Comorbidity of mental and physical disorders: a key problem for medicine in the 21st century

Comorbidity – the simultaneous presence of two or more diseases is undoubtedly one of the most important challenges to medicine of the 21st century. Our success in prolonging life expectancy did not greatly increase the number of disease-free years: the years gained are years in which people tend to suffer from a variety of chronic diseases, impairments and disabilities. The survival into higher age brought with it also a true, still not sufficiently well recognized, epidemic of comorbidity. The comorbidity of two or more somatic diseases – for example cardiovascular disease and diabetes – is generally recognized as being frequent and requiring simultaneous attention to both diseases. The situation is different when it comes to the comorbidity of mental and physical illness. Psychiatry has grown and developed without much linkage to general medicine or any of the other medical specialties. Oncologists and other specialists who deal with particularly lethal diseases are perhaps an exception – although even there, the co-existence of cancer and a mental disorder such as depression led to the development of a subspecialty – that of psycho-oncology – rather than to a close collaboration between oncology and mainstream psychiatry. In the late 19th century when many countries constructed mental hospitals, it was normal and expected that one of the departments or a pavilion will be reserved for the treatment of somatic illness of the in-patients. Frequently, the reason for placing a mentally ill person in such a ward was tuberculosis, but there were many who were suffering from other communicable or non-communicable disorders. Many of the mentally ill had a short life expectancy, died early because of neglect, physical hardships, poor access to medical care, and thus, there were not all too many people with mental and a physical illness. The ward for patients with comorbid physical illness were therefore usually of a modest size and rarely had more than 10% of the institution's beds. Gradually, the situation changed and medical departments in mental hospitals vanished. Better transport made it easier for medical specialists to come to the mental hospitals, and patients could be transported to the general hospitals for examinations and care. The diagnostic apparatus in mental hospitals, for example, for radiography grew obsolete and usually left to decay. At the same time, departments of psychiatry in general hospitals became more frequent. The public in many countries – and health administrators – increasingly perceived psychiatry as being distant from classical medicine. Psychoanalysis became better known and entered the public mind replacing previous images of psychiatry. Psychiatrists no longer made physical examinations at the beginning of their acquaintance with the patient. The psychiatry of the asylum with its inhabitants, forgotten by all miles away from other medical institutions, was not seen as dealing with the same kind of people as other medical institutions or for that matter with people with common mental disorders such as depression or anxiety treated in the psychiatric departments of the general hospital. Some psychiatrists still saw themselves as doctors and emerged as a subdiscipline of ‘liaison psychiatry’ indicating that they are linked with general medicine – a sad admission by the majority of psychiatrists (who did not claim to be liaison psychiatrists) that they did not feel interested nor competent to deal with mental health issues presented by patients who were treated for a physical illness. The situation is perhaps gradually improving. The excellent studies of mortality of people with mental illness undertaken in Scandinavia, Australia and elsewhere 1-4 made it gradually obvious that comorbidity of mental and physical disorders is frequent, deadly and growing. Physical diseases do not only kill people who suffer from mental illness: they also make their life even more difficult. The comorbidity does not only produce suffering. It also makes the cost of treatment of the participating diseases much higher than it would have been had these diseases appeared alone 5. Mental disorders still carry stigma, which makes access to care less easy and the quality of care less good – both of which contribute to the probability of complications of physical illnesses such as diabetes. It is still uncertain whether stigma and discrimination in health care and self-neglect often present in depressive and other mental disorders is the main reason for the higher likelihood of complications: recent findings of immunologists open the door to thinking that mental disorders such as depression perhaps share some of the aetiopathogenetic pathways with disorders such as diabetes affecting not only the likelihood of comorbidity but also that of complications. For all these reasons, it is of great importance to promote research into comorbidity and think of ways in which health care could be reorganized so as to facilitate treatment and recovery of people struck by comorbid mental and physical disorders. An important support to this effort is publications about comorbidity – such as that by Dickerson et al. 6 in this issue of Acta. Such publications will not only help to move research forward and towards new goals: they might also in time – and I hope soon – influences the education of health workers at undergraduate and postgraduate level. The current fragmentation of medicine into ever finer specialties makes the management of comorbidity ever more difficult: a reorientation of postgraduate training might improve the situation.