Maternal smoking during pregnancy and offspring's tobacco dependence. A study of exposure-discordant sibling pairs

- Smoking during pregnancy is not likely to cause tobacco dependence in offspring.
- Neither is pregnancy smoking associated with quit attempts in offspring.
- Genetic and early influences are likely more important for developing dependence.

BackgroundPrenatal exposure to maternal smoking has previously been linked to tobacco dependence, but confounding from genetic and early-environmental factors is of concern. The aim of this study was to clarify if maternal smoking during pregnancy may affect the onset and manifestations of tobacco dependence after taking such factors into account.MethodsThe study is based on a matched cohort of 1538 siblings discordant for prenatal exposure to maternal smoking, who participated in a survey conducted in 2010 in Sweden. Analyses were based on pairs where both siblings had been daily smokers (193 pairs) or snus users (173 pairs) at some time in their life. Participants were 19-27 years old at the time of participation. Outcomes were tobacco dependence measured with the Cigarette Dependence Scale (CDS-12) in smokers and with the adapted Smokeless Tobacco Dependence Scale (STDS-12) in snus users, and previous quit attempts. Exposure to maternal smoking during pregnancy was retrieved from the Swedish Medical Birth Register.ResultsThere was no difference in dependence scores in exposure-discordant siblings (mean difference 0.36 on CDS-12 [95% confidence interval: −1.23 to 1.95] and 0.61 on STDS-12 [95% confidence interval: −1.20 to 2.43]). Neither did the siblings differ with regard to previous quit attempts.ConclusionsMaternal smoking during pregnancy does not appear to influence tobacco dependence in adult offspring. A potential effect of heavy maternal smoking during pregnancy cannot be excluded, but genetic and environmental influences seem to be more influential for the onset of tobacco dependence.