Table 2. Meta-analysis results by type of age estimate, epigenetic clock and model.

Model of ADHD symptoms	Main		Extended
Age estimate	Beta (95% CI)	P value	Beta (95% CI)	P value
Gestational age, weeks
Clinically estimated GA	−0.04 (−0.07, −0.02)	0.00	−0.03 (−0.06, −0.01)	0.02
DNAm GA estimate
Bohlin	−0.05 (−0.09, −0.01)	0.01	−0.04 (−0.09, −0.00)	0.04
EPIC overlap	−0.05 (−0.08, −0.01)	0.01	−0.04 (−0.08, −0.00)	0.04
Knight	−0.01 (−0.04, 0.01)	0.26	−0.01 (−0.04, 0.01)	0.22
Epigenetic age acceleration
Raw EAA, weeks
Bohlin	0.04 (0.01, 0.08)	0.02	0.03 (−0.01, 0.07)	0.12
EPIC overlap	0.04 (0.00, 0.08)	0.03	0.03 (−0.01, 0.06)	0.18
Knight	0.02 (0.00, 0.05)	0.04	0.01 (−0.01, 0.04)	0.25
Residual EAA, weeks
Bohlin	−0.01 (−0.06, 0.05)	0.75	−0.02 (−0.08, 0.04)	0.52
EPIC overlap	0.00 (−0.01, 0.02)	0.87	0.00 (−0.02, 0.02)	0.97
Knight	0.01 (−0.02, 0.04)	0.42	0.00 (−0.02, 0.03)	0.84

Covariates included in the main model were child sex, cell-type proportions, and batch effects. In an extended model, maternal prenatal smoking, maternal alcohol consumption, maternal pre-pregnancy BMI, maternal highest education level attained, income, delivery method, maternal age at delivery, and parity were included as covariates on top of the main model covariates. Bold numbers indicate statistically significant results.