{'fraction_non_alphanumeric': 0.020250466293631763, 'fraction_numerical': 0.003996802557953637, 'mean_word_length': 5.825454545454545, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Commentary on Lotfipour et al. (2014): Taking a balanced view on prenatal smoking on adolescent health outcomes.

Prenatal maternal smoking is an established risk for offspring behavioral problems and psychiatric symptoms [1–4]. Less understood is the mechanism of this unpropitious effect. Biological explanations, such as carbon monoxide, nicotine and toxin exposure in utero, resulting in dysregulation of neurodevelopment, are frequently cited as explanatory factors [1–4]. Given that the negative effects of prenatal maternal smoking extend well into adolescence, other proximal, casual pathways are also plausible. However, there is a paucity of research examining these factors. Loutfipour et al.’s examination of the salient environmental mediation pathways between prenatal maternal smoking and adolescent offspring drug use behaviors [5] makes an important contribution to closing the research gap. Specifically, they found that in geographically discrete, large adolescent samples, prenatal maternal cigarette smoking exerted an influence on adolescent drug use through its effect on externalizing behaviors and peer drug use. This finding underscores the importance of examining proximal environmental factors besides prenatal maternal smoking that may be critical in explaining future risk behaviors. Such balanced views are critical in expanding the scientific discourse on the etiology of the long-lasting effects on the health of the offspring that have been attributed to prenatal maternal smoking. Other researchers have questioned the magnitude of the association between prenatal maternal smoking and adverse offspring outcomes and have called for carefully designed, methodologically rigorous studies to be conducted, which can provide more refined estimates of these associations (see review by Knopik [6]). Several studies showed that, after accounting for the genetic and environmental influences, the effect of prenatal maternal smoking on offspring externalizing behaviors significantly decreases and, in some cases, fails to reach statistical significance [7–11]. These findings suggest that gene × environment interactions may mediate this association [12]. Mothers who smoke while pregnant may be genetically predisposed to engage in risk behaviors, and this genetic risk may be transmitted to their offspring either directly or indirectly via exposing offspring to environmental influences that may jointly increase the risk for adolescent risk behaviors (e.g. exposure to secondhand smoking, permissive parenting). If this is the case, then the association between prenatal maternal smoking and offspring outcomes could be driven, at least in part, by genetic factors rather than being attributable solely to exposure to cigarette smoke in utero. Taken together, the existing evidence suggests that the influence of prenatal maternal smoking and subsequent behavioral problems is highly complex. The inability to separate prenatal exposure effects from other confounding genetic and environmental factors among humans makes clarifying these associations a particular challenge. Thus, research should continue to explore myriad possible pathways before drawing any decisive conclusions. Disentangling the etiology of the negative child and adolescent outcomes that have been attributed to prenatal maternal smoking continues to be an important priority because of its ability to inform interventions. Not only is it important for pregnant women to stop smoking, but interventions may also focus on maternal psychopathology, improving parenting skills and decreasing exposure to second-hand smoking. These and other risks that smoking pregnant women face may constitute equally important areas for intervention and research.