Familial confounding of the association between maternal smoking during pregnancy and offspring substance use and problems

The intergenerational transmission of smoking in adulthood: a 25-year study of maternal and offspring maladaptive attributes

While smoking is a major cause of mortality and morbidity, and maternal smoking is a risk factor for smoking among their offspring, the mechanisms involved in the intergenerational transmission of smoking are not well understood. This study examines the pathways from maternal and adolescent child factors, and the parent-child relationship, to smoking among the adult offspring, approximately 25 years later. Data for the present analysis were based on time waves 2 (T2; 1983) and 7 (T7; 2007-2009) of an on-going study of a community sample of mothers and their children. Offspring and mother X¯ ages were 14.1 and 40.0 years, respectively, at T2, and 36.6 and 65.0 years, respectively, at T7. At T2, trained interviewers administered individual structured interviews. Psychosocial questionnaires were self-administered at T7. Structural equation modeling (SEM) was used to analyze the interrelationships among maternal and offspring attributes (T2 and T7). SEM results indicated a satisfactory model fit (RMSEA=0.052; CFI=0.91; SRMR=0.057), and confirmed hypothesized pathways. One pathway linked maternal maladaptive attributes (T2) to the mother-adolescent child attachment relationship (T2), which was associated with the offspring's maladaptive attributes over time (T2 to T7), which then predicted the adult offspring's smoking (T7). Other pathways highlighted the stability of maternal smoking, the continuity of maladaptive attributes, and less offspring educational attainment as predictors of offspring smoking at T7. Findings suggest the importance of early interventions to treat maternal smoking, maternal and offspring maladaptive attributes, and the mother-child relationship in order to reduce risk factors for the intergenerational transmission of smoking behavior. Interventions which enhance educational success should also prove effective in reducing smoking.

Revisiting the effect of maternal smoking during pregnancy on offspring birthweight: a quasi-experimental sibling analysis in Sweden

Maternal smoking during pregnancy (SDP) seems associated with reduced birthweight in the offspring. This observation, however, is based on conventional epidemiological analyses, and it might be confounded by unobserved maternal characteristics related to both smoking habits and offspring birth weight. Therefore, we apply a quasi-experimental sibling analysis to revisit previous findings. Using the Swedish Medical Birth Register, we identified 677,922 singletons born between 2002 and 2010 from native Swedish mothers. From this population, we isolated 62,941 siblings from 28,768 mothers with discrepant habits of SDP. We applied conventional and mother-specific multilevel linear regression models to investigate the association between maternal SDP and offspring birthweight. Depending on the mother was light or heavy smoker and the timing of exposition during pregnancy (i.e., first or third trimester), the effect of smoking on birthweight reduction was between 6 and 78 g less marked in the sibling analysis than in the conventional analysis. Sibling analysis showed that continuous smoking reduces birthweight by 162 grams for mothers who were light smokers (1 to 9 cigarettes per day) and 226 g on average for those who were heavy smokers throughout the pregnancy in comparison to non-smoker mothers. Quitting smoking during pregnancy partly counteracted the smoking-related birthweight reduction by 1 to 29 g, and a subsequent smoking relapse during pregnancy reduced birthweight by 77 to 83 g. The sibling analysis provides strong evidence that maternal SDP reduces offspring birthweight, though this reduction was not as great as that observed in the conventional analysis. Our findings support public health interventions aimed to prevent SDP and to persuade those who already smoke to quit and not relapse throughout the pregnancy. Besides, further analyses are needed in order to explain the mechanisms through which smoking reduces birthweight and to identify other maternal characteristics that are common causes of both birthweight reduction and maternal smoking.

Don't throw the bathwater in with the baby

The Presidential Address of the European Association of Developmental Psychology this year concerned how genes and environments interplay to shape loneliness and other developmental psychological relevant outcomes. This is a very welcome. However, when developmental psychology now is ready to integrate recent genetic and neuroscience knowledge and methods, I think it would be very wise to not uncritical go through the mistakes that have be done in other disciplines and instead learn from their hard lessons. I discuss some problems (genes versus environments, identifying gene for a phenotype, environments cause of developmental outcomes, and gene X environment interaction and epigenetics) and some suggestions for solutions which can be used to avoid throwing in the bathwater with the baby.