Given MD’s high polygenicity compared to less polygenic disorders like ADHD and BIP, there were large differences in the number of shared and unique ‘causal’ variants. For example, MD and ADHD shared the smallest number of variants (4.4K, sd=0.4K), with many more unique-MD variants (10.1K, 0.6K) than unique-ADHD variants (1.2K, sd=0.5K). While they were moderately correlated at the genome-wide level (rg=0.45, sd=0.011), shared variants were strongly correlated (rgs=0.93, sd=0.07). AIC differences indicated that this analysis was underpowered to provide precise estimates (supplementary results). Nonetheless, there would still be strong rgs even in a scenario of complete genetic overlap (rgs-max=0.72, supplementary methods). A similar, although less pronounced, relationship was evident between MD and BIP. LAVA results supported these findings. All five significantly correlated loci for ADHD and MD were positively correlated, while 20 out of 22 (91%) were positively correlated between MD and BIP.
