What to Know About Dyslexia’s Comorbidities

Monday, October 24, 2022

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.

Co-occurring condition	Similarities	Differences	Questions to consider
ADHD	Difficulties with fluency, accuracy, and comprehension Avoidance of reading	Students with ADHD may not have trouble with word reading but may skip words or punctuation. Attention may affect comprehension.	When ADHD symptoms are treated, is the student better able to read words and learn reading skills?
Autism	Difficulties with comprehension For some, language impairment	Autism is not usually associated with word reading difficulties.	Is there an underlying language impairment? Does the student have difficulty decoding words and nonsense words? Does the student work extra hard to read accurately? (Hendren et al., 2018)
Behavior disorders (ODD, CD)	Attention difficulties, anxiety, task avoidance, reading difficulties in grades 3 and up—especially accuracy (Castro et al., 2020)	Difficulties in other academic areas may be present for students with ODD, CD.	Do behavior difficulties occur primarily when academic or reading tasks are happening? Did behavior difficulties begin before school age?
Other learning disorders	Dyslexia & dyscalculia: Difficulties with visual working memory and task shifting, anxiety, lower self-esteem, distraction, or attention difficulties Dyslexia & dysgraphia: Difficulties with spelling, orthographic awareness, and rapid automatized naming (Chung et al., 2020)	Phonological processing, rapid naming of numbers and letters, reading tasks, and processing speed do not appear to be affected in students with dyscalculia alone (Haberstroh et al., 2019).	Has the student received evidence-based instruction in the specific area of deficit? Which specific skills present difficulties for the student? Does the student have mild motor differences, which may link dysgraphia and dyslexia?
DLD/SLI	Difficulties with phonological awareness and naming-speed tasks (Snowling et al., 2019)	Students with DLD/SLI tend to do better on measures of orthographic processing, reading, semantics, and phonological memory than students with reading disorders alone (Spanoudis et al., 2019).	Can the student recognize orthographic patterns? This skill is not impaired in DLD/SLI alone. Are auditory perception, verbal working memory, or processing speed impaired? Deficits could indicate DLD/SLI. Are executive or motor issues also involved in preschool students? Deficits could point to DLD/SLI (Spanoudis et al., 2019).
Anxiety	Difficulties with working memory, slower reading rate, less motivation to read, avoidance of reading tasks (Katzir et al., 2018), and comprehension problems (Macdonald et al., 2021)	Anxiety does not appear to affect untimed word-reading accuracy (Macdonald et al., 2021).	Are fatigue or loss of sleep affecting a student’s functioning? Do anxiety interventions improve any reading skills? Does the student experience anxiety only when asked to read?

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

Research and Resources:

Ashraf, F., & Najam, N. (2020). An epidemiological study of prevalence and comorbidity of non-clinical dyslexia, dysgraphia and dyscalculia symptoms in public and private schools of Pakistan. Pakistan Journal of Medical Sciences, 36(7), 1659–1663. https://doi.org/10.12669/pjms.36.7.2486

Castro, E., Cotov, M., Brovedani, P., Coppola, G., Meoni, T., Papini, M., Terlizzi, T., Vernucci, C., Pecini, C., & Muratori, P. (2020). Associations between learning and behavioral difficulties in second-grade children. Children, 7(9), 112. https://doi.org/10.3390/children7090112

Chung, P. J., Patel, D. R., & Nizami, I. (2020). Disorder of written expression and dysgraphia: Definition, diagnosis, and management. Translational Pediatrics, 9(Suppl 1), S46–S54. https://doi.org/10.21037/tp.2019.11.01

Darweesh, A. M., Elserogy, Y. M., Khalifa, H., Gabra, R. H. & El-Ghafour, M. A. (2020). Psychiatric comorbidity among children and adolescents with dyslexia. Middle East Current Psychiatry 27, 28. https://doi.org/10.1186/s43045-020-00035-y

Haberstroh, S., & Schulte-Körne, G. (2019). The diagnosis and treatment of dyscalculia. Deutsches Arzteblatt International, 116(7), 107–114. https://doi.org/10.3238/arztebl.2019.0107

Hendren, R. L., Haft, S. L., Black, J. M., White, N. C., & Hoeft, F. (2018). Recognizing psychiatric comorbidity with reading disorders. Frontiers in Psychiatry, 9, 101. https://doi.org/10.3389/fpsyt.2018.00101

Herman, R., Kyle, F., & Roy, P. (2019). Literacy and phonological skills in oral deaf children and hearing children with a history of dyslexia. Reading Research Quarterly, 54(4), 553–575. https://doi.org/10.1002/rrq.244

International Dyslexia Association. (2020). Attention-deficit/hyperactivity disorder and dyslexia. https://dyslexiaida.org/attention-deficithyperactivity-disorder-adhd-and-dyslexia/

Katzir, T., Kim, Y. G., & Dotan, S. (2018). Reading self-concept and reading anxiety in second grade children: The roles of word reading, emergent literacy skills, working memory and gender. Frontiers in Psychology, 9, 1180. https://doi.org/10.3389/fpsyg.2018.01180

Macdonald, K. T., Cirino, P. T., Miciak, J., & Grills, A. E. (2021). The role of reading anxiety among struggling readers in fourth and fifth grade. Reading & Writing Quarterly, 37(4), 382–394. https://doi.org/10.1080/10573569.2021.1874580

McGrath, L. M., & Stoodley, C. J. (2019). Are there shared neural correlates between dyslexia and ADHD? A meta-analysis of voxel-based morphometry studies. Journal of Neurodevelopmental Disorders, 11(1), 31. https://doi.org/10.1186/s11689-019-9287-8

Moll, K., Snowling, M. J., & Hulme, C., (2020). Introduction to the Special Issue “Comorbidities between reading disorders and other developmental disorders.” Scientific Studies of Reading, 24:1, 1–6, DOI: 10.1080/10888438.2019.1702045

Snowling, M. J., Nash, H. M., Gooch, D. C., Hayiou-Thomas, M. E., Hulme, C., & Wellcome Language and Reading Project Team (2019). Developmental outcomes for children at high risk of dyslexia and children with developmental language disorder. Child Development, 90(5), e548–e564. https://doi.org/10.1111/cdev.13216

Spanoudis, G. C., Papadopoulos, T. C., & Spyrou, S. (2019). Specific language impairment and reading disability: Categorical distinction or continuum? Journal of Learning Disabilities, 52(1), 3–14. https://doi.org/10.1177/0022219418775111

Vanova, M., Aldridge-Waddon, L., Jennings, B., Puzzo, I., & Kumari, V. (2021). Reading skills deficits in people with mental illness: A systematic review and meta-analysis. European Psychiatry, 64(1), E19. doi:10.1192/j.eurpsy.2020.98

Visser, L., Kalmar, J., Linkersdörfer, J., Görgen, R., Rothe, J., Hasselhorn, M., & Schulte-Körne, G. (2020). Comorbidities between specific learning disorders and psychopathology in elementary school children in Germany. Frontiers in Psychiatry, 11, 292. https://doi.org/10.3389/fpsyt.2020.00292

Willcutt, E. G., McGrath, L. M., Pennington, B. F., Keenan, J. M., DeFries, J. C., Olson, R. K., & Wadsworth, S. J. (2019). Understanding comorbidity between specific learning disabilities. New Directions for Child and Adolescent Development, 165, 91–109. https://doi.org/10.1002/cad.20291

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