Maternal and paternal smoking during pregnancy and the risk of ADHD in offspring: An umbrella review of systematic reviews and meta-analyses

Background: Prenatal exposure to maternal and paternal smoking has been investigated as a potential environmental risk factor for attention-deficit/hyperactivity disorder (ADHD) in offspring. Although many studies have examined these associations, the consistency and magnitude of the effect remain unclear. This umbrella review aimed to systematically evaluate and quantify the published evidence linking maternal and paternal smoking during pregnancy with ADHD risk in offspring. Methods: We conducted an umbrella review of systematic reviews and meta-analyses. We systematically searched PubMed, Scopus, PsycINFO, and Web of Science from inception to September 21, 2024, and screened reference lists from relevant articles. We included systematic reviews and meta-analyses of observational studies that assessed the associations between maternal and paternal smoking during pregnancy and ADHD in offspring. Eligible meta-analyses used categorical ADHD diagnosis criteria based on DSM or ICD or less rigorous criteria such as self-reports. We excluded non-human studies, primary studies, genetic studies, and conference abstracts. We calculated summary odds ratios (ORs) with 95 % confidence intervals (CIs), heterogeneity using the I2statistic, 95 % prediction intervals, small study effects, and excess significance bias. Quality was assessed using the AMSTAR-2 tool. This study is registered with PROSPERO, number CRD42022361466. Findings: From 2495 articles, six were eligible, yielding six meta-analyses that included a total of 2,218,965 participants for maternal smoking exposure and 183,666 participants for paternal smoking exposure. Maternal smoking was associated with a significantly increased risk of ADHD in offspring (OR 1.71, 95 % CI 1.46–2.00), with significant heterogeneity (I2 = 79 %) and highly suggestive evidence (class II). Paternal smoking was also associated with a significantly increased ADHD risk (OR 1.36, 95 % CI 1.17–1.59), with moderate heterogeneity (I2 = 47 %) and convincing evidence (class I). Further analyses indicated substantial heterogeneity and potential confounding by familial factors. Conclusion: Both maternal and paternal smoking during pregnancy were significantly associated with an increased risk of ADHD in offspring. However, evidence from familial studies suggests that maternal smoking may be confounded by genetic and familial factors, underscoring the need for further high-quality research to establish causality. These findings highlight the importance of prenatal smoking prevention as a modifiable risk factor for reducing ADHD risk. © 2025 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license. http://creativecommons.org/licenses/by/4.0/