The Causes of Autism

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2021- Association of Phthalate exposure with autistic traits in children

Environmental International, 157 (2021), 106775

Who are the gorgeous authors?

Johanna Inhyang Kim, Jung Lee, Kyung-Shin Lee, Young Ah Lee, Choong Ho Shin, Yun-Chul Hong, Bung-Nyun Kim, Youn-Hee Lim

What was the study about?

Discover the link between endocrine-disrupting chemicals, specifically phthalates, and autistic traits in children with this insightful study. Conducted as part of the Environment and Development of Children (EDC) study, a long-term birth cohort in South Korea, researchers aimed to determine the sensitive time frames for phthalate exposure that lead to negative effects on autistic traits in children, taking into account their sex. Findings from this study also highlight the overall association between phthalate exposure and autistic traits over time.

What previous research exists on this topic?

Several studies have explored the relationship between phthalate exposure and autistic traits. However, their findings have been inconsistent, with some reporting slight or indeterminate changes in social behaviors, while others have shown a positive association between phthalate exposure and autistic traits.

Previous studies have also been limited in identifying susceptible time periods for exposure. For example, prenatal phthalate studies did not account for postnatal phthalate levels and vice versa, leading to a gap in understanding the impact of exposure during different time windows. This study aims to fill that gap by investigating various time points of phthalate exposure in children and their association with autistic traits.

What methods were used?

The relationship between phthalate exposure and autistic traits was investigated by measuring phthalate metabolite levels in urine samples taken from mothers during pregnancy and their children at ages 4, 6, and 8 years. Autistic traits were assessed using the Social Communication Questionnaire (SCQ) at ages 4, 6, and 8 years.

To ensure robust analysis, several statistical methods were employed, including Pearson correlation coefficients, univariate Poisson regression models, linear regression models, intraclass correlation coefficients, and generalized estimating equation (GEE) models. The researchers also controlled for potential covariates based on previous literature, with different sets of covariates controlled for models related to different exposure time windows (prenatal and postnatal). This study was conducted as part of an ongoing prospective birth cohort in South Korea called the Environment and Development of Children (EDC) study.

What were the findings?

In this study, researchers found positive associations between prenatal and childhood exposure to certain types of phthalate metabolites, such as MEHHP and MEOHP, and autistic traits in young and school-aged children. The association was stronger in boys compared to girls.

Additionally, the phthalate metabolite MnBP showed a significant association with SCQ scores at age 8, but not as distinctly between the sexes.

These findings suggest that the timing of exposure and the sex of the subject play a role in identifying susceptible periods of phthalate exposure related to autistic traits.

What differences were found between boys and girls?

The study discovered that boys were more strongly associated with prenatal exposure to MEHHP and MEOHP and SCQ scores than girls. The study found that MEHHP exposure during pregnancy was significantly associated with SCQ scores at ages 4 and 6 in boys, but not in girls.

Likewise, exposure to MEHHP at age 4 was significantly associated with SCQ scores at age 8 in boys, but not in girls. A similar sex-specific association was observed for MEOHP. MnBP, on the other hand, showed mixed findings.

These findings suggest that boys may be more vulnerable to phthalate exposure related to autistic traits during prenatal and childhood periods. However, more research is needed to understand the underlying mechanisms and implications of the observed sex difference.

What were the limitations of the study?

While the study sheds light on the relationship between phthalate exposure and autistic traits, there are several limitations to consider. Firstly, the assessment of autistic traits was based on a questionnaire rather than a more refined diagnostic measure.

Secondly, the study only examined three types of phthalate metabolites, leaving the effects of other types of phthalates unexplored.

Thirdly, the study sample was limited to children from high socio-economic status (SES) families and those with high maternal IQ, which may limit the generalizability of the findings to other populations.

Moreover, the authors note that they were unable to control for some potentially important confounding factors, such as postnatal stress exposure and maternal dietary intake during pregnancy.

Finally, it’s important to note that causal inference cannot be established due to the observational nature of the study.

What should future research look into?

Future research should investigate the association between phthalate exposure and autistic traits in larger and more diverse populations. Studies should assess phthalate levels at multiple time points within each individual, using pooled measurements of phthalate levels instead of spot urine samples.

Furthermore, research should explore the effects of other types of phthalates on autistic traits. Additionally, measuring postnatal factors that may affect brain development and the dietary intake of mothers during pregnancy could provide a more comprehensive assessment of the potential effects of phthalate exposure on autistic traits.

Finally, future studies should use refined measures of autistic traits or autism spectrum disorder diagnosis to provide conclusive evidence regarding the impact of phthalate exposure on autism risk.

Can I read the full study somewhere?

Definitely. Right here.

Shh. Quiet in the hall.

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