The incidence, prevalence, and severity of behavior disorders among preschool-aged children in day care.

This study examined the incidence, prevalence, and severity of 14 empirically derived externalizing (unsocialized aggressive) and internalizing (socially withdrawn) behaviors among 2- through 5-year-olds attending day care. Teacher ratings were obtained for 558 children in the incidence sample and 709 children in the expanded prevalence sample. Within each age, data were cross-tabulated by sex of child and severity of behavior, and chi-square analyses were computed. Results indicated that a substantial proportion of children in the normal pre-school population exhibit relatively high severities of selected externalizing and internalizing behaviors; this proportion varied with the age of the child and the behavior rated. Preschool-aged boys were consistently rated as demonstrating greater frequencies of externalizing behaviors than preschool-girls. The diagnostic and clinical implications of these findings are discussed.