Mild mental retardation in schoolchildren in a Swedish suburban municipality: prevalence and diagnostic aspects.

The prevalence of mild mental retardation (MMR) (IQ 50-72) was investigated in a Swedish suburban municipality with special demographic characteristics. The study population consisted of the 6397 children aged 9-15 years residing in the municipality on December 31, 1994. A total of 82 children fulfilled psychometric and adaptive criteria of MMR, corresponding to a prevalence of 12.8/1000. The prevalence was higher than that reported in previous Swedish and Finnish studies using similar case-finding methods. This can probably be explained by the lower socioeconomic status in the municipality studied and by the fact that testing is now more acceptable. Nearly 90% of the MMR children had symptoms in their preschool years, mainly motor, speech/language deviations and a relative inability to perform certain tasks. These symptoms also occur in children with minimal brain dysfunction/ deficits in attention, motor control and perception which should be taken into consideration when selecting screening tests.