People who feel well tend to live well. They have a better immunity against infections and lower susceptibility to ill-health. Stress and depression, on the other hand, are linked to poorer functioning of the immune system, weaker responses to vaccination and, overall, higher rates of morbidity. But how a healthy mind makes for a healthy body wasn't known. Now, by artificially stimulating the reward circuitry in the brains of mice, scientists in Israel have shown that one of the nerve pathways in the body - called the sympathetic nervous system - can directly manipulate the immune system. Claire Armstrong spoke to Dr Asya Rolls to hear how...