Major Depression Linked to Brain Cell Activity

Medical Reviewer

Progress in understanding the role of biology in depression has been slow. The idea that abnormalities may exist in the functioning of nerve cells is at best a limited explanation. Our limited understanding is reflected in the unpredictable effects of antidepressants. These span the spectrum of effective, to moderately effective, to no effect at all. Recent research to come out from the Hebrew University of Jerusalem is pointing in a different direction and may have both theoretical and clinical implications.

Around 10 percent of brain cells have an immune function. These Microglia cells are an active defense against infections as well as providing repair and healing functions. Professor Raz Yirmiya, director of the laboratory for psychoneuroimmunology, believes that abnormalities in these cells result in major depression. His findings do not account for all sub-types of depression but they could point towards a radical re-examination of major depression and stimulate new treatments.

Microglia cells undergo changes in a variety of conditions associated with depression. These range from infection, injury, trauma and aging to autoimmune diseases like multiple sclerosis and degenerative diseases like Alzheimer’s.  When activated these cells get bigger and they secrete substances that result in inflammation of the brain. What is also interesting is that these same cells become activated when people are under high levels of psychological stress, a leading cause of depression.

Reported on the ScienceDaily website, Prof. Yirmiya commented that understanding of microglia has increased dramatically over the past few years. The cells influence the formation and fine-tuning of nerve connections over a lifespan. When these cells are activated they no longer regulate normal brain and behavior processes which, says Yirmiya, can lead to depression. New generations of drugs could be developed to either inhibit over-active microglia or stimulate them if their function is found to be under-active.


Hebrew University of Jerusalem. "New depression diagnosis and treatment." ScienceDaily. ScienceDaily, 22 October 2015. <>

See More Helpful Articles

6 Behavior Changes During Depression

Mild, Moderate or Severe Depression: How to Tell the Difference

10 Ways Depression will Change You

The No-Treatment Option for Depression