Introduction

Academic concerns and problems are quite common in children and adolescents. While it has been estimated that approximately 20% of the general population in the USA experience difficulties with some form of academic performance [1], current prevalence rates suggest that approximately 6% of the general population meet the necessary diagnostic criteria for a specific learning disorder [2]. There is significant discussion both in the literature and among clinicians and researchers regarding how to appropriately classify and subsequently diagnose a specific learning disorder (LD). Traditionally, it was assumed that a specific learning disorder exists when there is a significant discrepancy between a child's cognitive ability and achievement in reading, mathematics, or written expression. However, within the USA, changes have occurred over the past decade regarding the criteria used for determining a specific learning disorder. These changes have taken place mainly in response to the demonstrated limitations of the ability–achievement model of LD [3]. Currently, categorization of a child's LD is based on a multi-tiered process involving, ideally, early identification and intervention, and review of response to intervention (RTI).

Three primary specific learning disorders are classified in the DSM-IV-TR: Reading Disorder, Mathematics Disorder, and Disorder of Written Expression. A fourth, Learning Disorder, Not Otherwise Specified (LD-NOS), serves as a grouping for patterns of learning difficulty that are not academic subject specific (i.e. nonverbal learning disorder is characterized as LD-NOS).