Sub-group and sensitivity analyses
To address possible bias by exposure misclassification, we replicated the main analyses for SSRI/SNRI ever exposure in a sub-sample of women enrolled in MoBa since 2004, and compared “truly SSRI/SNRI-exposed” with “truly unexposed” pregnancies, based on concordant exposure information between self-reported and prescription dispensation data. To document confounding by maternal pre-existing psychiatric illness, we estimated the independent association of this factor with child ADHD, and further adjusted the weighted effect estimates for SSRI/SNRI exposure by this covariate. To assess the robustness of the findings, we carried out additional sub-group and sensitivity analyses, as described in detail in the Supplement.
Up to 16.5% of the pregnancies had missing values in at least one of the sufficient confounders. Under the assumption that data were missing at random, we imputed incomplete data via multiple imputation with chained equation (ten replications).31-33 More detail is provided in the Supplement.