What to Know About Dyslexia’s Comorbidities

Identifying dyslexia can be more complicated when other health or developmental conditions are also present. As an educator or clinician, you’re asked to find out if a reading difficulty is the result of dyslexia or some other condition that changes how the brain works. For example, is a student feeling anxiety because reading is so hard, or is anxiety keeping a student from reading with ease? 

This article may help you map the shared territory, differentiating factors, and key questions to ask as you make your way through a comprehensive dyslexia evaluation. 

What Makes a Dyslexia Comorbidity So Common 

Roughly 60% of those with dyslexia have at least one other diagnosis (Darweesh et al., 2020). Researchers have found that conditions co-occur because of the specific way biological, environmental, and protective factors interact in people’s bodies and in their lives (Moll et al., 2020).   

Here are some ideas to bear in mind: 

• A single risk factor, such as family income level or genetic differences, may lead to deficits in different areas.  
• Symptoms from multiple conditions can overlap. For example, problems with working memory are linked to both ADHD and dyslexia.  
• Conditions can develop independently of each other or one condition may develop as a result of another.
• When people have more than one condition at the same time, the effects of each condition tend to be more severe (Willcutt et al., 2020).  

What Are the Most Common Dyslexia Comorbidities?  

Here’s a brief overview of the conditions most commonly associated with reading disorders like dyslexia.  

Attention-deficit/hyperactivity disorder (ADHD)  

ADHD is the most common neurodevelopmental condition to occur alongside dyslexia. Between 25% and 40% of those with one condition also have the other (McGrath & Stoodley, 2019).  

Other specific learning disorders (SLDs) 

In studies, between 30% and 47% of those with dyslexia also have dysgraphia symptoms (Chung et al., 2020). Around 26% of those with dyslexia have symptoms of dyscalculia. Dysgraphia and dyscalculia can also occur together—around 36% of the time (Ashraf & Najam, 2020).  

Developmental language disorder (DLD) or specific language impairment (SLI)  

A 2019 study published in Child Development found that 43% of 8-year-old children with DLD also had dyslexia and 58% of children with dyslexia had DLD. With DLD/SLI, phonological difficulties may improve over time, but comprehension problems might continue.  

Learn more about how sex and gender can influence diagnosis of DLD.

Anxiety 

Studies show that around 21% of students with SLDs also have anxiety disorder (Visser et al., 2020). Researchers think there is a two-way relationship between anxiety and dyslexia.  

When students are anxious, brain functions such as processing speed, visual attention, and task-switching abilities don’t work as well. That’s why a person with an anxiety disorder may develop reading difficulties. It’s also true that students who are having reading difficulties become anxious when they’re asked to read.  

Oppositional defiant disorder (ODD) or conduct disorder (CD) 

For some people, behavior disorders make it harder to learn to read. For others, reading difficulties can eventually lead to behavior problems. An accurate picture can be hard to piece together, especially if symptoms of ADHD are also present (Hendren et al., 2018).   

Autism 

Researchers estimate that autism and reading disorders overlap 6%–30% of the time. It’s important to note that when autistic students have difficulty with reading comprehension, it is not usually related to decoding problems (Hendren et al., 2018).   

Explore the WPS Guide to Autism Assessments and Resources.

Disabilities 

When someone has a disability, its characteristics may affect the ability to read. For example, in one recent study, researchers found similar difficulties with word reading, non-word reading, and spelling among deaf students and students with dyslexia (Herman et al., 2019). Similarly, studies have shown that schizophrenia affects phonological processing, reading rate, vocabulary, working memory, and word reading (Vanova et al., 2020).   

It’s important to understand as much as possible about someone’s background and their daily functioning so you can separate the effects of a disability from the construct you’re measuring. 

Are Your Assessments Equitable for People with Disabilities? Learn more here.

What to Consider in an Assessment 

Here are a few ways to differentiate between dyslexia and other common conditions.  

Other key questions: 

• When did reading difficulties begin?  
• Do symptoms stay the same across different settings and contexts? 
• Do dyslexia symptoms change when the other condition is treated? 
• If a student has a psychological or physical disability, does it affect skills related to reading or taking assessments?

Key Messages 

It can take time, experience, and a keen eye to discern between dyslexia and commonly co-occurring conditions. When you’re clear about dyslexia comorbidity, you’ll be better able to work with the student, their family, and your team to focus and prioritize interventions. 

Download the WPS Dyslexia Assessment Tool Kit. 

DYSLEXIA RESOURCES 

Further Reading on Dyslexia  

• Challenges in Testing for Dyslexia 
• Are Your Dyslexia Assessments Falling Short? 
• Discover the Most Effective Way to Identify Dyslexia 
• How Do You Choose the Right Dyslexia Assessment for Your Student? 
• Is Pandemic Fallout Still Affecting Assessments? 
• Six Key Messages from NASP’s Position Statement on Identifying SLDs 
• How to Assess the Five Components of Reading This School Year 
• How to choose the best Dyslexia assessments for your students 
   

Check Out our Dyslexia Webinars 

• Best Practices in Dyslexia Assessment  
• Dyslexia 101: Understanding Dyslexia and Its Impact on Reading, Spelling, and Self-Esteem 
• Challenges in Assessing Dyslexia
• Introduction to the Tests of Dyslexia (TOD™) 

 
Check out our Dyslexia Assessment Toolkit  

https://www.wpspublish.com/dyslexia-assessment-tool-kit 

Do you have questions? Check out our Dyslexia FAQs 

• Tests of Dyslexia (TOD™) 
• Dyslexia Assessment Challenges
• Dyslexia Intervention  
• Dyslexia Assessment Best Practice