Scientists have long wondered why autism spectrum disorder (ASD) is diagnosed three times more often in boys than girls. A new systematic review in Frontiers in Child and Adolescent Psychiatry investigated whether phthalates might play a role. These chemicals are added to plastics to make them flexible and are found in food packaging, cosmetics, toys, and household products.
Phthalates are "endocrine-disrupting chemicals," meaning they interfere with the body's hormone systems during sensitive periods of development, particularly in the womb and early childhood.
Boys may be more vulnerable to prenatal chemical exposure
Researchers analysed 18 studies of children from infancy through adolescence. The studies measured phthalate exposure through urine and blood samples taken during pregnancy and early childhood, then tracked autistic traits using standardised tools like the Social Responsiveness Scale and Autism Diagnostic Observation Schedule.
The pattern emerging from the data is noteworthy: prenatal phthalate exposure, especially during the first and second trimesters, appears linked to subtle increases in autistic traits. Some evidence suggests boys may be more susceptible to these effects than girls. However, the researchers emphasise that while the signal is worth investigating further, the evidence across studies varies significantly.
The evidence is still limited—this is not yet proven
It's crucial to understand what this review does and doesn't show. The studies found associations between chemical exposure and autistic traits, but they cannot prove that phthalates directly cause autism. The sample sizes in individual studies were often small, and the overall body of evidence remains preliminary. This is an important finding that warrants continued research, not a confirmed cause-and-effect relationship.
Practical steps to reduce exposure during pregnancy and early childhood
- Avoid heating or storing food in plastic containers, especially during pregnancy and your child's first years; use glass, stainless steel, or ceramic instead.
- Choose products labelled "BPA-free" and "phthalate-free" for toys, food packaging, and cosmetics.
- Reduce reliance on heavily packaged and processed foods; opt for fresh produce and loose items when possible.