Highly read on www.pnas.org in April
Long-term stress boosts inflammation, making people more susceptible to colds.
Sheldon Cohen at Carnegie Mellon University in Pittsburgh, Pennsylvania, and his team quarantined 276 volunteers and then exposed them to a rhinovirus that causes the common cold. People who had recently been experiencing a threatening stressful event were more likely to develop a cold than those who had not experienced stress. In the stressed individuals, white blood cell numbers did not correlate with levels of the hormone cortisol — indicating that the cells were insensitive to cortisol's anti-inflammatory effect.
In another study of 79 volunteers exposed to a rhinovirus, those with cortisol-insensitive white blood cells had higher nasal levels of immune-signalling molecules that promote inflammation. The results suggest that stress induces cellular resistance to cortisol, reducing the body's ability to regulate inflammation — which is at the root of many diseases, including heart disease.