smoke during their pregnancies share other risk factors with their children and it may be these other risk factors that are associated with the observed adverse outcomes rather than only maternal cigarette smoking during pregnancy per se (Kuja-Halkola, D’Onofrio, Iliadou, Langstrom, & Lichtenstein, 2010). These factors can include unmeasured familial environmental influences, such as secondhand smoke, socio-economic status, and parental education. Additional factors might be genetic influences, such as genetic variation influencing (i) neurocognitive phenotypes through non-exposure contingent mechanisms, (ii) pharmacokinetic and/or pharmacodynamic aspects of nicotinic effects, or (iii) metabolism of the 4000+ other xenobiotics (e.g., foreign substances) found in cigarette smoke. Epigenetic modification has long been considered a possible influence in this regard, but, as indicated by the present review, largely remains to be empirically tested when it comes to behavioral or neurodevelopmental phenotypes.
