Attention-deficit/hyperactivity disorder (ADHD) is a common neurodevelopmental disorder in childhood. Exploring the risk factors for ADHD is helpful in preventing ADHD.
To explore the association between maternal smoking during pregnancy and the occurrence of ADHD in offspring.
PubMed, Embase, and Cochrane Library were searched from inception to May 2017 for studies.
Cohort or case-control studies in which the association between maternal smoking and ADHD in offspring were investigated were eligible if they included odds ratios (ORs), hazard ratios, or risk ratios and 95% confidence intervals (CIs).
Two investigators independently extracted data on definition of exposure and outcome, number of cases and total sample population, and potential confounders adjusted. Any dose-relationship data for smoking and ADHD risk were also extracted.
Fifteen cohort studies and 5 case-control studies with 50 044 cases and 2 998 059 participants were included. Smoking during pregnancy increased the risk of offspring ADHD (OR: 1.60; 95% CI: 1.45–1.76). The risk of ADHD was greater for children whose mothers were heavy smokers (OR: 1.75; 95% CI: 1.51–2.02) than for those mothers were light smokers (OR: 1.54; 95% CI: 1.40–1.70).
The limitations of our study included different assessment tools of ADHD and a lack of objective biological measures for maternal smoking.
With our meta-analysis, we provide evidence for an association between maternal smoking and offspring ADHD but do not solve the causality issues concerning potential confounding by other risk factors. More high-quality studies are needed to establish whether the association with smoking is causal.
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