Immune system imbalances may cause depression – study

A recent analysis by an Israeli scientist shows that depression may start with an imbalance in the immune system. The research therefore questions long-held beliefs and opens the way to personalized treatment.

Traditional theories of depression have focused on neurotransmitters such as serotonin and norepinephrine, suggesting that a deficiency of these brain chemicals can lead to depressive symptoms. Although widely accepted, these theories did not explain why a large proportion of patients do not respond to conventional antidepressants.

Over the past 30 years, research by Professor Raz Yirmiya from the Department of Psychology at the Hebrew University of Jerusalem, along with other work, has pointed to another culprit: chronic inflammation, both some in the body and in the brain, he writes Medical News.

“In many people, depression is the result of inflammatory processes,” explained Professor Yirmiya, who was one of the first researchers to establish links between immune system deficiency and depression back in the 1990s .

His latest study, in fact a major review of 100 papers in the field, built on findings from the 1980s that showed depressed people often had impaired immune function.

Surprisingly, some immune-stimulating treatments for cancer and hepatitis, which cause an inflammatory response, have been found to cause severe symptoms of depression in patients, providing insight into the role of the immune system in their mental health.

The tests of Prof. Yirmiya further established a mechanistic link between inflammation and mood, showing that healthy people injected with low doses of immunostimulatory agents experience a temporary state of depression that can be prevented by anti-inflammatory treatments or current antidepressant.

He and his team also showed that stress – often a major cause of depression – can stimulate inflammatory processes, affecting the brain’s microglial cells, which are agents of the immune system in the brain.

Microglial cells are an integral part of the immune system and therefore the body, responsible for the protection of the central nervous system and the cleaning of plaques, damaged cells and other substances that must be removed for the proper functioning of the body .

The recent findings, published in the journal Brain, Behavior, and Immunityshow that stress-related inflammatory responses may initially activate microglia, but that prolonged stress eventually depletes and damages them, thereby maintaining or causing depression.

“This dynamic cycle of microglia activation and decline reflects the evolution of depression itself,” explained prof. Ermiya.

The findings highlight the need for anti-inflammatory therapies for some patients and microglia-stimulating therapies for others, suggesting that a personalized approach may be more effective than traditional “one-size-fits-all” antidepressant therapy. which is suitable for all”.

“Research findings from the last three decades emphasize the critical role of the immune system in depression. In the future, an approach based on personalized medicine – tailoring treatment to a patient’s specific inflammatory profile – may offer hope to the millions of patients who do not benefit from conventional treatments. By adopting these advances, we are not only treating the symptoms, but addressing their underlying causes”, concluded prof. Eirmiya.