SAFit-ligands provide the foundation for a mechanistically novel treatment of stress-related psychiatric disorders. FKBP51 and FKBP52 are proteins which regulate multiple cellular activities. Most importantly in the context of psychiatric diseases, they interact in an antagonistic manner with receptors for stress hormones in the brain. FKBP51 inhibits while FKBP52 enhances the activity of the glucocorticoid receptor, thus playing a major role in the regulation of stress responses.