Disentangle diagnosis and disability
Authors: ANTHONY F. LEHMAN
Journal: World Psychiatry (2009)

Üstün and Kennedy argue that the DSM system should be made more compatible with the ICD system, specifically that the “functional impairment” criterion for DSM diagnoses should be removed. They make a compelling argument and raise at least two important issues. First, should “functional impairment” and “disability” be included among diagnostic criteria for mental disorders as they are in the DSM, but not in the ICD? Second, how can we make the DSM and ICD compatible on this issue so that there is international consistency for the classification of mental disorders as there is for other medical disorders? Their essay focuses on some of the technical aspects of defining and measuring “functional impairment”, “disability” and “severity”, and the option of aligning the Global Assessment of Functioning (GAF) from the DSM with the International Classification of Functioning, Disability and Health (ICF) associated with the ICD. Why have we felt the need to confound diagnosis and functional impairment in the DSM in the first place? This reflects our struggles, at least on one side of the Atlantic, with the state of differentiating mental illness from normal variations in human mental processes and behaviors. When are hallucinations, sad mood or obsessive thoughts pathologic? Presumably this has occurred in the DSM because of anxiety that without the requirement of “clinical significance” the door could be opened to substantial unnecessary mental health care utilization for subsyndromal disorders that do not reach clinical significance. Of course, it is essential to ensure that valuable health care resources are utilized in an efficient and essential manner for conditions that indeed affect the health of individuals. However, the DSM solution may be worse that the problem. While there is undoubtedly unnecessary mental health care utilization, we know that by far the greater problem is underutilization. Over half of persons who meet criteria for a mental disorder receive no care 1. The inclusion of “clinical significance”, and more specifically “functional impairment”, in the diagnosis creates an illusion of greater diagnostic certainty than is needed in order to “eliminate” those who have sub-clinical syndromes from accessing care. Most such persons are de facto eliminated by personal choice or by lack of access to services. This approach has major problems. It severely restricts our capacity to intervene in a preventative manner with those who are experiencing early signs of, or are at risk for, impending mental illness. As Üstün and Kennedy point out, this approach is contrary to that in other areas of medicine. The current DSM system is analogous to not intervening to treat hyperlipidemia, borderline high blood pressure, or border-line hyperglycemia until the sequelae of these risk factors become apparent as overt, symptomatic, or disabling cardiovascular and renal disease. The issue of risk factors raises a second point. The ultimate goal of health care is to reduce avoidable morbidity and mortality. There is an inherent circularity to inclusion of morbidity (i.e., functional impairment) as a diagnostic criterion since it means that some morbidity already has to occur to make the diagnosis. Hence we are left with the option of reducing existing morbidity rather than preventing it in the first place. This is akin to treating hyperlipidemia only after the onset of angina or a heart attack. It blocks the way to prevention and treatment for prodromal states. It also impedes research into risk factors for development of disorders as well as disability. In order to move to a diagnostic system that enables us to study as well as intervene with risk factors and subsyndromal conditions, we need to make the changes that Üstün and Kennedy propose.