Overlap of learning disabilities and ADHD

What percentage of children with Attention Deficit Hyperactivity Disorder (ADHD) also has learning problems? Previous studies reveal widely divergent estimates of the overlap of attention and learning disabilities. The results are confounded by differences in the studies’ definitions of LD, by their exclusion of some areas of learning such as written expression; and by other methodological flaws. Researchers Susan D. Mayes, Susan L. Calhoun, and Errin W. Crowell, Penn State University College of Medicine, sought to remedy these shortcomings in a new study. They evaluated 119 children ages 8 to 16 years who had been referred to a child diagnostic clinic.

In this study, Mayes et al. assessed two groups of children – those diagnosed with ADHD and those referred who did not meet the criteria for ADHD. Both groups of children were tested in basic reading, reading comprehension, math, spelling and written expression. Each child’s writing was scored for ideas and development, organization, vocabulary, sentence structure, grammar, capitalization and punctuation. The differences in the magnitude of the learning problems were studied by comparing children diagnosed with both ADHD and LD to those with ADHD but no LD, with LD but no ADHD and those without either LD or ADHD.

The children in this study were originally referred to the clinic because of learning, attention, mood and/or behavior problems. They underwent clinical evaluations by a child psychologist and a child psychiatrist or developmental pediatrician. School records and parent and teacher questionnaires were gathered on every child. Children with below-average IQ or with psychosis, autism/pervasive developmental disorder, bipolar disorder, significant hearing or visual loss or neurological impairment were excluded from the study. A second psychologist independently rescored all test data. A diagnosis of ADHD was based on criteria in the Diagnostic and Statistical Manual of Mental Disorders IV, and LD was defined as academic performance in a subject area that was significantly lower (< .05) than predicted by the child’s full-scale IQ.

Problems frequently co-exist

Approximately 72 percent of the children with learning disabilities also met the criteria for ADHD. Children with ADHD were not only more likely to have a learning disability; they were more likely to have a disability in more than one area and the disability was likely to be more severe than LD children without ADHD. About 27 percent of the children with ADHD had a disability in basic reading or reading comprehension. Approximately one third had disabilities in math and another third in spelling; however, nearly two-thirds demonstrated a disability in written expression.

Mayes et al. conclude that these results demonstrate the importance of evaluating such children for problems with written expression. They believe that when written expression is not evaluated, LD will be significantly underestimated, since twice as many children revealed problems in this area than in any other area. These results cast doubt on previous researchers’ reports that reading disabilities are the most common type of learning disability. Many of the screening tests used for LD do not include a measure of written expression. Given that 65 percent of these children with ADHD had a learning disability in written expression, it is concluded that it is important to assess written expression when evaluating a child for ADHD or LD.

Attention and learning problems are interrelated

Overall, these results indicate that attention and learning problems are interrelated and usually occur together. Children with attention problems are likely to have more than one learning problem, and these problems tend to be more severe than those found in children without attention problems. Mayes et al. state that educators should be aware that attention and learning problems exist on a continuum and are not simply present or absent, and that they usually occur together. These researchers point out that while the percentage of ADHD children found in their study is similar to what has been found at other clinics, these results are not applicable to the general population of children who have not been referred to a child diagnostic clinic. These results also indicate that when a child does not meet the diagnostic criteria for ADHD or LD, that child may still have some degree of attention or learning problems that interferes with his classroom performance. He/she may need help to achieve at grade level.

“Learning Disabilities and ADHD: Overlapping Spectrum Disorders” Journal of Learning Disabilities Volume 33, Number 5, October 2000 Pp. 417-424.

Published in ERN October 2000 Volume 13 Number 7

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