Genetic Links Between Hyperactivity and Academic Achievement
29 May, 2007 07:29 pm
Hyperactive behavioral problems consisting of overactivity, impulsivity and inattentiveness are often associated with academic under achievement such that children who display more hyperactive/inattentive behavior problems tend to perform more poorly in math, reading, language and global measures of academic achievement. These associations remain even when intelligence and family demographics are taken into account
The extent to which common genetic and environmental factors operate across hyperactivity and achievement was explored in a large community sample of nearly two thousand 7-year-old twin pairs participating in the Twins Early Development Study (TEDS). TEDS is an ongoing population-based study whose sampling frame includes all twins born in England and Wales in 1994, 1995 and 1996. Both parents and teachers provided ratings of twins’ hyperactive behavior problems (e.g., restlessness, fidgeting, distractibility, impulsivity, and attention span). Academic achievement was based on teacher assessments of English and mathematics skills conducted at the end of the first year of primary school (equivalent to Grade 1 in the US). A measure of general cognitive ability was also included to allow us to control for the effects of intelligence on the association between hyperactivity and achievement. That is, to ensure that the link between hyperactivity and academic outcome was not simply a result of the association between hyperactivity and intelligence.
Approximately 40 to 50% of the genetic effects on hyperactivity were found to overlap with those on academic achievement. Moreover, it was these overlapping genetic effects that result in the relation between the two behaviors (i.e., genetic factors explained over 80% of the correlation between the hyperactivity and achievement). In other words, the reason why hyperactivity and academic achievement are related is almost entirely due to common genetic influences. The results were similar for both parent and teacher ratings of hyperactivity, for males and females, and for twin pairs in who were in the same and different classrooms. Because academic achievement scores controlled for general cognitive ability, the genetic association between hyperactivity and achievement is not simply a reflection of common genes influencing hyperactivity and intelligence or achievement and intelligence.
The overlapping genetic effects between hyperactivity and achievement could arise two ways. First, it could be that some of the genes that influence hyperactivity also influence academic achievement. However, the association might be less direct. The relation between hyperactivity and achievement could arise indirectly as a result of genes influencing one behavior, which in turn, influences the other. For example, it may be that behaviors associated with hyperactivity, which is genetically influenced, may make it harder for child to learn in the classroom situation.
Whatever the mechanism responsible (i.e., direct or indirect), the finding of substantial genetic overlap between hyperactivity and achievement has important implications for research searching for genes associated with the two behaviors. Given that approximately half of the genetic influences are common to both behaviors, there is a reasonable chance that some of the specific genes found for hyperactivity may also influence academic achievement. Consequently, researchers can use molecular genetic findings about one behavior to inform research about the other.
Saudino, K. J. & Plomin, R. (2007). Why Are Hyperactivity and Academic Achievement Related? Child Development, 78, 972-986.
The Twins Early Development Study (TEDS) is supported by program grant G9424799 from the UK Medical Research Council. Dr. Saudino is supported in part by grant MH062375 from the National Institute of Mental Health.