ABSTRACT
Throughout this book, various behavioral, social, and emotional problems of children and adolescents have been discussed most frequently in terms of their place within the two broad dimensions of externalizing and internalizing psychopathology or disorders. This broad-band taxonomic division has become the standard paradigm among researchers who investigate developmental psychopathology. Not all childhood behavioral or emotional problems t neatly within this model, however. Some disorders, as evidenced by some of the narrow-band cross-informant syndromes in the Achenbach System of Empirically Based Assessment, are considered to be mixed disorders. Within these syndrome scales, some items may load into the externalizing domain, other items may load into the internalizing domain, and some items may not load specically into either of the two broad-band domains. Some severe problems, such as psychotic disorders and pervasive developmental disorders, occur with such low frequency in the general child population that it is difcult to justify even including relevant items for them in general screening instruments. Large-scale epidemiologic studies usually identify so few cases in which these lowfrequency behaviors are present that it is difcult to ascertain accurately their appropriate classication dimensions.
