A genome-wide investigation of depression among individuals with and without irritability

Individuals presenting with both depression and irritability may constitute a different group of individuals with respect to those presenting without irritability, but their biological differences remain unknown. We aimed to identify genetic variants associated with depression among individuals with and without irritability, highlight biological pathways, and test for genetic associations with other traits. We conducted a genome-wide association study (GWAS) using data from the UK Biobank (N = 487,409). We identified a group of individuals presenting with depression and reporting never having experienced irritability (depression without irritability, n = 35,857, 11.8%), and another with depression and reporting having experienced irritability (depression with irritability, n = 23,613, 8.1%) and compared them to controls with no depression or irritability (n = 268,012). The GWAS of depression without irritability identified 2 SNPs which reached genome-wide significance (P < 5×10^-8; rs72795440 and rs1233494). The GWAS of depression with irritability (N_GWAS = 292,485) identified 3 SNPs reaching genome-wide significance (rs2815748, rs102275, and rs7227069). When comparing SNPs between depression phenotypes, 15 SNPs had significantly different effect sizes. Patterns of genetic correlation with 44 complex traits were overall similar between the 2 depression phenotypes, with the highest genetic overlap observed with anxiety for depression without irritability (r_g = .77) and neuroticism for depression with irritability (r_g = .76). This study shed light into common and distinct biological factors characterizing depression among individuals with and without irritability and contribute to better understanding the genetic architecture of depression to potentially inform treatment and personalized medicine.