Psychiatric disorders are polygenic. The evidence is strong that many genes are involved in the etiology of AD (currently evidence of rare exonic, rare SV, and common variation), ALC (currently evidence of common variation), ASD (currently evidence of de novo exonic variation and SV), BIP (currently evidence of common variation), NIC (currently evidence of common variation), and SCZ (currently evidence of rare SV and common variation). Projections for ASD and SCZ suggest that variation at hundreds of different genes will ultimately be shown to be involved. 58,80,85 There are statistical hints that ADHD and MDD might also be polygenic.
