Chunk #56 — STAR* METHODS — QUANTIFICATION AND STATISTICAL ANALYSIS — Examination of the Impact of Sample Size Imbalance on Genetic Correlations and Genomic SEM Results
We conducted several analyses to examine whether differences in sample size among the 8 disorders influenced the pattern of cross-disorder genomic relationships we observed. First, we note that while sample size will affect the precision of a genetic correlation estimate (ie standard error) it should not affect the magnitude of the estimate itself (Bulik-Sullivan et al. 2015). As shown in Data S1.2, there is no substantial relationship between the estimated genetic correlations and the effective sample sizes of the corresponding disorder pairs (p-value for the slope = 0.055 ). The slightly positive linear relationship appears to be driven by MD and its genetic correlation with the other four major psychiatric disorders (SCZ, BIP, ASD, ADHD), however, these estimates are generally consistent with previously reported ones when sample sizes are much smaller (except for ASD) (Brainstorm et al., 2018) (Cross-Disorder Group of the Psychiatric Genomics et al., 2013) (Data S1.3). Furthermore, the largest among all pairwise comparisons, such as those between SCZ-BIP, AN-OCD, and ADHD-AN, do not scale with sample size.
