Prenatal tobacco exposure and psychiatric outcomes in adolescence: is the effect mediated through birth weight?

OBJECTIVE This study aims to examine the associations between prenatal exposure to maternal smoking, birthweight and persistent offspring psychiatric symptoms. Additionally we aim to examine whether the relationship between prenatal maternal smoking and persistent offspring psychiatric symptoms is mediated by offspring birthweight. METHODS This study used the Growing Up in Ireland (GUI) longitudinal cohort. The GUI is a nationally representative longitudinal study of children which consisted of three data collection waves, at ages 9, 13 and 17 years. Logistic regression analysis was used to examine associations between prenatal tobacco exposure, and offspring psychiatric symptoms. Linear regression was used to examine associations between prenatal tobacco exposure and offspring birthweight. We conducted a mediation analysis examining potential aetiological pathways linking maternal smoking during pregnancy, offspring birthweight and later offspring psychiatric symptoms. All analyses were adjusted for confounders including household income, maternal level of education and family psychiatric history. Additionally, examination of birthweight and subsequent psychiatric symptoms also controlled for prematurity. RESULTS We found that the association between prenatal tobacco exposure and later psychiatric symptoms is mediated by birthweight. CONCLUSIONS This works provides further evidence that maternal smoking during pregnancy is an important modifiable lifestyle factor that has an impact not just on the physical health of offspring but also their mental well-being. Supporting women with structured smoking cessation programmes at the earliest stages of pregnancy should be a public health priority.