) suggested ASD could be considered an extreme expression of normal male, compared to female, phenotypic profiles.
The ASD sample in the present study does not reflect the true national prevalence rate of ASD, as the present study due to the fact that not all children in Norway participated, and that all children with missing responses on the M-CHAT were excluded.
At the same time, new cases of ASD will be diagnosed with increasing age and subsequently listed in NPR (Súren et al. Children in the current sample were born between 20 and at the linkage to NPR, autumn 2014, the youngest children in the sample were still only 5 years of age.
The most frequently reported sex difference in ASD is the disproportionally higher male to female prevalence, consistently reported since the seminal studies by Kanner () reported across studies male to female prevalence ratios ranging from 4.3:1, with 5.5:1 in groups within the normal IQ range.
For moderate to severe intellectual disability male to female ratios of 1.33:1 (Mc Carthy et al. While numerous theories have been forwarded to explain the causal mechanisms of this predominantly high male–female ratio in ASD, the topic remains widely debated in the current literature.
For example, the positive correlation between intellectual disability and severity of symptoms (Carter et al.
), combined with the fact that males are more prone to developmental delay have led some to hypothesize that the higher prevalence of autism in males stems from a greater risk of developmental disability (Boyle et al. The exact nature of this relationship is unclear, and studies have found evidence that sex differences in cognitive performance, adaptive abilities and repetitive behaviors do not appear to be ASD specific, but instead bear a closer resemblance to those found in typically developing children (Messinger et al. However, other viewpoints stress specific biological factors related to autism, e.g.However, controlling for total M-CHAT failures, this male disadvantage was more equivocal and many classically ASD-associated features were found more common in non-ASD.Within ASD, females showed relative strengths in joint attention, but impairments in imitation.This perspective is consistent with the Research Domain Criteria (RDo C: Insel et al. The overall aim for the present study is to examine sex differences in ASD-relevant behaviors as endorsed by parents in a cohort of children between 17 and 30 months of age. Mo Ba is a prospective population-based pregnancy cohort study established by the Norwegian Institute of Public Health.Participants included pregnant mothers recruited during the years 1999–2010 at ultrasound examinations at approximately week 18 of pregnancy.In addition, a list of 6 out of the 23 M-CHAT items constituting the most critical items in predicting an ASD diagnosis (Robins et al.