A total population study of children, aged 13 years and under, suggested that there has been an apparent rise in the frequency of autistic disorder and autistic-like conditions (excluding Asperger's syndrome) in one area of western Sweden over the last ten years. The frequency was 4.0/100,000 in 1980, 7.5/10,000 in 1984 and 11.6/10,000 in 1988 in the city of Göteborg. Even though the prevalence rates refer to slightly different age cohorts, it was concluded that the apparent increase is in part due to better detection, but also to new cases born to immigrant parents. Typical cases of autistic disorder accounted for 75% of cases, and 20% had normal or near-normal IQs.

Twenty-eight children referred with a preliminary diagnosis of autistic disorder under age 3 yrs were extensively examined from the neuropsychiatric point of view and followed up for several months to several years. A diagnosis of autistic disorder was confirmed in 75% of the cases. A variety of associated medical conditions was identified. It was concluded that autism can be diagnosed in a substantial proportion of cases before age 3 yrs and that the neurobiological background is similar to that seen in older autistic children.

Three boys diagnosed as suffering from autistic disorder were born in Sweden to mothers born in Uganda. Two were related but the third boy was unrelated to the others. The prevalence for autistic disorder in Göteborg children born to mothers who were born in Uganda was 15% which is almost 200 times higher than in the general population of children. The possible reason for the high autism rate in this particular ethnic subgroup is discussed.

While the prognosis for autistic children is generally poor, some show substantial improvement during childhood. In a Swedish sample of five cases deterioration or severe symptom aggravation at the onset of puberty is described that followed earlier improvement. Autistic children with pubertal deterioration may constitute a meaningful subgroup of the syndrome. The matter deserves more attention in future follow-up studies.

Twenty infantile autistic children, constituting what is likely to be the majority of the total population of autistic children born in the years 1962 through 1973 and living in Göteborg, Sweden, by the end of 1978, were compared with a random population sample of 59 7-year-old Göteborg children with regard to social class. Two different social classification systems were used, one that takes account only of the father's occupation and one that includes several other parameters. The distributions of social class were almost identical in the infantile autism group and in the random group. With respect to some other social circumstances the two groups were very similar. Thus, the present results lend no support for the view that autistic children tend to come from high social classes.