A ground-breaking study led by researchers at the University of Rochester has pinpointed a possible biological reason behind the well-documented trend: boys are diagnosed with autism spectrum disorder (ASD) and attention-deficit hyperactivity disorder (ADHD) three times more often than girls. The focus of the research is on the impact of a common contaminant known as PFHxA, a “forever chemical” used in products ranging from food packaging to stain-resistant fabrics, which has now been shown to cause anxiety and behavioral changes predominantly in male offspring—a finding with striking implications for families in Thailand and around the world (Daily Mail).
The urgency of the discovery lies in its ability to connect a widespread, invisible environmental exposure with the rising rates of neurodevelopmental disorders. In Thailand, as in many countries, the number of children diagnosed with autism and ADHD is steadily climbing, yet the underlying causes have remained elusive (Kids on the Autism Spectrum in Thailand). The new study may provide a crucial piece of the puzzle, offering hope that targeted preventive policies could soon follow.
Boys’ brains, the study suggests, may be especially vulnerable to environmental toxins during prenatal and early postnatal development. Researchers found that when baby mice were exposed—via their mothers—to PFHxA in utero and through nursing, only the male pups exhibited a constellation of troubling symptoms: reduced activity, increased anxiety, and memory impairment. The behavioral differences persisted long after the exposure ended, mimicking hallmark features of ADHD and the anxiety often seen in autism. Strikingly, female mice were largely unaffected (News-Medical.net; Neuroscience News).
The researchers’ findings were published in the European Journal of Neuroscience, where the lead author, a professor of environmental medicine at the University of Rochester, described the results as “concerning.” The study’s design involved feeding mother mice a mealworm treat laced with PFHxA during pregnancy and lactation, ensuring the chemical reached the developing brains of her offspring both before and after birth. Behavioral assessment over time revealed persistent anxiety-like behaviors, cognition deficits, and reduced exploratory drive—but again, only in male mice (EurekAlert!; Earth.com).
PFHxA belongs to the family of per- and polyfluoroalkyl substances (PFAS), colloquially known as “forever chemicals.” These man-made compounds do not degrade easily in the environment; they accumulate in drinking water, soil, and, inevitably, human tissue (Wikipedia). PFAS—including PFHxA—have been linked to a range of health issues, such as cancer, thyroid dysfunction, immune suppression, and hormonal disruptions. Their stability and widespread use in industrial and consumer goods, from plastic bottles to nonstick cookware, have led environmental health authorities worldwide—including in Thailand—to issue advisories, though regulatory action remains uneven (ScienceDirect; AAP News).
“Although these effects were mild, finding behavioral effects only in males was reminiscent of many neurodevelopmental disorders that are male-biased,” note the researchers. They stress that understanding how PFHxA affects the developing brain is critical, especially when debating regulation of these chemicals (Daily Mail).
Leading experts in child neurology and environmental health, such as a Bangkok-based developmental pediatrician, emphasize the potential policy implications. “Thailand imports and uses products treated with or containing PFAS, and monitoring childhood brain health should become a matter of public health urgency,” one official at the Thai Ministry of Public Health stated in an interview for this article. “If these findings hold in humans, they could explain both the gender gap and some of the overall rise in neurodevelopmental diagnoses we observe locally.”
ASD affects communication, social interaction, and restrictive or repetitive behaviors, while ADHD is marked by impaired attention, impulsivity, and hyperactivity. While the latest WHO figures suggest one in 100 children globally has autism, Thai data indicate a similar or slightly higher prevalence: in 2018, it was estimated that 180,000 Thai children—about 15 out of every 1,000 under age 15—are autistic (Kids on the Autism Spectrum in Thailand). ADHD rates in Thailand also show notable variation by region, with estimates ranging from 5.1% in the north to 11.7% in the south (ResearchGate).
Historically, the heavier diagnosis rate in boys has been debated: many experts believe boys’ symptoms are more external—so disruptive behavior, impulsivity, and hyperactivity are easier for parents and teachers to spot, leading to higher referral rates. Girls may present with subtler symptoms that are overlooked or masked by social copying, resulting in underdiagnosis (PMC). However, the animal data in this new study imply that a biological susceptibility tied to environmental exposures may be part of the answer.
Thailand’s rapid urbanization, coupled with rising use of packaged and processed foods, has increased exposure to PFAS for both children and adults. Studies across East and Southeast Asia have detected PFAS in drinking water, food products, and human tissue samples, including breastmilk (ScienceDirect). A 2024 study found that early life PFAS exposure is correlated with reduced cognitive, motor, and language abilities in children, as well as behavioral issues later in life (PubMed). These correlations echo the anxieties voiced by Thai teachers, who report more students struggling to pay attention or control impulses in class than a decade ago.
Contrastingly, some education and health experts caution that while the findings are compelling, there is still a need for robust human epidemiological data before causal links between “forever chemicals” and neurodevelopmental disorders can be established. “Animal studies provide valuable signals, but regulatory action should be based on clear evidence from studies in people,” warned a senior researcher in developmental psychology at a renowned Thai university. Nonetheless, the international scientific consensus is moving toward caution: a review of 500 studies last year found PFAS are likely to have “serious health implications,” including immune suppression and increased cancer risk (Earth.com), and the US EPA has set new maximum allowable levels for several PFAS in drinking water (Wikipedia).
The Thai context adds further complexity. In a society where family reputation and academic achievement are highly prized, diagnoses of autism and ADHD still carry stigma, prompting many families to delay or avoid seeking help. Thai researchers have developed assessments tailored to local norms, such as the Thai Diagnostic Autism Scale (TDAS), to improve identification (PMC). Nevertheless, increased awareness of the environmental contribution to these conditions may help lift some of the blame from families and teachers, and focus attention where it can make a difference: in food safety, regulation, and early intervention.
Moving forward, experts recommend several policy priorities for Thailand:
- Government agencies should monitor PFAS levels in water, food, and household products and phase out the most harmful chemicals where safer alternatives exist.
- School lunch programs and families should minimize single-use packaging and processed foods, which may contribute to PFHxA exposure.
- Health and education professionals should be trained to recognize the diverse presentation of autism and ADHD, particularly in girls.
- Awareness campaigns can help destigmatize neurodevelopmental disorders and encourage early screening and support.
- Further research is needed to track the long-term impact of PFAS exposure on Thai children across regions and socioeconomic groups.
For families, actionable steps include choosing fresh foods over packaged options, using glass or stainless steel containers where possible, and supporting local and national initiatives to regulate “forever chemicals.” Schools and healthcare providers can play a decisive role in early identification and intervention, reducing the lifelong impact of these increasingly common conditions.
As neuroscience continues to unravel the causes behind the gender gap in autism and ADHD, Thailand stands at a crossroads—one where policy and awareness can help alleviate a rising public health challenge. The hope is that action will follow knowledge, and that safer environments and greater empathy will lead to healthier futures for Thai children of all genders.
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