Via Nature: Immunology: The pursuit of happiness, a November 27 report on the controversial field of psychoneuroimmunology. Excerpt:
In 1964, magazine editor Norman Cousins was diagnosed with ankylosing spondylitis, a life-threatening autoimmune disease, and given a 1 in 500 chance of recovery. Cousins rejected his doctors' prognosis and embarked on his own programme of happiness therapy, including regular doses of Marx Brothers films, and credited it with triggering a dramatic recovery. He later established the Cousins Center, which is dedicated to investigating whether psychological factors really can keep people healthy.
At the time, mainstream science rejected the idea that any psychological state, positive or negative, could affect physical well-being. But studies during the 1980s and early 1990s revealed that the brain is directly wired to the immune system — portions of the nervous system connect with immune-related organs such as the thymus and bone marrow, and immune cells have receptors for neurotransmitters, suggesting that there is crosstalk.
These connections seem to have clinical relevance, at least in the case of stress. One of the first researchers to show this was virologist Ronald Glaser, now director of the Institute for Behavioral Medicine Research at the Ohio State University in Columbus.
“When I started working on this in the 1980s, nobody believed what stress could do, including me,” he recalls. He and his colleagues sampled blood from medical students, and found that during a stressful exam period, they had lower activity from virus-fighting immune cells, and higher levels of antibodies for the common virus Epstein–Barr, suggesting that stress had compromised their immune systems and allowed the normally latent virus to become reactivated.
The field of PNI has grown hugely since then, with medical schools worldwide boasting their own departments of mind–body medicine, of which PNI is just one component. It is now accepted that the body's response to stress can suppress parts of the immune system and, over the long term, lead to damaging levels of inflammation.
Large epidemiological studies — including the Whitehall studies, which have been following thousands of British civil servants since 1967 — suggest that chronic work stress increases the risk of coronary heart disease and type 2 diabetes, for example.
Low socio-economic status increases susceptibility to a wide range of infectious diseases, and there is considerable evidence that stress increases the rate of progression of HIV/AIDS. But researchers have a long way to go before they will understand exactly how signals from the brain feed into physical health.