Why are autism diagnosis figures rising? What research says

What the review shows

The paper by Zeidan and colleagues (2022) updates an earlier review. It found a median of 65 cases per 10,000 (that is, about 1 in 100 children) compared with 62 per 10,000 in the earlier review. The estimates rose over time and differed strongly within and between sociodemographic groups. ^[1] To put the figures in context: How common is autism?

Reasons for the rise

According to the review, the time trends reflect several factors, not a single causal path. It names ^[1]:

• the increased awareness of the population and the public health response worldwide,
• changed case definitions that widened the diagnostic boundaries over time,
• the more frequent diagnosis of milder forms,
• the better recognition in groups that were more often overlooked in the past (by sex, region, origin or social status),
• more capacity in health and education systems.

It fits that the studies’ measurement methods are very different: how cases are searched for, assessed and confirmed and how well health and education systems can recognise autism influences the measured prevalence. ^[1] The developing clinical definition and the delimitation from similar conditions also had an effect. ^[1]

Examples from individual countries

The paper reports time trends in several countries: in the USA, a CDC report for 2010, 2012 and 2014 showed a rise in New Jersey, while the estimates in Arizona and Missouri remained stable; the share of children with autism and intellectual disability remained stable over time. Rises were also reported for South Korea (2008 to 2015) and Taiwan (2004 to 2010). In France, prevalence was higher in children born in 2003 than in those born in 1997, in Australia higher in those born in 2003/2004 than in those born in 1999/2000. ^[1]

What the figures do not say

• Measured prevalence is not the same as actual prevalence. Those who search more and recognise better find more. Whether the actual number has changed cannot be read from these data. ^[1]
• No simple cause. For links between social characteristics (region, origin, socioeconomic status) and prevalence, the paper found no convincing evidence of direct causal relationships; these characteristics probably act via help-seeking and access to care. ^[1]
• Sex ratio: The ratios reported ranged from 0.8 to 6.1; the authors point to possible differences in recognition, for example that assessment methods are not optimal for girls. ^[1]

Limits and open questions

• No quality assessment of the individual studies: The authors name as a limitation that the methodological quality of the studies included was not assessed and the procedure was not registered in advance. ^[1]
• Little data from Germany: The paper gives no figure for Germany; more on this is in How common is autism?.
• Environment and migration: According to the paper, the evidence for a role is weak or contradictory; studies with hypotheses set in advance would be needed. ^[1]
• State: The review appeared in 2022 and evaluates studies up to then.

What else you should know

• More recent classification: A 2026 meta-analysis comes to similar statements about differences in methods: Autism prevalence worldwide.
• What genetics contributes: Genetics and autism and Causes of autism.
• How to put studies in context: How good is a study?

Sources and literature

1. Zeidan J, Fombonne E, Scorah J, Ibrahim A, Durkin MS, Saxena S, Yusuf A, Shih A, Elsabbagh M. Global prevalence of autism: A systematic review update. Autism Research 2022;15(5):778–790. https://doi.org/10.1002/aur.2696 – Systematic review