What Is It?

Dyslexia is a learning disability that makes reading difficult for children and adults who otherwise have the intelligence and motivation necessary to learn to read. Although people with dyslexia have trouble understanding words they read, they usually can understand the same words when they are read aloud by another person.

Researchers don’t know exactly what causes dyslexia, but they think there may be a problem during development that affects the way the brain processes information. They also believe that genetics (inheritance) plays a part. Although a gene for dyslexia has not been found, dyslexia does tend to run in families. Dyslexia is not caused by a physical disability, such as vision or hearing problems. Many people with dyslexia have average or above-average intelligence.

Dyslexia is the most common learning disorder. In the United States, approximately 5 percent to 10 percent of the population probably has some level of dyslexia.


A person with dyslexia may have difficulty with the following tasks:

  • Identifying words
  • Recognizing the sounds that make up words
  • Understanding and remembering what is read
  • Translating printed words into spoken words
  • Spelling
  • Organizing or sequencing thoughts
  • Rhyming words
  • Learning the alphabet and numbers during preschool and kindergarten

Some people with dyslexia tend to reverse or misread letters or words. For example, they may mistake the letter “b” for “d” or read the number “6” as “9.” They may read the word “was” as “saw” or may switch the order of words in a sentence. For example, they may read “are there” instead of “there are.” They also may see words as having incorrect spacing — either with odd spacing or no spacing at all.

Because of these difficulties, a person with dyslexia usually reads slowly and may hesitate often.

Dyslexia is not a vision problem. The eyes do not actually see words incorrectly, but the brain apparently has difficulty processing the visual information.

It is important to note that many young children reverse letters and numbers, misread words or misunderstand words as a normal part of learning to read. Children with dyslexia, however, continue to do so after their peers have stopped, usually by first or second grade. Dyslexia may not be recognized until a child starts school, when a student of normal intelligence begins to lag behind his or her peers in academic performance.


Your doctor will ask about your child’s medical, developmental and family histories and will examine him or her to check for possible physical causes that could make reading difficult, such as hearing or vision problems. He or she also will look for signs of other problems that could be causing your child’s reading difficulties. These could include motor-coordination disorders, attention-deficit hyperactivity disorder (ADHD), depression, anxiety and thyroid disorders. If no physical causes are found, the doctor may refer your child to a learning specialist for evaluation. Testing for learning disabilities often is done by psychologists or education specialists at schools or hospitals.

There is no single test to diagnose dyslexia. A number of standardized tests are used to evaluate a child’s intelligence, language, behavior and academic skills.

Expected Duration

With early diagnosis and appropriate treatment, many people with dyslexia go on to succeed both academically and professionally. However, dyslexia is a lifelong condition, not a temporary developmental delay.


There is no known way to prevent dyslexia. However, because the neurological problems that cause dyslexia may be related to prenatal factors, it is wise to follow the usual recommendations for a healthy pregnancy, such as eating a balanced diet and avoiding cigarettes, alcohol and drugs (unless approved by your physician). Scientists are exploring possible connections between learning disabilities and exposure to environmental toxins and pollutants.


Several techniques and strategies are used to help people with dyslexia, such as taping lectures, listening to books on tape, using flash cards and using computers to check spelling and grammar. It is best if information is presented in small units, a little at a time, and repeated over and over. In addition, using several senses (hearing, seeing and touching) can help the child make connections in order to increase learning. For example, a child might listen to a word, and then say the word while tracing the word’s shape with a finger. The child also could practice making sounds in front of a mirror, watching the shapes that his or her mouth makes.

Treatment may involve time spent with speech and language therapists, tutors and special-education teachers. With support, most children with dyslexia are able to make adjustments to their learning and remain in a regular classroom. Occasionally, some may require a special-education environment.

When To Call A Professional

Call your doctor if your child is lagging significantly behind his or her peers in reading or writing skills, particularly if there is a family history of dyslexia or another learning disorder.


Most children with dyslexia can do well academically and professionally. The outlook for each child depends on several factors, including the severity of the disability, when it is diagnosed, and the type and quality of treatment.

Johns Hopkins patient information

Last revised:

Diseases and Conditions Center

  A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.