Scientists have long cautioned that stress is bad for the heart, and a new study provides insight into precisely why. In the Lancet, researchers lay out a chain of events: When people feel stress, the amygdala area of the brain—it processes emotions such as fear and danger—fires up with extra activity to help them cope. The problem is that the amygdala sends a signal to bone marrow to generate more white blood cells, and those blood cells in turn cause arteries to become inflamed, explains the BBC. That inflammation can then result in heart attacks and strokes. Researchers based their findings on two studies, the larger of which tracked nearly 300 people for about four years. The pattern seemed clear: Those with higher amygdala activity were more likely to develop heart disease of some kind.
"While the link between stress and heart disease has long been established, the mechanism mediating that risk has not been clearly understood," says study leader Ahmed Tawakol of Massachusetts General Hospital and Harvard Medical School, per Live Science. A link between stress and higher activity in bone marrow and arteries had previously only been recorded in animals, but the new research suggests it applies to humans as well, reports Reuters. The takeaway: "Reducing stress could produce benefits that extend beyond an improved sense of psychological wellbeing," says Tawakol. Those at increased risk of heart disease should look into stress-reduction techniques, he adds. (Almost half of all heart attacks are silent.)