A report card on the utility of psychiatric diagnosis
Authors: Allen Frances
Journal: World Psychiatry (2016)

Controversy about the utility of medical diagnosis and its relation to treatment had its origin 2500 years ago. The two leading centers of medical practice were then located in the Greek colonies at Cnidus and Cos. They had together revolutionized disease theory by substituting a secular biological model of causation for the previous belief in divine punishment. But the two schools differed greatly when it came to diagnosis and treatment approach. At Cnidus, there was great emphasis on specific diagnosis and accompanying specific treatment. At Cos, under the influence of Hippocrates, the contrasting approach was that it is more important to know the patient who has the disease than the disease the patient has. Neither model is appropriate for all times and all patient presentations. The more we understand disease process, the more valuable is specific diagnosis and specific treatment. But too often in the history of medicine, theory and practice have extended a reach that far exceeded their grasp. Almost all medical theories have turned out to be false and many of the medical treatments they justified have turned out to be dangerous, sometimes deadly. Doctors have confidently bled their patients; purged them with emetics and cathartics; fed them with heavy metal poisons; made them hot and made them cold. That patients keep coming back for more provides proof of the power of the placebo effect and of the (sometimes excessive) trust accorded physicians. The recent miraculous advances in the scientific understanding of genetics, molecular biology, and organ functioning have inspired great hope that we would soon have fundamental understanding of the various disease processes and specific treatments to cure them. This expectation has so far been mostly unfulfilled. There is an enormous, and mostly unbridged, gap between the basic medical sciences and clinical practice. The more we learn about the body, the more we learn how much we don't know and how complicated and heterogeneous is the pathogenesis of disease. And despite the hype, much of medical research turns out to be simply wrong because the methods used are inadequate; the biases and conflicts of interest profound; and the data over or mis-interpreted1. The appropriate diagnostic thresholds and criteria for defining and diagnosing most diseases remain controversial. There is no bright line separating diabetes, hypertension, osteoporosis, or even many cancer-like cells from normal. As always, scientific medicine has been oversold and overbought – a recurring triumph of hope over experience. In the process, the Hippocratic emphasis on the doctor/patient relationship, natural healing, and doing no harm has been greatly undervalued. Most doctors treat lab tests, not patients; drugs are carelessly dispensed to those more harmed than helped by them; and medical mistakes are the third leading cause of death in the U.S.. All the inherent and pervasive limitations of scientific medicine are exaggerated in psychiatry, because its target organ of interest is the most complicated entity in the known universe. If we haven't yet gotten very far in dealing with cancer in the breast, the simplest organ in the body, how can we expect simple answers to the riddle of psychiatric disorders, arising from remarkably heterogeneous malfunctions in its most complex? I have known and admired A. Jablensky for almost 30 years and fully endorse his masterful summary of the current state of psychiatric diagnosis2. I find nothing to disagree with in his general analysis of the relationship between clinical utility and validity. Our current systems of psychiatric diagnosis are all crude, heterogeneous approximations that will seem silly and invalid as we slowly and painstakingly acquire deeper knowledge. There will probably not be any low hanging fruit when it comes to finding genetic explanations, characteristic imaging findings, or new treatments. Most studies won't replicate and there will be many seemingly promising, but very blind alleys. All this said, we should also not underestimate the current necessity of psychiatric diagnosis and its clinical utility in treating patients. The DSM-III was a response to a serious crisis in confidence in the credibility of psychiatry. It introduced two major innovations that radically changed psychiatric diagnosis and temporarily restored confidence: operational criteria to increase reliability of psychiatric diagnosis and the multiaxial system to increase its breath. Everything since the DSM-III has been little more than a footnote, often causing more harm than good. Let's do a brief report card of the positive and negative effects of DSM on the major domains of its influence: Clinical. A reliable diagnostic system is essential to meaningful clinical communication. To the extent that DSM criteria sets improve reliability, they help clinicians to talk a common language and to relate research findings to clinical practice. But reliability does not inhere only to how the criteria are written; it also depends on how well they are used. Sad but true, many clinicians are not well schooled in the criteria sets and continue to speak idiosyncratic diagnostic tongues. Education. The good news is that DSM criteria are a useful training tool in psychiatric diagnosis, but this is overwhelmed by the bad news that a reductionistic focus on criteria has often replaced what used to be a much more rounded evaluation of the person who has the symptoms. I don't trust clinicians who don't know DSM criteria, but I equally don't trust clinicians who focus only on DSM criteria and are blind to the complexity of life and human nature. Research. The DSM system that seemed to offer such a promising research tool has failed to live up to expectations and no longer guides much of the latest psychiatric research. It turned out that the DSM mental disorders are too heterogeneous to allow for simple research answers. The Research Domain Criteria framework instituted in the U.S. by the National Institute of Mental Health is also now promising much, but the lesson of the past is that brain research is exciting and essential, but extraordinarily difficult and often irrelevant to clinical practice. Progress in understanding mental illness has been, and will continue to be, frustratingly slow whatever method is used3. Epidemiology. It was impossible to gather meaningful statistics on the rates of mental disorders before there was a reliable way of diagnosing them. Although helpful in epidemiology, the DSM criteria based system has been applied in a systematically biased way to overstate rates. At the inherently fuzzy boundary between normal and disorder, the only (if fallible) demarcation is the presence or absence of clinically significant distress or impairment. The large number of assessments necessary in epidemiological research preclude the use of expensive clinicians and therefore cannot evaluate for clinical significance. Mild symptoms thus get mislabeled as mental disorders, and reported prevalences are upper limits, not real rates4. Forensic. The DSM-III seemed to provide a common language that might reduce the babel of opposing expert psychiatric testimony in forensic proceedings. To some degree, it has improved testimony, but is still as often misused as used well. The pressures created by the adversarial legal system encourage tortured misinterpretations of the criteria sets that the insufficiently precise DSM language is unable to prevent. Egregious misuses of psychiatric diagnosis remain a major problem in courtroom proceedings5. I probably understand the weaknesses of DSM diagnosis as well as anyone, but still appreciate its value. Opponents of psychiatric diagnosis often have a more one-sided and single-minded purpose: to use its weaknesses to argue for the complete abolition of psychiatric diagnosis. The British Psychological Society's widely publicized report "Understanding Psychosis and Schizophrenia" is a prime example6. In its effort to show that psychiatric diagnosis is unnecessary and does more harm than good, the report misleadingly lumps together all the very different usages of "psychosis" and blurs the essential distinctions they offer, thus losing crucial prognostic and treatment precision. "Psychosis" is used in at least six different ways, that can be teased out after careful differential diagnosis. Each has quite different implications regarding severity, chronicity, clinical significance, causality, and treatment: a) "psychosis" misused to describe anyone who occasionally experiences hallucinations (this overlooks the fact that 10% of the general public reports having had an hallucination, and 20% have had a direct encounter with an angel or devil; "psychosis" should be reserved only for those who are unable to reality test the hallucination and who also have accompanying significant distress and impairment in interpersonal and vocational functioning); b) psychosis caused by intoxication or withdrawal from alcohol, a medication, or a street drug; c) psychosis due to a medical or neurological disease; d) brief psychosis (a transient mental disorder with excellent prognosis and no reason to expect long-term impairment); e) psychosis occurring (usually episodically) as part of bipolar or major depressive disorder; f) psychosis occurring as a primary, often debilitating and chronic feature in schizophrenia and delusional disorder. The "Understanding Psychosis and Schizophrenia" report makes broad statements about the role of medication and psychosocial interventions that are essentially meaningless, because most certainly there is no one size that fits all the diagnoses loosely covered by the vague term "psychosis". The more precise language of psychiatric diagnosis saves precious information that is absolutely necessary for responsible clinical care. However limited the explanatory power of our current diagnostic system, it is great folly to ignore its very great clinical utility. The excellent is sometimes the enemy of the good. Expecting too much from the diagnostic system leads critics to ignore its value and necessity. We should all feel grateful to A. Jablensky for his clear and scholarly delineation of the issues and resetting of expectations. Allen Frances Department of Psychiatry and Behavioral Sciences, Duke University, Durham, NC, USA