A lot of stress harms your immune system, but research is now showing that a little may actually improve it, writes Vikki Burns.
Is stress good or bad for you? Does it leave you more at risk of catching a cold or give you the boost you need to get going? The effects of stress on health could be all in the timing, according to recent research.
People experiencing long-lasting psychological stress have immune systems that don't respond as well to a potential infection as their more relaxed colleagues. However, the good news is that a short, sharp burst of stress may be just the tonic your immune system needs.
These contrasting effects of stress on vaccination are being investigated by my PhD students, Anna Phillips and Kate Edwards, in the school of sport and exercise sciences at the University of Birmingham. By using 'flu vaccines to imitate an infection, the researchers were able to measure how well a person's immune system works in a variety of different conditions.
It is also important for people to respond well to a vaccination in order to avoid getting sick in the future. People with low antibody levels after vaccination are less protected if they come across the real infection.
"Older adults who had experienced a bereavement in the year prior to receiving their 'flu vaccine had poorer antibody responses to influenza vaccination than those who had not lost a close friend or relative," says Phillips.
This could be particularly problematic as the natural ageing process already weakens the immune system of older people. However, even young, healthy people are not resistant to the negative effects of stress, she says. "Students who reported more relatively mild stressful events also had poorer antibody responses to influenza vaccination."
It seems, however, that a short burst of stress or exercise may kick-start your immune system to get ready for action. "From an evolutionary perspective, activating the immune system in response to stress may be sensible," says Edwards.
"A caveman wouldn't want to escape from the jaws of a lion only to succumb to an infection in his wounds. In the same way that the heart has evolved to beat faster when stressed to meet your energy demands, your immune system may have evolved to be more effective to protect you against possible infections."
The research has shown for the first time in humans that a short exposure to stress immediately before vaccination could lead to a better immune response. Before receiving an influenza vaccination, the participants were stressed using either a competitive mental arithmetic task or a moderate cycling exercise task.
Others were asked to just sit quietly to act as a comparison group. "Women who had completed the mental arithmetic or the exercise tasks had better antibody responses to the vaccine than those who simply rested," says Edwards. "These results are very preliminary," she warns. "But we are hoping to develop an intervention that can be used in a wider population."
The answer may come from a recent finding that more targeted exercise is beneficial for the immune response to vaccination. "We asked people to complete a weightlifting task using the arm in which they were to be vaccinated, causing mild inflammation in the area," she explains.
This appears to "prime" the immune system to respond to any infection or vaccination that it encounters. People who had exercised prior to the vaccine had a better immune response than those who had not exercised.
A simple exercise that improves immune response to vaccination would be a "very exciting prospect", Edwards believes.
It is hoped that a short, simple weight-lifting task can be developed suitable for use even in older or frailer people. This could help the vaccination protect you as well as possible. These complex interactions between stress and immunity occur via a network of nerves and hormones that connect the brain to each of the immune organs and even individual immune cells. Thoughts, feelings and experiences get translated into electrical signals that zap immediately to a particular part of the immune system or into slower moving chemical messengers that drift in the blood towards a range of different immune targets.
Whether these influences have positive or negative effects on your health depends on many different factors. However, in this case, it appears that, as with so many things in life, the influence of stress is all in the timing.
Dr Vikki Burns is a scientist from the University of Birmingham on placement at The Irish Times as a British Association for the Advancement of Science Media Fellow