This link has been suspected for some time, but Professor Keith Kelley, president of the PsychoNeuroImmunology Research Society (PNIRS), says that this area of research is finally being taken seriously. "Fifteen years ago, talk that the mind affects the body was all hypothesis," he says. "Now scientists are demonstrating that physiological changes in the body do occur directly because of the way we feel."
Specific studies in this area have long been investigating emotions - along with the circumstances that triggered them - and their link with physical well-being. According to doctors, worrying, for example, can raise blood pressure, increase levels of destructive stress hormones and possibly the risk of cancer. According to Dr Edward Hallowell from the Hallowell Centre in Massachusetts, up to 25 per cent of the population have health problems caused by something he calls "toxic" worry - worrying for the sake of worrying.
Feeling you lacked parental love also puts you at increased risk of a whole host of health problems including high blood pressure, ulcers and heart disease. A Harvard University study asked 126 young men to say how close they were to their parents. Thirty-five years later, a study examined their medical records and found that 91 per cent who did not perceive themselves to have a good relationship with their mothers and 82 per cent of those who scored badly on closeness to their fathers had developed serious conditions in later life, as compared with 45 per cent of those who felt they had a good parental bond.
Our relationships can have devastating consequences on health, too. A study of divorced couples found that the partner who hadn't wanted the divorce had a reduced immune system compared with the partner who did. Another study showed that men who don't think their wives love them are more prone to developing ulcers five years down the line. Meanwhile, anyone having an extra-marital affair should perhaps think twice. Research by Dr David Warbuton discovered that people who say that they regularly feel guilty have a more depressed immune system than those who don't.
In his latest book, Love and Survival (published by Vermilion, price pounds 9.99), Dr Dean Ornish, one of the world's leading heart researchers, says that feelings of loneliness and isolation in general have been shown to "increase the likelihood of disease and premature death from all causes by between 200 to 500 per cent".
The figures - and the huge volume of research on both sides of the Atlantic that back up the findings - are impressive. But why do doctors think the link between mind and body is so strong? Dr Candace Pert from Georgetown University in Washington DC has been studying the effects of our emotions on our health for more than 20 years. She believes that our feelings can "quite simply determine whether you get sick or stay well". The key, she says, is the way we deal with our feelings rather than the feelings in themselves. She says that we need to deal with our emotions appropriately; that is, to process them properly and work through them effectively in order to avoid knock-on health problems.
Dr Pert says that if we could monitor the chemical content of the body we would see that it was endlessly trying to retain what she calls "balance". "The immune system, the hormones and the brain are in constant communication altering our temperature, our cell levels, how much air we need to take in etc, in order to keep the correct balance according to our needs," she says. So, for example, if you've got a healthy attitude to stress there won't be a problem. "Your body kicks in with adrenalin to speed things up in case you need to run away, endorphins to keep your mood up and hormones to stop your stomach digesting because, let's face it, when you're stressed out food is the least of your worries." Once the stressful period is over, the body switches off again.
But if you're bad at dealing with pressure your body goes into overdrive and doesn't know how to get back to "normal". Dr Pert continues: "An emotion is basically a series of chemical reactions that trigger your body to react in a certain way - the way your body believes is the appropriate way to deal with whatever is happening. You get sad you produce tears, you get angry you shout. If the emotion is dealt with correctly, the body rebalances - if, however, you suppress the emotions or overload your system with constant stressors, balance can't occur and your body is adversely affected."
Again specific research bears this out. "Studies have shown that long- term stress, for example, can alter the way that DNA is repaired in the cells," says Dr Pert, "a process potentially linked to the development of cancer."
The way we deal with anger is also significant according to researchers. The World Congress of Dermatology found that patients who developed psoriasis early in life were more likely to have internalised anger as children than non-sufferers. The Chicago Medical School also found that back pain sufferers who didn't deal with negative feelings during stress were more likely to suffer increased pain.
According to Dr Pert, the suppression of an emotion such as anger takes energy which could be used elsewhere. "For example, if this lack of energy means that 20 of the 200 or so chemicals your body produces are out of balance, that's 10 per cent of your body out of kilter."
Of course brooding over anger or stress doesn't automatically mean we're going to get ill. As Professor Keith Kelley says: "Stress in itself doesn't cause illness - microbes do." But the way we deal with stress might mean that the microbes have a better chance of taking hold.
The way our chemical messengers work is to bind with a receptor on the cell - sort of like a lock and key mechanism. "And this is exactly the same way that viruses enter cells," says Dr Pert, explaining that, for example,the cold virus enters a cell through the same "lock" as the transmitter neuroephidrine which is produced when you're excited. "Which is why you're unlikely to get sick before something you're looking forward to; the high levels of neuroephidrine in your body fill the cell receptor and prevent any cold viruses circulating from taking hold."
A common misunderstanding about PNI is that there's a way to think ourselves well - that if we get struck down by something serious it's possible for us to think our way out of it. "But that's an insult to anyone who has ever been beaten by a terminal illness," says Professor Keith Kelley. "It's like saying they didn't think hard enough." On the other hand he does think that keeping a positive outlook and a healthy mental attitude "can maximise the natural fighting power that your body has".
Bear in mind, though, that, according to Dr Pert, it's not about thinking happy thoughts at all times. "That would just be phoney and phoney thoughts throw the body out of balance as well." She recommends that instead we develop an approach of appropriate emotions. "A healthy mind is one with flexibility. There's no such things as `good' emotions or `bad' emotions, only inappropriate responses."
GET IT OUT YOUR SYSTEM
If you're relaxed you're less likely to catch flu
Negative feelings make you more prone to pain
Worry causes high blood pressure and increased risk of cancer
Lack of parental love can lead to ulcers and heart disease
Divorce and guilt depress the immune systemReuse content