Developmental dyscalculia: prevalence and prognosis

The prevalence of developmental dyscalculia (DC) in the school population r anges from 3-6 %, a frequency similar to that of developmental dyslexia and ADHD. These studies fulfilled the criteria for an adequate prevalence stud y, i.e., were population based, using standardized measures to evaluate ari thmetic function. Although the variation in prevalence is within a narrow r ange, the differences are probably due to which definition of dyscalculia w as used, the age the diagnosis was made and the instrument chosen to test f or DC. The relative predominance of girls with DC may reflect a greater vul nerability to environmental influences alone or in addition to a biological predisposition. DC is not only encountered as a specific learning disabili ty but also in diverse neurological disorders, examples of which include AD HD, developmental language disorder, epilepsy, treated phenylketonuria and Fragile X syndrome. Although the long-term prognosis of DC is as yet unknow n, current data indicate that DC is a stable learning disability persisting , at least for the short term, in about half of affected children. The long -term consequences of DC and its impact on education, employment and psycho logical well-being have yet to be determined.