Prenatal smoking exposure and offspring stress coping in late adolescence: no causal link.
BACKGROUND
In utero exposure to tobacco smoking has been suggested to cause persistent alterations in cognitive functioning. We examined if mothers' smoking during pregnancy (SDP) is associated with long-term impairment in offspring stress coping and the causal mechanism behind a possible link.


METHODS
We used a large cohort (n = 187,106) of young males in Sweden (mean age = 18.2 years), who underwent a semi-structured psychological assessment in 1997-2006, including an evaluation of stress coping ability, as part of the compulsory military conscript examination. We compared differentially exposed siblings within nuclear families and cousins in extended families and used multilevel structural equation models to disentangle genetic from environmental contributions to the association between SDP and stress coping.


RESULTS
SDP and offspring stress coping was moderately strongly associated when comparing unrelated individuals [regression coefficient (b) = -0.38 on a nine-point scale; 95% confidence interval (CI) -0.40 to -0.36, P < 0.0001]. In contrast, it disappeared when siblings were compared (b = 0.11; 95% CI -0.01 to 0.23, P = 0.071). This familial confounding was entirely due to genetic influences.


CONCLUSIONS
SDP is an established risk factor for pregnancy- and birth-related complications. However, we found no long-term effect of SDP on offspring stress coping. Rather, the observed association was due to familial confounding of genetic origin; women prone to SDP also transmit genes to their children that are associated with poorer coping with stress.
Kuja-Halkola
Ralf
R
Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden. ralf.kuja-halkola@ki.se
D'Onofrio
Brian M
BM
Iliadou
Anastasia N
AN
Långström
Niklas
N
Lichtenstein
Paul
P
D000223:Adaptation, Psychological; D000293:Adolescent; D000294:Adolescent Behavior / Q000523:psychology; D000328:Adult; D015984:Causality; D015331:Cohort Studies; D005190:Family; D005260:Female; D006801:Humans; D008297:Male; D008423:Maternal Age; D008425:Maternal Behavior; D008889:Military Personnel; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects / Q000453:epidemiology / Q000209:etiology* / Q000523:psychology*; D012042:Registries; D012044:Regression Analysis; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects*; D013315:Stress, Psychological / Q000453:epidemiology / Q000209:etiology*; D013548:Sweden / Q000453:epidemiology; D055815:Young Adult