Gender and Age Differences in the Core Triad of Impairments in Autism Spectrum Disorders: A Systematic Review and Meta-analysis

Abstract

Autism is an extensively studied disorder in which the gender disparity in prevalence has received much attention. In contrast, only a few studies examine gender differences in symptomatology. This systematic review and meta-analysis of 22 peer reviewed original publications examines gender differences in the core triad of impairments in autism. Gender differences were transformed and concatenated using standardized mean differences, and analyses were stratified in five age categories (toddlerhood, preschool children, childhood, adolescence, young adulthood). Boys showed more repetitive and stereotyped behavior as from the age of six, but not below the age of six. Males and females did not differ in the domain of social behavior and communication. There is an underrepresentation of females with ASD an average to high intelligence. Females could present another autistic phenotype than males. As ASD is now defined according to the male phenotype this could imply that there is an ascertainment bias. More research is needed into the female phenotype of ASD with development of appropriate instruments to detect and ascertain them.

Gender ratio in a clinical population sample, age of diagnosis and duration of assessment in children and adults with autism spectrum disorder

“…The gender ratio in all children and adolescents (3.5:1) was in keeping with national estimates (see Van Wijngaarden-Cremers et al, 2014) and was highest in the under 10 age group. A further important finding in this study was that gender ratio reduces with increasing age, being smaller for adolescents (2.3:1) than for younger children (5.5:1), thus supporting the camouflage hypothesis (Dworzynski et al, 2012) that it becomes increasingly difficult for girls to mask their symptoms of ASD over time.…”

Protective Effect or Missed Diagnosis? Females with Autism Spectrum Disorder

“…This argument is [6,42]. One issue is that there is significant variation in IQ, age, language ability and other characteristics between different samples, and therefore it is difficult to draw comparisons across different studies [6].…”

“…Gender ratios in diagnosis vary depending on the country, cohort, and characteristics of those included, but average ratios are reported at around four males for every one female [3][4][5]. However, when looking at those individuals with intellectual disability, the male-to-female ratio narrows significantly to around two-toone [6]. In addition, population-based studies, which screen all participants in order to identify cases regardless of whether they have already been diagnosed by local services, suggest that the male-to-female ratio is closer to 3:1 [7,8].…”

“…'person with autism'). diagnostic criteria [6]. This explanation suggests that significant numbers of autistic females are currently being missed by clinical services and hence the true female prevalence of ASD is still unknown.…”

Special Issue on the Topic of Autism Spectrum Disorder

“…One important and inadequately studied area is gender differences in the presentation of ASD (1). Some investigators have expressed concerns that high-functioning girls with ASD may be underidentified as a result of differences in their symptom presentation (1)(2)(3), and sex differences in ASD symptom presentation have also been suggested by some studies of lower-functioning individuals (4).…”