The software PRS-CS92 was used to process ADHD GWAS summary statistics and assign per-allele posterior SNP effect sizes. A European LD reference panel generated from the 1000 Genomes Project data (https://github.com/getian107/PRScs) was utilized. The following default settings were used for PRS-CS: parameter a in the γ-γ prior = 1, parameter b in the γ-γ prior = 0.5, MCMC iterations = 1000, number of burn-in iterations = 500, and thinning of the Markov chain factor = 5. Additionally, the global shrinkage parameter phi was determined using a fully Bayesian method. Plink v2.093 was then used to calculate individual-level ADHD PGS. Linear regression was used to test the association between ADHD PGS and neurocognitive phenotypes measured in the PNC. Age (at time of neurocognitive testing), age2, genotyping batch, sex, and the first 10 MDS dimensions were used as covariates. The neurocognitive measures were obtained using the Computerized Neurocognitive Battery (CNB), which consists of 14 tests in 5 domains: executive control, episodic memory, complex cognitive processing, social cognition, and sensorimotor speed. The battery has been described in detail elsewhere40. Additionally, association of ADHD-PGS with results from the Wide Range Achievement Test (WRAT-4)41 were analyzed. See Supplementary Note regarding transformation of the CNB measures.
