Time trends in autism diagnosis over 20 years: a UK population-based cohort study.

BACKGROUND: Autism spectrum disorder is a diagnosis that is increasingly applied; however, previous studies have conflicting findings whether rates of diagnosis rates continue to grow in the UK. This study tested whether the proportion of people receiving a new autism diagnosis has been increasing over a twenty-year period, both overall and by subgroups. METHOD: Population-based study utilizing the Clinical Practice Research Datalink (CPRD) primary care database, which contains patients registered with practices contributing data to the CPRD between 1998 and 2018 (N = 6,786,212 in 1998 to N = 9,594,598 in 2018). 65,665 patients had a diagnosis of autism recorded in 2018. Time trend of new (incident) cases of autism diagnosis was plotted for all, and stratified by gender, diagnostic subtypes, and developmental stage: infancy and preschool, 0-5 years old; childhood, 6-11 years old; adolescence, 12-19 years old; adults, over 19 years old. RESULTS: There was a 787%, exponential increase in recorded incidence of autism diagnoses between 1998 and 2018; R2 = 0.98, exponentiated coefficient = 1.07, 95% CI [1.06, 1.08], p < .001. The increase in diagnoses was greater for females than males (exponentiated interaction coefficient = 1.02, 95% CI [1.01, 1.03], p < .001) and moderated by age band, with the greatest rises in diagnostic incidence among adults (exponentiated interaction coefficient = 1.06, 95% CI [1.04, 1.07], p < .001). CONCLUSIONS: Increases could be due to growth in prevalence or, more likely, increased reporting and application of diagnosis. Rising diagnosis among adults, females and higher functioning individuals suggest augmented recognition underpins these changes.

Understanding the Contributions of Trait Autism and Anxiety to Extreme Demand Avoidance in the Adult General Population.

Autism and anxiety are thought to be related to extreme demand avoidance (EDA), which is characterised by intense avoidance of everyday demands. However, the relative importance of autism and anxiety to EDA has yet to be investigated, and little is known about EDA in adulthood. We conducted two online survey studies (Ns = 267 and 549) with adults in the general population to establish the relative importance of autistic traits and anxiety as predictors of demand avoidance, using dominance analysis. Both autistic traits and anxiety were unique and equally important predictors of demand avoidance. These findings suggest EDA is linked to autism and are consistent with the theory that demand avoidance behaviours are potentially anxiety-driven in adults.

Is disclosing an autism spectrum disorder in school associated with reduced stigmatization?

Evidence suggests disclosing an autism diagnosis is associated with reduced stigmatization for autistic adults. However, it is unknown whether this is true for autistic adolescents. We used a vignette-and-questionnaire design to study stigmatizing attitudes with adolescents (aged 11-12 and 14-16 years, total N = 250) in a UK school. We investigated the effect of disclosing that a fictional adolescent had an autism diagnosis on stigmatizing attitudes of peers by testing the effect of disclosure of diagnosis on the social and emotional distance pupils wanted to maintain from the autistic adolescent. We also tested the effect of disclosure on peers' assessment of the adolescent's responsibility for their own behaviour. We checked to see if the effects were moderated by gender and age-group. Disclosing autism did not affect the social and emotional distance peers wanted to maintain from the autistic adolescent, but was associated with significant reduction in personal responsibility attributed to the adolescent's behaviour. Boys attributed more personal responsibility to the autistic adolescent than girls, but this gender effect was reduced when autism was disclosed. These findings suggest that disclosing autism to other pupils may be of limited use in reducing stigmatization by peers in UK schools.

Selection bias on intellectual ability in autism research: a cross-sectional review and meta-analysis.

Background: Current global estimates suggest the proportion of the population with autism spectrum disorder (ASD) who have intellectual disability (ID) is approximately 50%. Our objective was to ascertain the existence of selection bias due to under-inclusion of populations with ID across all fields of autism research. A sub-goal was to evaluate inconsistencies in reporting of findings. Methods: This review covers all original research published in 2016 in autism-specific journals with an impact factor greater than 3. Across 301 included studies, 100,245 participants had ASD. A random effects meta-analysis was used to estimate the proportion of participants without ID. Selection bias was defined as where more than 75% of participants did not have ID. Results: Meta-analysis estimated 94% of all participants identified as being on the autism spectrum in the studies reviewed did not have ID (95% CI 0.91-0.97). Eight out of ten studies demonstrated selection bias against participants with ID. The reporting of participant characteristics was generally poor: information about participants' intellectual ability was absent in 38% of studies (n = 114). Where there was selection bias on ID, only 31% of studies mentioned lack of generalisability as a limitation. Conclusions: We found selection bias against ID throughout all fields of autism research. We recommend transparent reporting about ID and strategies for inclusion for this much marginalised group.