Many human illnesses arise from the interaction of individual genes and environmental influences. Traumatic events, especially in childhood, constitute high risk factors for the emergence of psychiatric illnesses in later life. However, whether early stress actually leads to a psychiatric disorder depends largely on his or her genetic predisposition.

Research Group Leader Elisabeth Binder of the Max Planck Institute of Psychiatry examined the DNA of almost 2000 Afro-Americans who had been repeatedly and severely traumatised as adults or in childhood. One-third of trauma victims had become ill and was now suffering from post-traumatic stress disorder. The risk of developing post-traumatic stress disorder rose with increasing severity of abuse only in the carriers of a specific genetic variant in the FKBP5 gene. FKPB5 determines how effectively the organism can react to stress, and by this regulates the entire stress hormone system. The scientists hoped to cast light on the mechanisms of this gene-environment interaction by comparing modifications of the DNA sequence of victims who had not become ill with that of those who had.