Comorbidity of mathematics and reading deficits: evidence for a genetic etiology.

In order to assess the genetic etiology of the comorbidity of reading and mathematics difficulties, data were ascertained from two samples: (1) 102 identical and 77 same-sex fraternal twin pairs in which at least one member of each pair is reading disabled and (2) 42 identical and 23 same-sex fraternal twin pairs in which at least one member is math disabled. Composite reading and mathematics performance data from each sample were fitted to the basic multiple regression model for the analysis of selected twin data and its bivariate extension. Resulting estimates of bivariate heritability and the genetic correlation between the reading and the mathematics performance measures suggest that the comorbidity between mathematics and reading difficulties is due in part to genetic influences.