Psychiatric Disease in Relation to Physical Illness

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Formerly, psychiatrists were termed alienists, as though they dealt with strange, alien phenomena that had nothing to do with the rest of us. People with psychiatric disease were either ignored, sometimes tolerated, but more often dealt with by incarceration in large institutions away from cities. The kind of mental illnesses found in these hospitals were the severe variety. Today we call them the psychoses (madness) and the dementias (cognitive disorders). To the public these disorders were undoubtedly strange, but they were studied extensively by those in the mental health movement in the nineteenth and twentieth centuries in North America and Western Europe. The illnesses were roughly classified so that it was possible to make several advances. First, how common these diseases were in terms of type and severity by standard demographic variables; second, how common milder forms of mental illness were (those were not admitted to hospital); and third, how these psychiatric disorders related to the so-called physical illnesses.


The science of epidemiology deals with the frequency of diseases in the community. The term incidence means "new cases" and prevalence means "all cases," new and old. So prevalence is incidence times duration. Psychiatric disorders have large prevalence rates mainly because they start in younger people, except for the so-called dementias like Alzheimer's disease. These psychiatric disorders are chronic or intermittent throughout life. A definitive study on these disorders was the Epidemiologic Catchment Area (E.C.A.) study, which was carried out in the United States around 1980 and published in detail in 1991 (Robins and Regier). This showed that 20 percent of all Americans had a mental illness at any one time and 32 percent at some point during their lifetimes. Depression and anxiety were common. Men had more mental illness than women, especially due to their having more substance abuse and antisocial personalities. Women tended to have more obsessive-compulsive disorder, major depressive disorder, and somatisation disorder (presenting psychological problems with physical symptoms). Perhaps the most interesting finding was that depressive illness declined with old age. The finding was counterintuitive since it is often thought that elderly persons have sad lives due to loss of status, income, marriage partners, and health. Other studies in different parts of the world have, however, confirmed the finding; yet it remains much argued. The arguments against the finding are that elderly persons tend to express psychiatric illnesses in physical terms, and so their true nature may be missed; and if all the different kinds of depression are added up the result is as high a rate for elderly persons as for the middle aged.

The E.C.A. study indicated that there was considerable comorbidity, that is, simultaneous occurrence of different psychiatric disorders and, separately, physical diseases. There was a tendency for those with psychiatric diseases to come from disadvantaged backgrounds. In other words, rates were higher among those who failed to complete high school, those on welfare, the unemployed, the unskilled, and the single. Thus, lower socioeconomic status is an important factor in mental illness. At the same time it should be remembered that the same applies to physical illness. So poverty, or relative poverty, plays a part in physical and mental illnesses, both helping to cause them and resulting from them. A more recent U.S. study, looking specifically at comorbidity, found even higher prevalence rates: almost half of the population studied (48 percent) had a psychiatric illness during their lifetimes and almost a third (29 percent) were ill at any one time.

The clinical conundrum

So on the psychiatry side we see that these disorders are exceedingly common. More common than diseases like arthritis, diabetes, and asthma, with which we are all familiar. What is the public health significance of these mental disorders? As noted earlier, depression is significantly associated with lower socioeconomic status. But there is also a very important correlation with physical disease. This is what is called the clinical conundrum (Eastwood). This says that while psychiatric disorders, usually depression or anxiety, often present with physical complaints there is, indeed, a true excess of physical ailments and premature death among psychiatric patients. In other words, patients who are depressed may go to the doctor and say that they have an upset stomach or headache, and the doctor may take this at face value. He will attempt to evaluate the patient, by taking a history and carrying out an examination, and put the symptoms into some physical disease context. If this fails he may tell the patient that there is nothing wrong with him so the patient continues to have his psychiatric disorder, which the doctor fails to recognize. This is a terrible state of affairs, although too common, and leaves the patient depressed and/or anxious and not knowing what to do.

So it is important that the presentation of psychiatric illness is recognized for what it is. A patient may have an affective illness, anxiety, or depression, and present with so-called somatic symptoms; or may be hypochondriacal; or may have psychiatric symptoms as an overlay to preexisting physical disease. Elderly patients may suffer from delirium. This is a condition where the patient is temporarily confused, due to such causes as too much medication or infection. It can be seen that there is a complex intertwining of physical and mental illnesses in their presentations. Beyond that there is outcome. The clinical conundrum says that not only are the psychiatrically ill misdiagnosed but they actually carry more risk for physical diseases. This can be understood in terms of risk for certain physical diseases and/or risk of premature death. At one time certain diseases were labelled as being "psychosomatic." This was intended to mean that such diseases were specifically caused by "stress." These were diseases like peptic ulcer, diabetes, hypertension, and rheumatoid arthritis. This kind of simplistic thinking is now viewed as naive. All diseases are a complex mixture of genetic risk and environmental hazards. Epidemiology, by means of cross-sectional and longitudinal studies, has successfully examined the mind-body relationship. Early studies from mental hospitals, in a variety of countries, showed that patients had more diseases, such as tuberculosis, than might be expected. These could lead to premature death from so-called natural causes. In addition, these patients had more "unnatural" deaths from suicide. Community studies, which were carried out later, and were much more sophisticated, however, came up with the same results. An example is the Stirling County study, in Nova Scotia, Canada, which has followed a community sample since 1952 (Murphy et al.) The patients with depression, particularly males, carried a significantly greater risk of premature death, especially from heart disease. So not only do the mentally ill contract more physical diseases in general, but more specific diseases. Depression and vascular disease, for example, appear to be intimately and reciprocally related. Thus 20 percent of patients who have had a heart attack develop depression, as do 50 percent of patients who have had a stroke. This is the case after controlling for vascular risk factors. So depression may be an independent risk factor for vascular disease and vice-versa. One explanation for less depression being found in elderly persons is that the depressed have died in middle age from vascular disease. Clearly, with advancing age, and especially in great (very old) age, the relationship between mental and physical illness becomes more complicated. Everybody succumbs to physical disease prior to death, but not every elderly person has a mental illness. Curiously, those with Alzheimer's disease are frequently and, ironically, physically well. We do need to know more about depression. Women carry twice the burden of risk for depression as men, yet men get more heart disease and more often commit suicide. Life events, early life experiences, and being separated or divorced are important factors associated with depression. The Cross National Collaborative group study found that the prevalence of depression varies from country to country; that mood disorders are becoming more common and starting earlier in life; and that only about 15 percent get treated, even in the most advanced countries.

The global burden of disease

Finally, Murray and Lopez, working with The World Health Organization and the World Bank, have described the "global burden of disease," as a reference to the death and disability for the six billion people on Earth. They found that heart disease, which is related to depression, was the most common cause of death; suicide was the twelfth (highest among elderly, white males); cirrhosis of the liver and lung disease were thirteenth and sixth, respectively (think of the role of drinking and smoking in mental illness). Major depression was found to be the most common disabling disease. The world's top three causes for DALYs (disability adjusted life year) were heart disease, major depression, and stroke. These findings show how important psychiatric disease is in relation to physical illness worldwide.

Robin Eastwood

See also Bereavement; Delirium; Dementia; Depression; Disease Prevention; Geriatric Psychiatry.


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Murphy, J. M.; Monson, R. R.; Olivier, D. C.; Sobol, A. M.; and Leighton, A. H. "Affective Disorders and Mortality: A General Population Study." Archives of General Psychiatry 44 (1987): 473480.

Murray, C. J. L., and Lopez, A. D., eds. The Global Burden of Disease: A Comprehensive Assessment of Mortality and Disability from Diseases, Injuries and Risk Factors in 1990 and Projected to 2020. Cambridge, Mass.: Harvard University Press, 1996.

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Psychiatric Disease in Relation to Physical Illness

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