Effects of chemical exposure and social environment on the developing brain

The developing brain is exceptionally sensitive to environmental influences, and two recent papers lead by scientists at the CREAL have analysed the effect of several variables – chemical exposure and social environment – in neurodevelopment of infants. In the specific cases studied, the effect didn’t seem to be very substantial.

One of the articles was published in the American Journal of Epidemiology, and it focuses on the potential effect of prenatal exposure to mercury, since it is known that vulnerability of the central nervous system to this metal is increased during early development. The scientists examined 1,683 children who are part of the INMA (Environment and Childhood) Project from 4 regions of Spain between 2003 and 2010. The mercury levels at the cord blood were analyzed by atomic absorption spectrometry, and infant neurodevelopment was assessed around age 14 months by the Bayley Scales of Infant Development – a standard series of measurements originally developed by psychologist Nancy Bayley and which are used to assess the motor, language, and cognitive development of children aged 0-3.

Although the maternal-birth cohort studied comes from moderate-high fish consumption areas, and mercury is found primarily in fish, even a doubling in total mercury levels did not show an association with mental or psychomotor developmental delay. When findings where stratified by sex, there was a slight negative association between prenatal exposure to total mercury and psychomotor development among female infants, but the researchers admit that follow-up is required to confirm these results.

The second paper, published in Gaceta Sanitaria, wanted to examine the effect of maternal intelligence and mental health, taking into account also maternal occupational social class and education, on the neuropsychological development of their children. The subjects studied were also from the INMA project and the children were, again, analysed at 14 months. The mothers’ intelligence and mental health were assessed by professional psychologists and standard tests and questionnaires.

The authors found that maternal IQ plays an important role in the first stages of cognitive development in children in the more disadvantaged occupational social classes. For the other groups, the effects of maternal IQ on cognitive development were mostly explained by maternal education. As per maternal mental health, it had no effect on the childrens’ neurodevelopment, although the authors say this might be because the study was performed in a non-clinical population in which mothers were not suffering from any other serious depressive or psychiatric disorders.

References:
Llop S, Guxens M, Murcia M, Lertxundi A, Ramon R, Riaño I, Rebagliato M, Ibarluzea J, Tardon A, Sunyer J, Ballester F, on Behalf of the INMA Project. Prenatal Exposure to Mercury and Infant Neurodevelopment in a Multicenter Cohort in Spain: Study of Potential Modifiers. Am J Epidemiol. 2012 Jan 27;

Forns J, Julvez J, García-Esteban R, Guxens M, Ferrer M, Grellier J, Vrijheid M, Sunyer J. Maternal intelligence-mental health and child neuropsychological development at age 14 months. Gac Sanit. 2012 Jan 26;

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