Is Dyslexia Genetic?

By Laura Lurns · Reviewed by Philip Weaver · Last reviewed 2026-10-01

Is dyslexia genetic?

The International Dyslexia Association (IDA) wrote a new definition in 2025. The definition describes trouble reading words or spelling, in accuracy, speed or both. It says the causes are complex. It names "genetic, neurobiological, and environmental influences" that act on each other as a child grows.

The definition names no single cause.

So the definition does name genetic influences. It names other influences too, and says they act on each other.

What two twin studies say

One twin study asked parents by phone about signs of dyslexia in their twins (Brimo and colleagues, 2021). There were 1,688 twins, all nine years old. The children were not tested. From the parents' answers, it estimated that genes account for part of the differences in those signs. That is a finding about many children. We could read only its summary.

One large twin study looked at dyslexia, dyscalculia and ADHD together (van Bergen and colleagues, 2025). It used Dutch twins and their brothers and sisters, tested at ages 7 and 10.

Each difficulty was set by a cut-off the study chose, not a diagnosis. In that study, a child with one was more likely than other children to have a second. Most had only one.

In that study, the genetic risks for the three partly overlapped. The study did not point to one of the three causing another. The authors name two limits. Twin studies rest on assumptions. And the tests may have been too far apart to see one cause another.

That is a finding about many children. The research we hold cannot say how much of one child's reading trouble comes from genes.

Genes are not a verdict

One paper describes the causes of conditions like dyslexia as "probabilistic and multifactorial" (Pennington, 2006). In that model, many things change the chances. No one thing decides alone. It is a model, not a study. We could read only its summary.

In our view, genes are not a verdict. They do not decide on their own what happens to your child.

Catts and colleagues (2026) write that "no behavioral, genetic, or neurological correlate, beyond difficulties in word-level literacy, shows consistency at the individual level that is necessary to reliably identify dyslexia."

By their account, nothing beyond the reading and spelling trouble reliably identifies dyslexia in one child. No scan or gene test does.

No study we hold can predict one child's dyslexia from family history.

No study we hold predicts how far one child's reading will go with teaching. A diagnosis describes where a child is today. It does not predict where they will be after a year of the right kind of practice.

What if others in your family had reading trouble?

In our view, your child's own reading tells you where to start. The family history is worth knowing too.

Has anyone else in your family had trouble with reading or learning? If so, say so when you ask for help.

If you see reading trouble, act on it. Our position is to put support in place now, not to wait and see. No study we have tests wait-and-see as a plan for a learning difficulty. So we would not tell you to wait.

You can start without a name.

Does it change what you do?

In our view, the cause mostly does not change the first step. That step is to work out which job of reading is going wrong. The exception is a skill that was there and has gone. Our position is that a lost skill goes to a doctor first, not a tutor.

Our rule is to describe patterns on these pages. We do not put a name on a child. We say a child "is developing reading skills."

When to ask for help

Each of these is a reason to ask for help on its own.

• Little change, even with steady practice and good teaching.
• Reading well below what school expects.
• A teacher who raises a concern about reading.
• Extreme upset about reading.
• Complete avoidance of reading.
• Hopelessness about learning.
• Sadness or worry that lasts.
• Significant delays in speech, language or motor development.
• A skill that was there and has gone. Our position is that a lost skill goes to a doctor first, not a tutor.

Start with the teacher. Say what you are seeing at home, and what you have tried. Beyond the teacher, the right person depends on what it turns out to be about. If the work is too hard, someone who works on that school skill. If worry or mood is the thing, someone who works with children's mental health. In our view, delays in speech, language or movement are worth raising with your child's doctor. In our view, if you are worried enough to ask, a professional evaluation is worth asking about.

Any talk of hurting themselves is a same-day call to your doctor or a crisis line.