A new animal study suggests that psychological stress may impair the function of blood stem cells through a complex communication pathway linking the brain, gut, and bone marrow.

Researchers used a chronic stress model in mice to investigate how prolonged psychological stress affects the immune system. Lead investigator Meng Zhao, a professor at Sun Yat-sen University, said the idea stemmed from a common observation: people experiencing long-term stress appear to become more susceptible to illnesses such as the common cold.

The study found that chronic stress reduces the self-renewal capacity of hematopoietic stem cells—the cells responsible for producing all blood cells—and decreases the production of lymphocytes, key components of the immune system.

The researchers also uncovered an unexpected biological pathway. Under chronic stress, the brain activates the sympathetic nervous system, which in turn influences the gut. This alters the composition of the gut microbiota and reduces levels of beneficial metabolites, including spermidine, a naturally occurring compound associated with healthy aging and cellular maintenance.

As a result, hematopoietic stem cells lose their ability to effectively sustain blood formation and immune function.

The team further discovered that chronic stress suppresses the activity of specific brain regions involved in the stress response. Experimentally inhibiting these same brain areas in mice produced similar defects in immune function.

According to the authors, the findings may provide the first direct evidence that specific brain regions can regulate the activity of bone marrow stem cells.

Independent experts who were not involved in the study described the findings as significant but cautioned that the research was conducted exclusively in animals. It remains unclear whether the same biological mechanism operates in humans.

The researchers now plan to investigate whether a similar brain–gut–bone marrow axis exists in humans and whether it contributes to aging, cancer, and other chronic diseases.