A groundbreaking theoretical review paper shows that some forms of depression may result from malfunctioning brain cells, termed microglia.

Hebrew University of Jerusalem researchers say that diseased microglia can cause depression and drugs that restore the normal functioning of these cells can be effective as fast-acting anti-depressants.

“However,” says Prof. Raz Yirmiya, director of the Hebrew University’s Laboratory for PsychoNeuroImmunology, and senior author of the journal’s paper, “this does not mean that all sub-types of depression or other psychiatric diseases are originated by abnormalities in these cells.”

Microglia, which comprise 10 percent of all brain cells, fight infectious bacteria and viruses in the brain. They also promote repairing and healing processes of damages caused by brain injury and trauma.

“Our views on microglia have dramatically changed over the last decade,” says Yirmiya. “We now know that these cells play a role in the formation and fine-tuning of the connections between neurons (synapses) during brain development, as well as in changes of these connections throughout life. These roles are important for normal brain and behavioral functions, including pain, mood and cognitive abilities.”

The study was recently published in the peer-reviewed journal, Trends in Neurosciences.

“Studies in humans, using post-mortem brain tissues or special imaging techniques, as well as studies in animal models of depression, demonstrated that when the structure and function of microglia change, these cells can no longer regulate normal brain and behavior processes and this can lead to depression,” Yirmiya says.

Yirmiya says the new research could have a profound impact on the future development of anti-depressant medications.

Co-authors of the paper were Neta Rimmerman, a post-doctoral fellow, and Ronen Reshef, a Ph.D. student in Hebrew University’s Department of Psychology.