The diagnostic categories of developmental cognitive disorders referred to as attention deficit hyperactivity disorders (ADHD) and learning disorders are relatively vague due to poorly understood etiologies and the construct validity of the diagnostic measures. Consequently, it has been difficult to establish unambiguous diagnostic criteria. Contributing to this diagnostic problem are complications resulting from the co-occurrence of two or more supposedly separate neurocognitive disorders such as comorbidity. Although comorbidity is commonly seen by practitioners and researchers, there is surprisingly little data on the topic. Research and practice can be confounded by the existence of comorbidity. Interestingly, the degree and type of comorbidity in research samples is seldom addressed in the subject descriptions of research reports. This special issue illustrates the nature of comorbidity problems in the case of developmental neurocognitive disorders and especially within and between learning and attention disorders. These problems are often encountered in this area of research and practice, and further discussion is needed concerning the diagnostic criteria and comorbidity.
Volume 11, Number 3, 1995 Contents: H. Lyytinen, Introduction: Comorbidity and Developmental Neurocognitive Disorders. P. Räsänen, T. Ahonen, Arithmetic Disabilities With and Without Reading Difficulties: A Comparison of Arithmetic Errors. T. Lamminmäki, T. Ahonen, V. Närhi, H. Lyytinen, H.T. de Barra, Attention Deficit Hyperactivity Disorder Subtypes: Are There Differences in Academic Problems? G.W. Hynd, A.E. Morgan, J.E. Edmonds, K. Black, C.A. Riccio, L. Lombardino, Reading Disabilites, Comorbid Psychopathology, and the Specificity of Neurolinguistic Deficits. J.G. Light, B.F. Pennington, J.W. Gilger, J.C. DeFries, Reading Disability and Hyperactivity Disorder: Evidence for a Common Genetic Etiology. V. Närhi, T. Ahonen, Reading Disability With or Without Attention Deficit Hyperactivity Disorder: Do Attentional Problems Make a Difference? P.T. Ackerman, R.A. Dykman, Reading-Disabled Students With and Without Comorbid Arithmetic Disability.