Commentary: 'Unhealthy diet,' nutrient status, and ADHD symptoms: a confounding role for environmental nitrous oxide exposure - reflections on Rijlaarsdam et al. (2016).

Rijlaarsdam et al. (2016) recently published their findings utilizing a longitudinal design showing that prenatal 'unhealthy diet' was positively associated with IGF2 DNA methylation at birth across both youth cohorts. However, only in the EOP youth was prenatal 'unhealthy diet' positively associated with ADHD symptoms presumably through IGF2 DNA hypermethylation. Rijlaarsdam et al.'s () choice to assess high fat and sugar diet with the Food Frequency Questionnaire (FFQ) may offer some indication as to prenatal nutrient status, as the foods identified by the FFQ in their study are relatively low in free choline. It has been shown that gestational choline deficiency in rats leads to hypermethylation of IGF2. Consistent with the literature describing an association between air pollution and cognitive neurodevelopmental impairment, the author of this commentary has previously proposed through empirical investigation that chronic environmental exposure to the trace levels of the pervasive air pollutant, nitrous oxide (N