Previous studies have shown that the cognate ligand of RXFP3, relaxin-3, plays regulatory roles in appetite, arousal, memory, stress, anxiety and depression [19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35], thereby making this receptor an attractive target for drug discovery. Here, RLN3 is linked to major depressive disorder.