Aim
Epidemiological studies on associations between Caesarean sections (C‐sections) and attention‐deficit hyperactivity disorder (ADHD) have been inconsistent, and we performed a meta‐analysis.
Methods
We systematically searched PubMed and Embase to December 2018 and included nine hospital‐based and population registry studies published in 2011‐2018. These covered a total study cohort of more than 2.5 million people in eight countries: Australia, Brazil, Denmark, Finland, Germany, Sweden, Turkey and the UK. The analysis provided summary odds ratios (ORs) and 95% confidence intervals (CI) while taking heterogeneity into account.
Results
We found that that C‐sections were associated with a small increase in the risk of ADHD (OR 1.14, 95% CI 1.11, 1.17, I2 0%) in offspring. In subgroup analyses, the association remained for both infants born after elective C‐sections (OR, 1.15, 1.11, 1.19, I2 0%) and emergency C‐sections (OR, 1.13, 1.1, 1.17, I2 45.4%). However, these were only marginally significant when we pooled data from siblings from other pregnancies (OR, 1.06, 1.00‐1.13, I2 0%), implying that the association was due to confounding.
Conclusion
The statistically significant association between C‐sections and ADHD in children can be partially explained by unmeasured confounding. Further research controlling for important confounders is required before firm conclusions can be drawn.