The FKBP5 gene is associated with stress-related psychiatric disorders. Not only the gene itself, but also epigenetic changes are possible biomarkers for the long-term consequences of stress. The underlying mechanisms cannot yet be determined in humans. Previous research suggests that the mouse is a suitable model organism for investigating the influences of genetics, the environment and their interaction in brain tissue. Scientists have now provided the first evidence that epigenetic changes – crucial key elements for the regulation of genes – can also be investigated in the so-called humanized FKBP5 mouse model.