A prevalence methodology for mental illness and developmental disorders in rural and frontier settings

A prevalence study methodology developed for use in rural and frontier settings is described. The general method was developed over a 15 year period and has been successfully adapted and used in studies of 14 different childhood onset developmental disorders. Subjects were the 168,000 school aged children from North Dakota who were first surveyed for cases of autism--pervasive developmental disorders in 1985 and 1986. The results of the prevalence study were compared with the results of a 12-year ongoing surveillance of the cohort. The 12-year ongoing surveillance identified one case missed by the original prevalence study. Thus the original prevalence study methodology identified 98% of the cases of autism-pervasive developmental disorder in the population. This methodology may also be useful for studies of other developmental disorders in rural and frontier settings.