Numerous scientific studies indicate that inflammatory processes play a key role in the development of psychiatric disorders. One of the areas of particular interest is the interleukin 6/STAT3 signal transduction pathway, which is associated with depression, schizophrenia, and bipolar disorder. In a study published in leading journal Molecular Psychiatry, MedUni Vienna researchers led by Daniela Pollak from the Division of Neurophysiology and Neuropharmacology showed that STAT3 plays an important role in the serotonergic system as a molecular mediator for controlling emotional reactivity, thereby establishing a mechanistic link between the immune system, serotonergic transmission and affective disorders such as depression.