In his initial studies during the early 1990s Yirmiya demonstrated that
psychoactive drugs, particularly
alcohol and
opiates, modulate immune functioning and resistance to
cancer via brain-to-immune communication pathways. After establishing his laboratory in Jerusalem, Yirmiya focused on the implications of immune-to-brain signaling and using
animal models of various
infectious,
autoimmune and
neurological diseases he established the relationships between brain inflammatory cytokines and sickness behavior symptoms. He is specifically known for providing the first experimental evidence for a relationship between immune activation and major depression. His contribution was described in a historical review by Robert Dantzer and Keith Kelly, Who stated: "Raz Yirmiya was the first
psychobiologist to draw the analogy between sickness behavior and depression. He showed that rats treated with cytokines are less sensitive to the rewarding properties of a
saccharin solution or to the presentation of a sexually-active partner. Some of these deficits can be prevented by chronic but not acute administration of
antidepressant drugs that have little or no beneficial effects on sickness behavior." In parallel studies, Yirmiya employed unique controlled and prospective experimental
models of disease in humans, demonstrating that immune challenges, such as
endotoxin administration,
rubella vaccination or minor
surgery, induce cytokine-mediated disturbances in behavioral, emotional and cognitive functions. Together, these studies directly contributed to the formation of novel conceptualizations and the development of clinically effective treatments for inflammation-associated major depression. In recent years, Yirmiya discovered that microglia cells and pro-inflammatory cytokines in the brain play a critical role in normal neuro-behavioral processes, including
hippocampal-dependent memory consolidation,
neural plasticity,
neurogenesis, and the
modulation of these processes by environmental enrichment. On the other hand, disturbances in the structure and functioning of microglia cells and
pathophysiological levels of the inflammatory cytokine
interleukin-1 in the brain underlie the impairments in cognition and neurogenesis associated with
stress. and neurodegenerative diseases, as well as the development of depression. Yirmiya also discovered (together with Itai Bab from the Hebrew University of Jerusalem), the existence of brain-to-bone communication pathways, mediated by the
sympathetic and
Parasympathetic nervous system, and reported that chronic stress-induced depression produces bone loss via modulation of these pathways, forming the foundations of a new field of research that we termed "NeuroPsychoOsteology". Raz Yirmiya is a past-president of the Psychoneuroimmunology Research Society (PNIRS) He was an Associate Editor of Brain, Behavior, and Immunity (
Elsevier Press) and a recipient of the
Norman Cousins Award for outstanding contributions to research in psychoneuroimmunology. ==References==