Abstract
BACKGROUND: Previous research has found that maternal stress during pregnancy increases the risk of offspring asthma. However, whether this association is consistent with a causal interpretation has never been tested. The objective is to determine whether there is a critical exposure period for maternal depression or anxiety on offspring asthma or whether cumulative exposure is most important, and to investigate evidence of confounding. METHODS: The study population included all children born in Sweden from July 2006 to December 2009 (n = 360 526). Information about childhood asthma, maternal depression or anxiety (diagnosis or medication) and covariates was obtained from the Swedish national health registers. The associations between exposure periods (pre-conception, pregnancy, postnatal or current) and childhood asthma were estimated using structured life course approach hypothesis testing. Paternal and cousin analyses were used to test for evidence of confounding from shared genes and environment. RESULTS: For childhood asthma, cumulative exposure best described the effect of exposure to maternal depression or anxiety up to a maximum of any two exposure periods [adjusted odds ratio 1.44, 95% confidence interval (CI) 1.38, 1.52]. The hypotheses of a critical period were not supported. The paternal and cousin analyses indicated minimal influence from familial confounding. CONCLUSIONS: These findings support an association between cumulative exposure to maternal depression or anxiety and asthma development in offspring. This association is unique for maternal depression or anxiety and not due to familial confounding. The clinical implication is that effective psychological management of women with chronic distress may reduce offspring asthma risk.