Associations with child ADHD
Overall, 323 (5.1%) children had ADHD; the cumulative incidence is shown in Figures S3-S4. The incidence rate was highest at age 7-10 years, and in boys (Tables S4-S5). The mean follow-up time was similar across the exposure groups (SSRI/SNRI exposed: 10.7 years (sd: 2.2); non-medicated: 10.9 years (sd: 2.2); discontinuers: 10.7 years (sd: 2.2)).
After weighting, the averaged hazard for ADHD reduced substantially in SSRI/SNRI ever in-utero exposed compared with non-medicated (wHR: 1.07, 95% CI: 0.76-1.51), but remained elevated when discontinuers acted as comparator (wHR: 1.53, 95% CI: 0.77-3.07). There was satisfactory balance of covariates between ever SSRI/SNRI-exposed and unexposed (Figure S5) after weighting, and the weights had acceptable characteristics (Table S6).
There was no association between SSRI/SNRI exposure in mid- or late pregnancy and child ADHD, relative to both comparators (Table 2), albeit the estimated 95% CI were imprecise. In the duration analyses, the ADHD hazard was of smaller magnitude for SSRI/SNRI exposure in 1-8 weeks (7-50% increased hazard) relative to 9-20 weeks (40-113% increased hazard). There was no clear duration-response relationship (Table 2).