The Sickening Mind: Brain, Behaviour, Immunity and Disease

The sheer volume of animal research in this field makes it impossible to describe more than a tiny and rather haphazard selection of examples. And some of the experiments, especially those performed in the dim and distant past, are too grisly and unethical to deserve a mention. We humans are not the only animals whose physical health can be damaged by upsetting events.

The mind and the common cold

The way in which psychological factors can affect our susceptibility to disease is illustrated by research on that most mundane of illnesses, the common cold.

For centuries it has been widely believed that stress makes us more prone to minor respiratory infections such as colds and ’flu. This has now been confirmed experimentally. It is surprising that until recently much of the scientific evidence regarding the effects of psychological factors on respiratory infections was suggestive rather than conclusive.

In one study, for example, researchers asked married couples to fill in a questionnaire each day for three months, recording the various stresses and hassles of everyday life together with their state of health. The results showed that respiratory infections tended to be preceded by a greater than average degree of stress. Typically, a few days before the onset of symptoms there would be a rise in the number of unpleasant life events and a drop in the number of desirable events.

Much firmer evidence came from a pioneering experiment in which psychologist Richard Totman and colleagues infected healthy volunteers with cold-inducing rhinoviruses, having first assessed each individual’s psychological profile. It transpired that personality and previous exposure to stress had a significant bearing on both the risk of infection and the severity of the subsequent cold. Individuals with introverted personalities developed more severe colds, as did those who had experienced certain types of stressful life events.

The volunteers in this experiment were deliberately infected with viruses in order to avoid a potential ambiguity that had undermined previous research. Critics had pointed out that a correlation between psychological factors and colds could be attributed to varying degrees of exposure to cold viruses, rather than anything to do with biological resistance to infection. Individuals with shy personalities, say, or those who have recently experienced a traumatic life event, might be inclined to stay at home and would therefore have fewer opportunities to catch a cold.

By exposing all subjects equally to cold viruses Totman’s experiment excluded this possibility. The fact that psychological measures still predicted the clinical outcome implied a more direct link between mental state and disease.

The technique of deliberately exposing people to bacteria or viruses in order to assess their vulnerability had, incidentally, been used before. In one hair-raising experiment in the early 1970s a group of healthy (and obviously well-motivated) volunteers were exposed to bacteria which cause a plague-like disease, with symptoms including prolonged fever, vomiting, headaches and swollen lymph nodes. Two days before they were infected each subject’s stress level was assessed using standard psychological techniques. Those who registered the highest stress levels went on to have the most severe fevers.

Further compelling evidence for a connection between psychological stress and colds came a few years ago from a similar experiment. It is worth considering this experiment in detail because it illustrates some important general points.

Sheldon Cohen and colleagues recruited 420 healthy men and women and installed these worthy volunteers in residential accommodation at the British Medical Research Council’s Common Cold Unit in Salisbury. They then used standard psychological techniques to assess the mental state and stress level of each volunteer. Specifically, the researchers noted the life events that each subject had experienced over the previous year; the extent to which subjects perceived themselves as unable to cope with the demands placed on them by life; and each individual’s current emotional state. The volunteers were then exposed to a standard dose of cold viruses which matched the level of virus exposure one might expect to find in normal life. Each subject was given nasal drops containing one of five viruses capable of producing a common cold.3

Over the following week the subjects were monitored to see if they had been infected and, if so, whether they then developed clinical symptoms of a cold. Each day a doctor examined them for signs and symptoms of a cold using a standard checklist.4 (So this experiment, you will notice, was immune from the criticism that stress might have affected the subjects’ sickness-related behaviour as opposed to their actual health.)

The results of Cohen’s experiment were clear and compelling. The more psychological stress an individual reported having been exposed to in the past, the greater their chances of infection with cold viruses and, once infected, the greater their chances of developing a clinical cold. Both the risk of viral infection and the risk of developing clinical symptoms increased in direct proportion to the amount of stress.

The correlation between stress, infection and illness was impressively strong. Individuals with the highest stress ratings were six times more likely to be infected with cold viruses than those with the least stress, and twice as likely to develop a cold. Moreover, these associations between stress, infection and illness held up even after the data had been adjusted statistically to remove any effects of other potentially relevant factors, including the subjects’ age, sex, prior health, allergies, smoking and drinking habits, sleep and exercise patterns, diet, weight and education.

The technique of deliberately exposing the subjects to viruses ensured that they all had an equal opportunity to be infected. But you can be exposed to viruses without being infected. When you travel in a crowded train or bus you are regularly showered with exotic bacteria and viruses, but fortunately infection does not inevitably follow. Most of the time the bugs fail to make it past your skin or penetrate your inhospitable orifices. To establish that you have actually been infected it must be possible to recover viruses from your blood or body fluids, or show that your immune system has generated antibodies against the virus.

Exposure to viruses and subsequent infection are not the only steps along the path to illness, however. Not every infection develops into a clinical disease. The number of colds you will suffer in a lifetime represents a minuscule fraction of the number of cold virus infections you have had.

Detailed analysis of this experimental data enabled Cohen and his colleagues to tease apart the influences of stress on these two distinct components of disease. Whether or not someone was infected by the cold viruses depended primarily on how they were feeling at the time, especially their current perception of stress and negative emotions. But once they had been infected their chances of going on to develop a clinical cold depended more on their previous exposure to stressful life events than their current emotional state.

These results illustrate a general point: an individual’s psychological state can exert different influences on the various steps in the pathway to disease, from initial exposure to disease-causing viruses or bacteria, through infection by those viruses or bacteria, to the development of disease symptoms and the behavioural response to those symptoms.

We have sampled some of the extensive evidence that what goes on in people’s minds really does affect their chances of becoming ill or dying. The next question is how. It is time to consider the question of mechanism.

3 Psyche’s Machine: The Inside Story

Her pure and eloquent blood

Spoke in her cheeks, and so distinctly wrought,

That one might almost say, her body thought.

John Donne, Of the Progress of the Soul,

‘Second Anniversary’ (1612)

By what means does the mind influence human susceptibility to disease? How can insubstantial thoughts or emotions produce a cold, let alone heart disease or cancer? After all, colds are caused by viruses not thoughts. We have seen evidence that our mental and physical states affect each other; what we need now is an explanation of how they do this. We need a mechanism.

In this chapter we shall explore the biological and psychological pathways by which the mind influences physical health – and, as we shall see, how physical health in turn influences the mind. This is the inside story of how the mind and body interact. There are three main strands to this story. First, our minds can make us believe we are ill, whether or not we really are ill in any objective, clinical sense. Our psychological and emotional state affects our perception of bodily symptoms and our reaction to those symptoms. This is the familiar (and generally misleading) connotation behind terms such as ‘psychosomatic’. But the mind does more than influence our perception of physical wellbeing: it can genuinely affect our physical health. We come now to the second and third strands of the story.

The mind impinges on physical health in two fundamentally different ways: through our behaviour and, more directly, through our body chemistry. Psychological and emotional factors can lead us to behave in unhealthy or self-destructive ways which increase the risks of disease, injury or death. Smoking is an obvious example. Meanwhile, beneath the surface, our mental state can alter our susceptibility to disease by influencing the body’s biological defence mechanisms, most notably the immune system.

The perception of sickness

There is a fundamental distinction between illness – the sufferer’s belief that something is wrong with them – and disease, which is a definable medical disorder that can be objectively identified according to agreed criteria. You can have a disease (such as early-stage cancer or coronary heart disease) yet not feel ill. Conversely, you can feel ill even though a doctor cannot detect any evidence of disease.

Many people who end up presenting themselves to a doctor have no identifiable organic disease. There is apparently nothing physically wrong with them. Yet they are still there in large numbers, claiming (and, in most cases, genuinely believing) that they are unwell. They are often referred to in rather loaded terms as ‘the worried well’. But the majority of those who are suffering from vague, undiagnosed illnesses are not malingering. They really do feel ill and their ability to lead a normal life may be significantly impaired.

According to a report by the Royal College of Physicians and the Royal College of Psychiatrists, as many as half of all those who present themselves as out-patients for ostensibly medical reasons are suffering from psychological problems. Although they have physical symptoms such as pains, palpitations or breathlessness they have no detectable physical disease. Doctors perhaps understandably focus on the physical symptoms rather than the psychological problems. One consequence is that huge amounts of time and money are wasted on diagnostic tests and treatments for elusive diseases.

A substantial proportion of patients – a fifth or more – prove very difficult for doctors to deal with. Either their illness cannot be diagnosed at all, or, when a diagnosis is proposed, they find it unacceptable. Their treatment, if any, is frequently ineffective and they keep returning to the doctor over and over again, distressed and dissatisfied. These are the so-called heartsink patients. To make sense of what is going on we must once again turn to the mind.

Health and illness lie along a continuum. Often the dividing line between the two is arbitrary, and as much a reflection of our perceptions and expectations as it is of our true state of physical health. Our psychological and emotional state affects our sensitivity to bodily symptoms, our perception and interpretation of those symptoms and, finally, our propensity to seek medical help – whether or not those symptoms reflect a genuine disease.

Those who seek medical care do so because they have noticed certain symptoms, concluded that these symptoms constitute a real or potential illness, and decided to take action. Each of these steps is open to psychological and emotional influences. Individuals differ enormously in the extent to which they monitor their own health; in their willingness to put up with pain, discomfort and worry; and in their readiness to do something about it. The processes that culminate in a decision to visit the doctor depend on factors that are unique to each individual, including their social and financial circumstances, personality, experience, cultural background and genetic make-up. A lot can also depend on their current psychological and emotional state.

When a person is stressed or anxious they may become preoccupied with their health. There is a greater likelihood that they will notice (or imagine) physical symptoms; interpret those symptoms as indications of disease; and become sufficiently anxious about them to visit a doctor. They may also be more in need of the personal attention that they are perhaps not getting from others.

The heightened arousal that accompanies anxiety can make subtle bodily symptoms more noticeable. Moreover, the physiological changes that often accompany anxiety, such as headaches, churning guts or palpitations, may be interpreted as symptoms of disease. The mind can unconsciously create a medical mountain out of a molehill.

Our own perceptions are not the only ones that matter when it comes to assessing our state of health. The perceptions of those around us can also play an important role. Social pressures can reinforce, or even create, the perception that we are ill.

Imagine you are under a lot of stress. (Perhaps you don’t have to imagine.) You have been told you are going to lose your job, your partner has left you and your personal finances are in meltdown. Unless you are exceptionally self-possessed your behaviour patterns will change noticeably. Perhaps you no longer relish the prospect of going for a drink with your friends; you feel depressed so you decline social invitations; you sleep badly and come to work looking tired; you are preoccupied with your problems and your performance accordingly suffers; you become irritable or keep bursting into tears; you go off your food and lose weight, or perhaps you turn to comfort feeding and pile on the calories instead.

Your friends and colleagues notice these changes and comment on them. They keep remarking that you don’t look well; it must be the stress; perhaps you should see a doctor. Come to think of it, you don’t feel too marvellous. Those headaches and the constant fatigue might be significant, and you have lost weight.

Before long you have convinced yourself that you are ill. You have certainly read enough magazine articles to know that stress is bad for your health. You take to your bed, or perhaps you trot off to see your doctor. To put it in the language of social psychology, social pressures have encouraged you to take on the ‘sick role’. Now, you may indeed be genuinely ill; as we shall see, there is no doubt that stress can make us more susceptible to disease. But the thought processes that have led you to the conclusion that you are ill were driven largely by social pressure. Other people’s minds, as well as your own, were involved in the process.

Consider, for example, the case of Colin Craven – the hypochondriac from hell in Frances Hodgson Burnett’s children’s classic The Secret Garden.

The obnoxious, bedridden Colin has been treated as an invalid, doomed to an early death, for all of his ten years. Everyone in Colin’s orbit unquestioningly accepts that he is destined to be a crippled hunchback – that is, if he lives at all. They continually reinforce Colin’s belief in his illness, reminding him of his weakness and urging him to rest. As one would expect, lying in bed all day has had a seriously debilitating effect on Colin’s muscles; on the rare occasions when he does get up he feels genuinely feeble.

The egregious brat lies in bed all day with the family retainers pandering to his every whim. The servants live in fear of Colin’s hysterical tantrums and dare not contradict him. The housekeeper privately recognizes that Colin is a victim of self-indulgence and hypochondria but would not dream of saying this to his face. To make matters worse, Colin’s doctor is next in line to inherit the family property should Colin die and is therefore less than objective about the child’s health. A London doctor who has had the temerity to suggest that Colin is not ill has been studiously ignored. Colin is immersed in his all-consuming hypochondria and sublimely unaware of how spoilt and unreasonable he is. Until his cousin Mary arrives.

Mary (who is not the nicest of children herself) rubbishes Colin’s alleged medical condition during a fit of pique. She tells Colin bluntly that he has no trace of a lump on his back and is just being hysterical.

By challenging the unquestioned belief in Colin’s illness, Mary has an electric effect on him. The supposed invalid soon comes to realize that there isn’t anything wrong with him beyond his morbid state of mind. There is no lump on his back; he is thin and pallid because he refuses to eat properly; and he is weak because he lies in bed all day.

So long as Colin shut himself up in his room and thought only of his fears and weakness and his detestation of people who looked at him and reflected hourly on humps and early death, he was a hysterical, half-crazy little hypochondriac who knew nothing of the sunshine and the spring, and also did not know that he could get well and stand upon his feet if he tried to do it. When new, beautiful thoughts began to push out the old, hideous ones, life began to come back to him, his blood ran healthily through his veins and strength poured into him like a flood.

With the help of cousin Mary, her rosy-cheeked proletarian chum Dickon and, of course, the Secret Garden, Colin is soon transformed into a ‘laughable, loveable, healthy young human thing’ who announces to the world that he is going to ‘live for ever and ever and ever’.

A more delicate literary example of an indeterminate illness born of circumstance can be found in Tolstoy’s Anna Karenin. Young Kitty Shcherbatsky declines an offer of marriage from the worthy but unworldly Levin, expecting instead to receive a proposal from the dashing Count Vronsky. When Vronsky’s anticipated proposal fails to materialize, Kitty, like a good nineteenth-century heroine, goes into a severe physical and mental decline which lasts for months. It is serious stuff and everyone is worried about the poor girl’s health. Kitty’s family doctor discusses her condition with a celebrated specialist whose help has been enlisted by the worried family:

‘But of course you know that in these cases there is always some hidden moral and emotional factor’, the family physician allowed himself to remark with a faint smile.

‘Yes, that goes without saying’, replied the celebrated specialist …

Kitty’s family and friends are worried even though they are well aware that her condition has essentially psychological origins. Kitty is described as ‘ill for love of a man who had slighted her.’ Kitty’s health does not improve and it is feared that she might actually die. Her anxious parents therefore take her on a foreign tour, where she encounters another young lady whose illness is also ‘due to a love affair’. The passage of time and the distractions offered by foreign travel eventually bring about Kitty’s recovery. Her illness and absence also allow circumstances to develop in her favour; she returns to Russia, marries the faithful Levin and (unlike the eponymous Anna) lives happily ever after.

Another way in which mental processes intrude into the domain of physical health is through the universal need for legitimacy. When we have decided that we are ill we want other people, and especially our doctor, to accept that we really are ill and not just malingering or being neurotic. Whether consciously or unconsciously, we want our putative disease to be accepted as genuine and not dismissed as a product of our fevered imagination. We need to legitimize our sickness by presenting the doctor with symptoms that will be accepted as evidence of a known organic disease. After all, no diagnosis means no treatment. As we saw in chapter 1, this can be a real problem for those suffering from poorly understood and controversial disorders such as chronic fatigue syndrome.

In his fascinating historical study From Paralysis to Fatigue, Edward Shorter has described how the physical symptoms that characterize so-called psychosomatic illnesses – those vague, undiagnosable ailments whose physical causes prove so elusive – have evolved over the years to keep pace with changing ideas about what constitutes a genuine disease. As society’s perceptions and beliefs about disease have changed, so the symptoms of psychosomatic illness have also changed to keep pace with what is regarded as legitimate evidence of disease. Thus, in the eighteenth and nineteenth centuries it was common for people to succumb to hysterical paralysis, convulsions or ‘fits of the vapours’. Paralysis of the legs was positively de rigueur among well-to-do young ladies of the nineteenth century. Nowadays, some would regard the symptoms of chronic fatigue and allergies as falling into the same category.

Shorter’s historical analysis is interesting in that it demonstrates the powerful effect social pressures and cultural norms can have on patterns of symptoms. Actual diseases are another matter, however. There is nothing imaginary or unreal about many cases of chronic fatigue syndrome, allergies or other supposedly fashionable illnesses.

Our expectations also have an important influence on our perception of health. In industrialized societies like Britain and the USA general expectations of health have risen considerably in recent decades and continue to rise. As in so many other spheres of human activity, a consumerist attitude towards health has become the norm. People demand more in terms of their physical and mental wellbeing and are less willing to tolerate minor health problems which detract from their quality of life. That elusive – and probably illusory – gold standard of total health is increasingly demanded as of right even though, to quote one expert, ‘deviance, clinically or epidemiologically defined, is normal’. This emphasis on positive health, as opposed to the mere absence of disease, is reflected in the explosion of interest in complementary or alternative medicine.

Huge advances in living conditions and medical knowledge have brought about large increases in life expectancy in many countries during the course of the twentieth century. Yet despite this we are apparently a sick bunch and getting sicker – if, that is, we define sickness in terms of perceptions and behaviour as opposed to objective measures of physical health.1 Studies conducted in the USA in the late 1920s found an average of eight reported episodes of sickness for every ten people surveyed over a period of several months, whereas in the early 1980s the comparable figure was twenty-one sicknesses: an increase of 160 per cent. If we define sickness as seeking medical attention then the average person nowadays is ‘sick’ more than twice a year, compared with less than once a year in the 1920s. To be sick is normal.

Of course, what has increased over the decades is not the true incidence of diseases: it is our sensitivity to aches and pains; our tendency to ascribe them to physical diseases; our reluctance to put up with them; and our readiness to seek expert medical care.