Background
Evidence on the association between paternal smoking and attention-deficit hyperactivity disorder (ADHD) in offspring is inconsistent. We conducted a systematic review and meta-analysis to synthesise the available evidence.
Methods
This meta-analysis was performed following the Preferred Reporting Items for Systematic Review and Meta-analysis guidelines. The review protocol was prospectively registered in the International Prospective Register of Systematic Reviews (PROSPERO). Pooled odds ratios with 95% confidence intervals (CIs) were calculated using a random-effects meta-analysis. The heterogeneity among studies was assessed using the I
2 test. Publication bias and the presence of small study effects were evaluated using funnel plots and Egger’s test. Sensitivity and subgroup analyses were also performed.
Results
Twenty observational studies involving over 294,236 study participants from 16 different countries were included. We found that paternal smoking was associated with a 22% increased risk of ADHD in children (RR = 1.22, 95% CI: 1.12, 1.33). Our subgroup analysis revealed that this association was not evident among studies that accounted for maternal smoking (OR = 1.14, 95% CI: 0.98, 1.33), paternal alcohol use (OR = 1.02, 95% CI: 0.79, 1.33) and education (OR = 1.14, 95% CI: 0.98, 1.34).
Conclusion
The observed association between paternal smoking and the increased risk of ADHD in children may be confounded by maternal smoking, paternal education and other shared familial and socioeconomic factors. Future studies should incorporate maternal–paternal comparisons to disentangle the independent and combined effects of parental smoking on ADHD risk in children, while more rigorously controlling for confounding.