Developmental dyscalculia is a familial learning disability

Whereas current evidence attests to a genetic component in the etiology of dyslexia and attention-deficit/hyperactivity disorder (ADHD), Little is kno wn about the role of genetics in developmental dyscalculia (DC). The object ive of this study was to determine the familial aggregation of DC. Siblings and parents of children with DC were assessed for arithmetic, reading and attention disorders. The criteria for DC were an IQ higher than 85, poor pe rformance in arithmetic, and a significant discrepancy between arithmetic a chievement and IQ. The study group was composed of 39 children with DC, 21 mothers, 22 fathers, 90 siblings, and 16 second-degree relatives. We found that 66% of mothers, 40% of fathers, 53% of siblings, and 44% of second-deg ree relatives had DC. The intraclass correlation between the sib pairs was .27. A 95% confidential interval (CI) for the prevalence of DC among siblin gs of DC probands (see Note 1) ranged from 40% to 64%, indicating a familia l prevalence almost tenfold higher than expected for the general population . IQ and attention problems were not risk factors for DC. We conclude that DC, like other learning disabilities, has a significant familial aggregatio n, suggesting a role for genetics in the evolution of this disorder.