Early life environmental factors associated with autism spectrum disorder symptoms in children at age 2 years: A birth cohort study.
Poverty, prenatal stress, alcohol, and dirty air each raise autism trait scores at age two.
01Research in Context
What this study did
Pham et al. (2022) tracked families from pregnancy to age two. They recorded income, family structure, moms’ stress, drinking, smoking, and air quality. At age two they scored each child for autism traits using a standard checklist.
The goal was to see which early-life factors foreshadow later diagnosis.
What they found
Kids from lower-income or single-parent homes scored higher on autism traits. The same was true for kids whose moms reported high stress, drank alcohol, or lived with traffic fumes or mold.
The more risk factors present, the stronger the signal for later autism.
How this fits with other research
Jeon et al. (2026) add a medical twist: babies who needed a breathing tube before age five later showed triple the autism rate. Together the papers widen the risk lens from social hardship to neonatal trauma.
Catania et al. (1982) seems to disagree. In 1970s Sweden autism appeared equally across all social classes. The gap closes when you notice they counted full diagnoses in older children, while Cindy et al. measured subtle traits in toddlers. Poverty may show up earlier in symptom counts, not in final labels.
Rijlaarsdam et al. (2017) supply a possible why: prenatal stress can alter the oxytocin gene in newborns, nudging social development off track. The environmental story now has a biological footpath.
Why it matters
You can flag high-risk toddlers long before formal testing. Ask about income strain, lone parenting, smoking, and home air quality during intake. Add a quick autism screener at 24 months for these families. Early surveillance means earlier intervention and better long-term outcomes.
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02At a glance
03Original abstract
Mounting evidence indicates the contribution of early life environmental factors in autism spectrum disorder. We aim to report the prospective associations between early life environmental factors and autism spectrum disorder symptoms in children at the age of 2 years in a population-derived birth cohort, the Barwon Infant Study. Autism spectrum disorder symptoms at the age of 2 years strongly predicted autism spectrum disorder diagnosis by the age of 4 years (area under curve = 0.93; 95% CI (0.82, 1.00)). After adjusting for child's sex and age at the time of behavioural assessment, markers of socioeconomic disadvantage, such as lower household income and lone parental status; maternal health factors, including younger maternal age, maternal pre-pregnancy body mass index, higher gestational weight gain and prenatal maternal stress; maternal lifestyle factors, such as prenatal alcohol and environmental air pollutant exposures, including particulate matter < 2.5 μm at birth, child secondhand tobacco smoke at 12 months, dampness/mould and home heating with oil, kerosene or diesel heaters at 2 years postnatal. Lower socioeconomic indexes for area, later birth order, higher maternal prenatal depression and maternal smoking frequency had a dose-response relationship with autism spectrum disorder symptoms. Future studies on environmental factors and autism spectrum disorder should consider the reasons for the socioeconomic disparity and the combined impact of multiple environmental factors through common mechanistic pathways.
Autism : the international journal of research and practice, 2022 · doi:10.1177/13623613211068223