Published by Unseen Progress, an independent publisher of caregiver research. Last reviewed 2026-07-28. Part of the learning disability research overview.
Short answer. Dyslexia and ADHD both produce reading difficulty, but they break reading at different points. Dyslexia is a phonological-processing difference that makes decoding — turning letters into sounds — inaccurate and effortful. ADHD is an attention and working-memory difference that leaves decoding intact but degrades stamina and comprehension. They co-occur far more often than chance: roughly 25–40% of children with one meet criteria for the other (Willcutt & Pennington, 2000). The practical consequence is that treating one does not treat the other, and a child who has both needs both addressed.
Reading is not one skill. It is at minimum two: recognising the words on the page, and holding onto meaning across sentences. Dyslexia and ADHD attack different halves.
Dyslexia is defined by the International Dyslexia Association as a difficulty with accurate and fluent word recognition, arising from a deficit in the phonological component of language. The child's difficulty is at the level of the word itself. Sounding out sp-l-in-t is slow and error-prone no matter how hard they concentrate. Effort does not close the gap, because the system that maps sounds to letters is the system that works differently (Shaywitz, 2003; Peterson & Pennington, 2012).
ADHD leaves word recognition largely intact. A child with ADHD and no dyslexia can usually decode accurately when you sit with them and hold their attention on a single line. What breaks is everything that requires sustained engagement across time: keeping the thread of a paragraph, remembering what happened three pages ago, noticing that a sentence stopped making sense, finishing the chapter at all. The difficulty is in executive function and working memory rather than in phonology (Barkley, 2014).
The clearest discriminator is what happens under ideal conditions. Sit with the child, remove distraction, give them a short unfamiliar passage, and ask them to read it aloud.
Two more patterns are worth noticing. Dyslexic difficulty is markedly worse with nonsense words — invented words like blorp or strempt that cannot be recognised by sight or guessed from context. This is why nonsense-word fluency appears on nearly every dyslexia screener; it isolates decoding from everything else. And dyslexic difficulty tends to be strikingly specific: a child who cannot read a paragraph may have a large spoken vocabulary and sophisticated reasoning. ADHD-related difficulty is usually more diffuse, showing up in maths, homework routines, and instructions as well.
The co-occurrence is not coincidence and not diagnostic sloppiness. Willcutt and Pennington's work established comorbidity rates in the 25–40% range, well above what independent conditions would produce. Pennington's multiple deficit model (2006) explains why: complex cognitive conditions are not caused by one gene or one deficit but by several partly-overlapping risk factors, and some of those factors — notably processing speed — contribute to both conditions. Shared risk produces shared outcomes.
For families this has a specific and often costly implication. A child diagnosed with one condition is frequently not assessed for the other, because the first diagnosis appears to explain the difficulty. The reading problem is attributed entirely to inattention, or entirely to dyslexia, and the untreated half continues to cause failure that then gets read as non-compliance or low effort.
If your child has an ADHD diagnosis and reading is still disproportionately hard after attention is genuinely being managed, that is a reason to request a dyslexia evaluation, not a reason to conclude the ADHD treatment is failing. The reverse holds too: a dyslexic child receiving good structured literacy who still cannot finish work, follow multi-step instructions, or sustain effort across a task deserves an ADHD assessment.
This is the single most consequential misunderstanding in this area. Stimulant medication reliably improves attention, on-task behaviour, and often reading stamina — a child who could not sit through a chapter can now sit through it. What it does not do is improve phonological processing. Decoding accuracy is essentially unchanged. Parents sometimes read the improvement in stamina as evidence that the reading problem is solved and stop pursuing reading intervention, and the decoding gap continues widening.
Dyslexia needs explicit, systematic, cumulative structured literacy — Orton-Gillingham, Wilson, Lindamood-Bell — at a dose the classroom usually cannot supply. See structured literacy vs whole language for what the evidence actually says. ADHD needs behavioural parent training, classroom supports, and often medication. Neither substitutes for the other. A child with both who receives only one intervention will show partial improvement that plateaus, which is frequently misread as the child having reached their ceiling.
1. Run the read-aloud test above with an unfamiliar passage, in a quiet room, when the child is not tired. Note specifically whether errors are decoding errors or attention errors. 2. Ask any evaluator directly: "Did you assess phonological processing, and did you assess attention?" A comprehensive evaluation covers both. Many do not, and the report will not say so. 3. If your child is medicated for ADHD, evaluate reading on a medicated day. If decoding accuracy is still weak with attention handled, that points at dyslexia. 4. Track decoding accuracy and comprehension as two separate measures over a 90-day window. They can move independently, and an average hides that. This is exactly the pattern that memory is bad at holding — improvement in one alongside a plateau in the other reads, from the inside, as "nothing is working."
The two conditions look similar from the outside because the visible outcome — a child who cannot read the way their classmates do — is the same. The mechanisms are not the same, and the interventions are not interchangeable.
---
Unseen Progress publishes long-form caregiver research and builds research-backed daily trackers for the families covered. See the full learning disability research overview for the complete framework.