spectrum disorders and related neuropsychiatric disorders in childhood. Am J Psychiatry. 2010;167(11):1357–1363. doi:10.1176/appi.ajp.2010.10020223. PMID: 20686187.
- Willcutt EG, Betjemann RS, McGrath LM, et al. Etiology and neuropsychology of comorbidity between RD and ADHD: the case for multiple-deficit models. Cortex. 2010;46(10):1345–1361. doi:10.1016/j.cortex.2010.06.009. PMID: 20663494.
- Mugnaini D, Lassi S, La Malfa G, Albertini G. Internalizing correlates of dyslexia. World J Pediatr. 2009;5(4):255–264. doi:10.1007/s12519-009-0049-7. PMID: 19911136.
- American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders, 5th ed. (DSM-5). Washington DC: APA; 2013. doi:10.1176/appi.books.9780890425596
- Pennington BF, McGrath LM, Peterson RL. Diagnosing Learning Disorders: From Science to Practice. 3rd ed. New York: Guilford Press; 2019.
- Mayes SD, Calhoun SL, Bixler EO, Zimmerman DN. IQ and neuropsychological predictors of academic achievement. Learn Individ Differ. 2009;19(2):238–241. doi:10.1016/j.lindif.2008.09.001