Writing in Pediatrics, Professor Kouichi Yoshimasu and colleagues reported that the chances of children and youths having reading disabilities is significantly higher among those who have ADHD than it is among the general population of children and youths. Furthermore, although boys are significantly more likely than girls to manifest reading disabilities among the general population, among children and youths with ADHD the chances of reading disabilities are about equal. However, because girls are so much less likely to have reading problems than boys, girls’ risk is much higher in relation to their female peers’ risk.
This is an especially valuable study, because it follows a large and representative sample of children over an extended period of time. Some readers may say, “So what?” to the outcome (“We already knew that there was a relationship between ADHD and reading problems,” they might continue), but this study helps to refine the knowledge and clarify the relationships. Many previous studies have used less trustworthy technical procedures, yielding data that are not as precise as those provided by Professor Yoshimasu and colleagues. What is more, as the authors suggested in their own conclusions, their results underscore the importance of routinely assessing the reading (and other educational functioning) of children who are examined for ADHD.
One of the short-comings of this study, acknowledged by the research team, is that the nature of the research design does not admit to analyses of causal relationships between ADHD and reading problems. Because these authors worked backwards across time, they simply can’t say which emerged before the other. It’s up to another group of researchers to take off from this study and conduct the prospective longitudinal study that will help scientifically disentangle the causal relationships.
Yoshimasu, K., Barbaresi, W. J., Colligan, R. C., Killian, J. M., Voigt, R. G., Weaver, A. L., & Katusic, S. K. (2010). Gender, Attention-Deficit/Hyperactivity Disorder, and reading disability in a population-based birth cohort. Pediatrics, 126, e788–e795.doi:10.1542/peds.2010-1187
OBJECTIVE: To determine the incidence of reading disability (RD) among children with and without research-identified attention-deficit/hyperactivity disorder (ADHD), separately according to gender, in a population-based birth cohort.
METHOD: Subjects included all children born in 1976–1982 remaining in Rochester, Minnesota, after 5 years of age (n = 5718). Information from medical, school, and private tutorial records was abstracted. Cumulative incidence of RD, by any of 3 RD formulas, in children with and without ADHD and corresponding hazard ratios (HRs) were calculated separately according to gender.
RESULTS: Cumulative incidence of RD by the age of 19 years was significantly higher in children with ADHD (51% in boys, 46.7% in girls) compared with those without ADHD (14.5% in boys, 7.7% in girls). Among children with ADHD, the risk for RD was similar in boys versus girls (HR: 1.0). However, among children without ADHD, boys were 2.0 times more likely than girls to meet RD criteria. Among girls, the HR for the risk for RD associated with ADHD (versus those without ADHD) was 8.1 (95% confidence interval: 5.7–11.5), which was significantly higher than the corresponding HR among boys (3.9 [95% confidence interval: 3.2– 4.9]).
CONCLUSIONS: The risk for RD is significantly greater among children with ADHD compared with those without ADHD. Among children with ADHD, the risk for RD is the same for boys and girls. However, among children without ADHD, boys are more at risk for RD than girls. Among girls, the magnitude of increased risk for RD associated with ADHD is nearly twice that among boys, because girls without ADHD are less likely to have RD than boys without ADHD.