"...One of the key issues in reading disorder is the co-occurrence or comorbidity of reading disorder with attention deficit hyperactivity disorder (ADHD). Rates of RD are elevated in ADHD emphasizing the need for comprehensive neuropsychological assessment of children and adults with ADHD.
Yoshimasu and colleagues published a free access study of the prevalence rates for RD in a population-based cohort of children and adolescents in Rochester, Minnesota.
The researchers in this study used analysis of multiple school and academic records to estimate the prevalence of reading disorder in a cohort of 5718 children. Reading disability was assessed by comparing measures of IQ and reading achievement. Using several validated formulas, reading disability can be assigned with reading achievement falls significant below what would be expected based on individual intelligence. Additionally, ADHD was estimated in the cohort using assessment of DSM-IV criteria, ADHD questionnaire results and evidence by records of a clinical diagnosis of ADHD.
The key findings from this epidemiologic study included:
508 cases of reading disability were indentified in the cohort
379 cases of ADHD were identified and as expected 75% of ADHD cases occurred in boys
For those without ADHD, the estimated rates for reading disorder were 14.5% for boys and 7.7% for girls
Rates for reading disorder were markedly elevated for children with ADHD with estimates of the prevalence of RD in boys with ADHD at 51.0% and for girls with ADHD 46.7%
A key finding from the study is the effect of a diagnosis of ADHD in girls on rates of RD. Female gender is a relative protective factor for RD, but once the diagnosis of ADHD is present, this protective effect is lost....