For example, in addition to comprehensive searches for polymorphisms in the relaxin-3 or RXFP3 genes that might result in altered neurotransmission and affective behavior; once suitably validated assays for human relaxin-3 peptide and/or RXFP3 protein levels are available, studies to determine whether these are altered in patients who suffer from depression and other mental disorders could be completed, as potential markers for dysregulation of relaxin-3/RXFP3 related signaling. Here, RXFP3 is linked to mental disorder.