The New Definition of Dyslexia: What Changed, and Why SLPs Are Key to Catching It Early

For more than 20 years, the field worked from the same definition of dyslexia. In 2025, the International Dyslexia Association (IDA) updated it.

The new definition reflects decades of new science. It also puts something front and center that SLPs already know: early oral language weaknesses often foreshadow literacy challenges.

In our latest provider CE webinar, part of the Reaching Every Learner series with Sprout Labs, reading specialist and researcher MaryKate DeSantis and Sprout Labs Head of Literacy Eileen Catizone broke down what the new definition means. They covered what to listen for when a student reads and where SLPs fit in. Watch the full recording, or read on for what we learned.

What's New in the IDA Definition of Dyslexia

The updated definition still calls dyslexia a specific learning disability. It still centers on difficulty with word reading and spelling, in accuracy, speed, or both. But several shifts change how we think about it.

1. It exists on a continuum. This is the biggest change. Dyslexia isn't a yes-or-no category. It sits on a continuum of severity, so identification is about probability, not a fixed cutoff. As MaryKate put it, it's less like chicken pox and more like blood pressure. The definition also notes the difficulties persist "even with instruction that is effective for the individual's peers."

2. It looks different across languages. The new definition says difficulties "vary depending on the orthography." That accounts for the many writing systems students learn to read in.

3. The causes are complex. Genetic, neurobiological, and environmental influences all interact over time. MaryKate noted that research has now linked roughly 175 genes to dyslexia. Environment still matters too: health, poverty, and school-related anxiety can all shape how dyslexia shows up.

4. Phonology isn't the whole story. Phonological and morphological processing difficulties are common, but not universal.

5. Oral language is an early warning sign. Early oral language weaknesses often foreshadow literacy challenges. This is squarely in SLP territory.

6. The effects reach beyond reading. The definition now names secondary consequences: comprehension, less reading and writing practice, slower growth in vocabulary and knowledge, and effects on well-being and future employment.

7. Early support matters most. Identification and targeted instruction help at any age. But support before and during the early school years is "particularly effective."

The takeaway is hopeful. Dyslexia is multifactorial, and effective instruction reduces risk.

How Common Is Dyslexia?

Because dyslexia sits on a continuum, there's no single number. You'll see "1 in 5" and "1 in 13" cited, but neither is definitive. One figure the research consistently cites is about 7.1% worldwide. The real answer depends on the group of students and on each individual student.

Early Signs of Dyslexia to Watch For

Many early signs are observable, and many show up before a child ever sees print.

Before school (from about 18 months)

• Trouble learning nursery rhymes and songs
• Trouble remembering names or letter sounds, even after lots of practice
• Immature speech that lasts longer than expected
• A history of slow or delayed speech development
• A family history of language or learning difficulties

MaryKate stressed that family history is one of the strongest risk signals. She'd like to see asking about it become as routine in schools as it is in medicine.

Once school starts

• Difficulty with letter-sound correspondence
• Trouble blending sounds that were each said correctly (sounding out c-a-t, then saying "dat")
• Weak letter knowledge, including trouble recognizing their own name in print
• Leaning on pictures to guess words instead of decoding
• Avoiding reading, either by withdrawing or by acting out (one student always needed the bathroom when it was time to read aloud)
• Slow, effortful reading, which means less reading and less exposure over time
• Difficulty with language-heavy tasks like reading or listening, then writing or discussing

What You Can Hear in Under a Minute of Reading

Eileen and MaryKate played three short, anonymized clips of students reading. Attendees used a checklist of observable reading behaviors to note what they heard. A few sentences revealed a lot.

• A sixth grader reading simple decodable text. She knew her letters and sounds but wasn't automatic yet. She stalled on familiar words and didn't know the word "gulls," so she couldn't use meaning to help her decode it. Her reading was accurate in places but laborious, and limited vocabulary played a big role.
• A second grader reading single words. He added a schwa after the first consonant ("suh-it" for "sit"). He moved sounds around ("swish" for "wish") and mixed up short and long vowel patterns. Reading words in isolation showed exactly where to start.
• A third grader reading a short passage. She sounded mostly fluent but read word by word, not sentence by sentence. Missing small words threw off the next ones, and she guessed at unfamiliar words like "common." The lesson: this student needs a bigger sample and a closer diagnostic look. No single snippet, or single test, tells the whole story.

Writing samples are just as revealing. One third grader with a strong spoken vocabulary wrote "boo-boo" in a story. It wasn't immaturity. He picked a word he knew he could spell. That's a compensation strategy, and it's easy to miss.

Myth: Letter Reversals Mean Dyslexia

Mixing up b, d, p, and q before third grade is usually developmental, not a sign of dyslexia. Dyslexia is language-based, not visual. Reversals that continue in older students are worth a look, but often they reflect limited reading exposure.

Dyslexia and DLD Often Go Together

Dyslexia frequently co-occurs with other conditions, especially developmental language disorder (DLD). That overlap can make it harder to tell which need is primary, and it makes treatment more complex. It's also why an SLP's eye for early oral language difficulties is so valuable.

How SLPs Can Support Students with Dyslexia

SLPs bring deep knowledge of how language is built. Identifying, and in many settings treating, dyslexia is within the SLP scope of practice. That doesn't mean replacing the reading specialist. It means working together.

Many SLPs already do work that supports reading:

• Explicit, systematic teaching that moves from simple to complex
• Direct teaching of sound-symbol correspondence, pairing phonological work with letters
• Building vocabulary, syntax, story grammar, and narrative skills, which matter more as students get older
• Spotting early risk signs and sharing them with teachers, families, and interventionists
• Showing families how speech-language goals connect to literacy at home

Eileen added that reading specialists have spent recent years learning phonological awareness, which was traditionally SLP territory. The two roles overlap more every year. When they collaborate, both work smarter, not harder. Looking for goal ideas? See our SLP IEP goals guide and goal bank.

Carrying Practice Home with Sprout Labs

Eileen named a problem every reading specialist and SLP knows. You teach a skill, send home practice pages, and the practice never happens. Students get better with more practice, so that gap matters.

That's why Sprout Labs built Sprout's Reading World with SLPs and reading specialists in mind. It follows a phonics scope and sequence while also building oral language, vocabulary, and comprehension. Lessons are multimodal and visual, which helps students with language delays. Students review what they learned last session, then practice at the word level, the sentence level, and finally in a connected story.

It's one more way SLPs and reading specialists can work toward the same goal. Learn more at sproutlabs.com →

About Our Speakers

MaryKate DeSantis is a Doctoral Fellow in Educational Psychology at the University of Connecticut's Neag School of Education and teaches at Boston College. She has worked as a special educator, reading specialist, district literacy coach, and clinician at Boston Children's Hospital. She is the founder of Left Side Strong LLC.

Eileen Catizone, M.Ed., is Head of Literacy at Sprout Labs and an Orton-Gillingham and IDA Dyslexia Practitioner. A reading specialist, curriculum developer, and PD leader, she has taught PreK through 8th grade and still works with students with dyslexia.

Karin Hartunian-Koukeyan, MS, CCC-SLP, moderated the session. She is a Continuing Education Consultant at Parallel, founder of SpeechFit, and has provided telepractice since 2010.

See the full Reaching Every Learner series →

Frequently Asked Questions About Dyslexia

What is the new IDA definition of dyslexia?

The 2025 update describes dyslexia as a specific learning disability that affects word reading and/or spelling accuracy, speed, or both. It sits on a continuum of severity and persists even with instruction that works for peers. It also names complex genetic, neurobiological, and environmental causes, and the value of early support.

Is dyslexia a spectrum, like autism?

In one sense, yes. The new definition treats dyslexia as a continuum rather than a fixed set of traits or a single cutoff score.

How do you tell dyslexia apart from a lack of good instruction?

Look at risk factors and at how the student responds to instruction. First ask how the student is being taught, and whether that approach is evidence-aligned. Don't wait for a student to fail. Screen early and act on risk.

What helps older students with dyslexia?

It's never too late. For middle and high schoolers, add morphology, word meaning, syntax, and comprehension work, using age-appropriate text. Strengthening phonemic awareness can still help older readers build foundational skills.

Should students memorize high-frequency words?

Flashcard-style memorization doesn't support orthographic mapping. Instead, point out the parts of each word that follow regular sound-letter patterns. In "said," the s and d are regular. Only the vowel spelling has to be learned by heart.

What tools can SLPs use to screen for dyslexia risk?

Start with a phonics survey of words in isolation, or letter-sound checks for younger students. DIBELS and Acadience are freely available but require training. Orton-Gillingham certification is a deeper path for intervention.

Keep Learning with Parallel and Sprout Labs

Missed it live? Watch the full recording on YouTube. This session was part of Parallel's free professional development series for providers. Watch for the next session in the Reaching Every Learner series with Sprout Labs, and explore more literacy resources at sproutlabs.com.

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