Why autism rates in the US are high, experts explain what's driving the crisis

The United States now reports that one in 31 children has autism, a figure widely described as among the highest in the developed world. The rate marks a steep rise from about one in 150 children in 2000. By comparison, several European countries report lower prevalence: France and Germany around one in 100, Sweden about seven in 1,000, and the United Kingdom and Canada closer to one in 50.

Experts say the U.S. gap largely reflects how autism is defined and diagnosed, as well as how openly families and clinicians discuss it. A cross-border view cited by researchers points to different diagnostic benchmarks, with the United States using broader criteria than many European systems and a more aggressive screening environment that flags milder cases earlier. In the United States, the DSM-5 system permits a diagnosis if a single criterion is present in some contexts, whereas many European countries rely on the ICD-11 framework, which can be more restrictive in what qualifies as autism. Dr. Jeff Singer, a senior fellow at the Cato Institute’s Health Policy Studies, said the divergence in medical practice and health systems helps explain the discrepancy, adding that the differences extend beyond DSM-5 versus ICD-11.

In the United States, the American Academy of Pediatrics recommends universal autism screening at 18 and 24 months. In many European countries, however, monitoring is not universal and there are fewer systematic opportunities to catch children who may be on the spectrum. Britain, Germany and France do not have universal screening guidelines, and doctors typically screen for autism only if parents raise concerns. This difference in screening cadence is cited by some experts as contributing to higher reported prevalence in the U.S. but also means cases in Europe may go undiagnosed or reported less consistently.

Beyond diagnostic frameworks and screening, other risk factors are debated as potential contributors to the U.S. rate. Obesity is markedly more common among American adults than in many European populations: roughly 40 percent of U.S. adults are obese, compared with about 26 percent in the United Kingdom, 20 percent in Germany, and 17 percent in France. A 2024 study estimated that 18.7 percent of pregnant people in North America were obese, versus 12.1 percent in Europe. Obesity during pregnancy is associated with a higher risk of stillbirths and birth defects, and some researchers have linked maternal obesity to an increased risk of autism in offspring. A 2024 Australian study, for example, found that children of mothers who were obese during pregnancy had about twice the risk of autism compared with those whose mothers were not obese. Dr. Randa Jaafar, a pain specialist in New York City, explained that obesity can influence brain development in the fetus through altered blood sugar regulation and metabolic stress.

Another factor discussed by researchers is maternal age. Trends show that pregnancies in the United States increasingly occur among older mothers, with more women having children after age 30. In 2023, about one in five pregnancies involved a mother over 35, and roughly four percent of births occurred to women aged 40 and over. By comparison, estimates for Europe show a similar shift toward older ages, but experts caution that the link to autism is not fully understood. Some studies have tied later pregnancies to higher autism risk, potentially reflecting longer exposure to environmental factors or toxins or cumulative biological changes in eggs with age. Dr. Singer noted that the mid-30s has long been associated with higher risk of chromosomal abnormalities and autism, particularly for women over 35, and he emphasized that age-related risk must be considered alongside broader systemic and environmental factors.

Experts caution that claims connecting Tylenol (acetaminophen) use during pregnancy to autism risk require careful interpretation. Former President Donald Trump and other officials highlighted questions about acetaminophen at a recent press conference, but researchers warned that the evidence is mixed and that the topic is not settled science. Dr. Singer summarized the nuanced view: "There are many substances that can cause issues during pregnancy; no one is denying that. American experts surveyed the literature and they pointed out that everything was a trade-off; a high fever during pregnancy is also risky. I would say that it is unhelpful to have the federal government weight in on this. We are on this, we are investigating, my message to politicians is please for them to not get involved." He added that routine screening and broader diagnostic criteria in the United States contribute to higher reported rates, even as researchers search for clearer causal links.

Putting the pieces together, the rise in autism diagnoses in the United States appears to be driven by a combination of diagnostic definitional breadth, more systematic screening, and demographic and health trends that may influence neurodevelopment. The cross-continental pattern is less about a single cause and more about how different health systems, surveillance capabilities, and population risk profiles shape what societies classify as autism and how many children are identified as having the condition. While some factors—such as obesity and age at childbirth—have plausible links to developmental outcomes, experts stress that firm conclusions about causal pathways remain elusive and that ongoing research and careful interpretation of international data are essential.

The topic remains a focal point for public health officials, clinicians, and families alike as they work toward early identification, access to services, and support for children on the spectrum and their caregivers. The United States continues to rely on a robust, if debated, framework for detecting autism early, while other countries grapple with balancing screening practices, resource availability, and the need for consistent data to inform policy and care. In the meantime, patients and families navigate a complex landscape of guidance, diagnoses, and services that reflect both scientific uncertainty and the urgent demand for early intervention.