ADHD and Dyslexia

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By Liji Thomas, MDReviewed by Jonas Wilson, MD, Ing. Med.

Attention deficit hyperactivity disorder is a neurodevelopmental condition that begins in childhood and often persists into adulthood. It is characterized by inattention, impulsivity and hyperactivity. It leads to a wide range of occupational, social, and executive impairments, through a spectrum of severity.

The symptoms include easy distractibility, incessant movement even when inappropriate, difficulty in finishing tasks that require sustained concentration or stillness, and impulsive behavior.

These children may also have other co-morbid disorders, such as anxiety or depression. Another well-known co-morbidity is dyslexia. This manifests as learning disabilities of various kinds, and often presents late.

There are various types of dyslexia, including difficulty with reading, speaking or writing.

Dyslexic individuals have a lot of trouble distinguishing letters, discriminating sounds, or just seeing a sentence as a line of intelligible words rather than un-understandable groups of unpronounceable letters.

It is known that these reflect weaknesses in the speech and auditory processing apparatus, working memory, and visual processing skills, but very good verbal reasoning capabilities. These may persist throughout life and require learning many new techniques to acquire data correctly.

ADHD and reading disability are often found to occur together in the same individual in about one-fifth of patients.

They show a characteristic outcome upon neuropsychological testing that reflects deficits in various cognitive functions.

These impairments have a synergistic effect in that one contributes to the worsening of other deficits.

Thus, children with ADHD who also have dyslexia may have more serious defects with cognitive processes, and poorer academic outcomes, as well as more significantly impaired behaviors.

Diagnosis and Treatment

Testing of various functions is required, which includes reading and language skills, executive functions and processing speed.

Significant deficits in verbal working memory, response inhibition, and processing speed accompany severely impaired component reading and language skills in children with dyslexia.

However, ADHD children typically show grossly weakened response inhibition and processing speed, but they also had somewhat weak reading and verbal working memory skills.

The combination of both showed deficits in both these groups of skills, which seemed to relate the disorders.

It is significant that all three groups had slower-than-normal processing speed, a finding which may suggest a common genetic susceptibility to this duo of conditions.

Another study, which used lexical processing and rapid naming to distinguish these two disorders, concluded that they may overlap significantly in lexical processing and the sublexical route processing.

However, children with only reading disabilities showed greater delay in rapid naming which may suggest that such conditions cause specific impairments in this area.

Discriminating between these conditions may be crucial in determining the individual’s capacity to pursue certain avenues of education or work subject to special recommendations to facilitate success in these careers.

The concurrent use of stimulants such as methylphenidate with appropriate neuropsychological therapy such as cognitive behavioral therapy needs further careful study to formulate an acceptable plan of action in these cases.

Treatment of the combined condition requires correction of both types of deficits in neurobehavioral development to ensure that the individual enjoys the optimal level of social, occupational and relational ease.