Changes in diagnosis rates and behavioural traits of autism spectrum disorder over time

BACKGROUND: The increased proportion of UK children diagnosed with autism spectrum disorder (ASD) has been attributed to improved identification, rather than true increase in incidence. AIM: To explore whether the proportion of children with diagnosis of ASD and/or the proportion with associated behavioural traits had increased over a 10-year period. METHOD: A cross-cohort comparison using regression to compare prevalence of diagnosis and behavioural traits over time. Participants were children aged 7 years assessed in 1998/1999 (n=8139) and 2007/2008 (n=13 831). RESULTS: During 1998/1999, 1.09% (95% CI 0.86–1.37) of children were reported as having ASD diagnosis compared with 1.68% (95% CI 1.42–2.00) in 2007/2008: risk ratio (RR)=1.55 (95% CI 1.17–2.06), P=0.003. The proportion of children in the population with behavioural traits associated with ASD was also larger in the later cohort: RR=1.61 (95% CI 1.35–1.92), P<0.001. Increased odds of diagnosis at the later time point was partially accounted for by adjusting for the increased proportion of children with ASD-type traits. CONCLUSIONS: Increased ASD diagnosis may partially reflect increase in rates of behaviour associated with ASD and/or greater parent/teacher recognition of associated behaviours. DECLARATION OF INTEREST: None. COPYRIGHT AND USAGE: © The Royal College of Psychiatrists 2015. This is an open access article distributed under the terms of the Creative Commons Non-Commercial, No Derivatives (CC BY-NC-ND) licence.