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In the extreme male brain theory of autism sex steroid hormones are hypothesized to influence brain development and to mediate sex differences in developmental psychopathology. Within this scope we examined the sex ratio (proportion of males) in siblings of individuals diagnosed with autism spectrum disorders (ASD). We did a nationwide, register based cohort study of the sex ratio in 17,380 siblings of the 10,297 patients diagnosed with ASD at age 17 years and younger and registered in the nationwide Danish Psychiatric Central Register between 1994 and 2012. Among the 17,380 siblings 8,828 were males and 8,552 females. This yields a sex ratio of 0.508, which is not different from the Danish live birth sex ratio of 0.513 during the relevant years (P = 0.18). Overall, our findings provide no support for the hypothesis that there are relatively more males among the siblings of people with ASD. Accordingly, our results do not give support to the extreme male brain theory of autism.

A 20 item observational measure of social functioning, the Impression of Interviewee rating scale, is one of three measures devised to assess the broader autism phenotype. The sample studied included families containing at least two individuals with autism spectrum disorder; observations were undertaken by the researcher who interviewed the subject. An exploratory factor analysis suggested a single factor was most appropriate (Cronbach's α of 0.78). There was a modest but significant retest correlation of 0.42. Correlations between live ratings and blind consensus ratings of vignettes were high (0.93). Correlations with the interview measures were moderate but statistically significant. In conclusion, the observational scale provides a promising start but further work is required before general use can be recommended.

The purpose of this study is to compare the prevalence and types of diseases (International classification of mental and behavioural disorders, 10th edition codes K20-K93) relating to the gastrointestinal tract in a clinical sample of 89 individuals diagnosed as children with atypical autism/pervasive developmental disorder not otherwise specified with 258 controls from the general population. All participants were screened through the nationwide Danish National Hospital Register. The average observation time was 32.9 years, and mean age at the end of the observation period was 48.5 years. Among the 89 cases with atypical autism, a total of 22 (24.7%) were registered with at least one diagnosis of any disease of the gastrointestinal tract, against 47 of 258 (18.2%) in the comparison group (p = 0.22; odds ratio = 1.5; 95% confidence interval = 0.8-2.6). Without reaching statistical significance, the rate of diseases of the gastrointestinal tract was particularly high (odds ratio = 1.2) in those with intelligence quotient < 70. Overall, people with atypical autism had about the same frequency of gastric, intestinal and hepatic diseases as had controls.

There is an increased but variable risk of epilepsy in autism spectrum disorders. The objective of this study is to compare the prevalence and types of epilepsy and other central nervous system (CNS) diseases in a clinical sample of 89 individuals diagnosed as children with atypical autism (AA) with 258 matched controls from the general population. Diagnoses were based on data from the nationwide Danish National Hospital Register. The average observation time was 32.9 years, and mean age at follow-up was 48.5 years. Of the 89 individuals with AA, 20 (22.5%) were registered with at least one epilepsy diagnosis against 11 (4.3%) in the comparison group (P < 0.0001; OR 6.5; 95% CI 3.0-14.2). Other CNS diseases occurred with low frequency in both groups, and no single CNS disease (except epilepsy) was significantly more frequent among patients with AA. Low intelligence was a risk factor for epilepsy in AA.

Background: The aim of the present study was to evaluate body mass index (BMI) of children with a pervasive developmental disorder (PDD) attending two university clinics during the 1960-84 period., Methods: BMI derived from medical records of 83 consecutively admitted children with atypical autism and 115 children with Asperger syndrome were compared with the corresponding BMI percentiles in an age- and sex-matched reference population., Results: The BMI distribution of the boys, but not the girls, in both diagnostic categories was significantly lower than those of the age-matched reference populations. Approximately 15% of the boys had a BMI below the fifth percentile., Conclusions: The present findings are comparable to the results of other studies. Particular attention is given to low BMI as a potential endophenotype in boys with PDD.

The prevalence and pattern of criminal behaviour in a population of 313 former child psychiatric in-patients with pervasive developmental disorders were studied. The patients were divided into three subgroups and compared with 933 matched controls from the general population. Age at follow-up was between 25 years and 59 years. An account of convictions in the nationwide Danish Register of Criminality was used as a measure of criminal behaviour. Among 113 cases with childhood autism, .9% had been convicted. In atypical autism (n=86) and Asperger's syndrome (n=114) the percentages were 8.1% and 18.4%, respectively. The corresponding rate of convictions in the comparison groups was 18.9%, 14.7%, and 19.6% respectively. Particular attention is given to arson in Asperger's syndrome (p= .0009).