HealthDay News — Prenatal exposure to methly mercury in fish is not associated with autism spectrum disorder (ASD) phenotypic behaviors, results of a large cohort study of mothers and children in the Indian Ocean nation Seychelles, where residents consume 10 times the amount of ocean fish as U.S. residents, indicate.
“This study shows no consistent association in children with mothers with mercury levels that were six to 10 times higher than those found in the U.S. and Europe,” study investigator Philip Davidson, PhD, an emeritus professor at University of Rochester Medical Center said in a press release. “This is a sentinel population and if it does not exist here than it probably does not exist.”
Public concern about exposure to mercury remains despite a growing body of evidence that exposure to the chemical is not associated with autism onset. Although vaccines have been suggested as a source of mercury exposure, the main source of exposure to organic mercury in humans is through methyl mercury found in fish.
To examine whether consuming too much fish during pregnancy is associated with autism, Davidson and colleagues administered the Social Communication Questionnaire to parents of a cohort of 1,784 children, adolescents and young adults. The 40-item questionnaire is widely used to screen people for ASD symptoms. Although not a diagnostic test, a score of 15 or higher warrants further evaluation.
Maternal hair samples collected around the time of birth were used to assess prenatal exposure to methyl mercury. A subset of 532 children (mean age 10 years) were also administered the Social Responsiveness Scale, a 65-item scale designed to recognize ASD symptoms in social settings. A score of 70 or greater in males and 65 or greater in females indicates a possible ASD.
The primary endpoint was Social Communication Questionnaire scores in relation to mothers’ prenatal mercury levels.
Study participants had an average prenatal methyl mercury level of 8.4 parts per million, and average score on the Social Communication Questionnaire was 8.0. Approximately 8% of participants scored 15 or higher on the Social Communication Questionnaire.
Average prenatal methyl mercury exposure for the 532 participants who were administered the Social Responsiveness Scale was 6.7 parts per million. The mean score on that test was 57.6, with 34% of participants scoring above the cut-off for possible autism.
Using linear and nonlinear regression analyses, the researchers found no consistent correlation between prenatal exposure to methyl mercury and scores on ASD screening instruments.
“In conclusion, we found no association between prenatal methyl mercury exposure and phenotypic ASD behaviors,” the researchers wrote. “Our findings contribute to the growing literature suggesting that exposure to organic forms of mercury does not play an important role in the development of ASD phenotypic behavior.”