Taxometrics and developmental psychopathology.

Developmental psychopathologists have criticized categorical classification systems for their inability to account for within-group heterogeneity in biological, etiological. developmental, and cultural influences on behavior. Dichotomizing continuous scores of symptom severity is also inadvisable statistically. Perhaps because of a resulting wariness of categorizing, few explorations into the ontological status of traits or disorders as dimensional versus discrete have been conducted. It is argued here that the limitations of categorizing have little to do with the ontological status of traits and that developmental psychopathologists should be concerned with identifying discrete behavioral syndromes. Common taxometric methods for resolving discrete traits are described, and questions of concern to developmental psychopathologists are outlined that can be addressed through taxometrics studies. These include (a) identifying children who are at risk for future psychopathology, (b) identifying discrete subtypes within current diagnostic classes, (c) locating sensitive periods in the development of discrete pathological traits, (d) discovering moderators of treatment outcome, and (e) elucidating mechanisms of equifinality and multifinality. Although most behavioral traits probably are distributed continuously, identifying those that are discrete will advance the science of developmental psychopathology. Disorders for which taxometric analyses might be applied include anxiety, attention deficit hyperactivity disorder, autism spectrum disorders, conduct problems, depression, and schizophrenia.