Disability and diagnosis: should role impairment be eliminated from DSM/ICD diagnostic criteria?

Ustun and Kennedy propose that “no functioning or disability should appear as part of the threshold of the diagnosis” of any disorder. They note that disentangling disability/impairment from disorder would bring the DSM into greater conformity with the ICD. However, the real issue is conceptual: can disability criteria – understood, as in DSM clinical significance criteria, as impairment of social role functioning (not to be confused with psychological dysfunction appearing as symptoms) – be entirely disentangled from diagnostic criteria at this point in psychiatry’s history? In a related vein, Robert Spitzer and I 1, 4 have argued that DSM “clinical significance” criteria using impairment generally are not very useful for distinguishing disorder from non-disordered problems in living, because non-disordered problems often entail role impairment. Recent studies tend to support the redundancy of broad DSM-like impairment criteria in both clinical and epidemiologic contexts 5, 7. Despite ICD’s explicit goal to avoid using family, occupational and other social role functioning as diagnostic criteria, because they vary cross-culturally, social disability enters into many ICD criteria sets. For example, conduct disorder requires “major violations of age-appropriate social expectations”; reading disorder must “significantly interfere with academic achievement or activities of daily living that require reading skills”; and neurasthenia involves “decrease in occupational performance or coping efficiency in daily tasks”. Ustun and Kennedy fail to explain why ICD criteria still contain so many references to disability. They offer no systematic argument that disability and disorder can be fully disentangled. The absurdity of using disability itself as a sufficient indicator of disorder is readily apparent; how can pathological disability then be distinguished from normal inability? 8. Consider the disability from sleep (one-third of life spent paralyzed and hallucinating), pregnancy, fatigue after exertion, and other normal human limitations; normal variation in traits like intelligence, shyness, and height that disadvantage some; and differences in knowledge, skill, and talent that yield variations in ability to perform social roles. It is not disability but how it is caused that makes it pathological. Given this absurdity, the logic of DSM regarding potential use of impairment for diagnosis is more troubling than one might suspect and goes well beyond specific “clinical significance” criteria. The DSM’s introductory section on the impairment criterion explains: “This criterion helps establish the threshold for the diagnosis of a disorder in those situations in which the symptomatic presentation by itself (particularly in its milder forms) is not inherently pathological and may be encountered in individuals for whom a diagnosis of ‘mental disorder’ would be inappropriate”. Thus, impairment is allowed to change the status of a condition from non-disorder to disorder. Moreover, the DSM explains that one situation in which a condition can be diagnosed under a “not otherwise specified” category is when “the presentation con-forms to a symptom pattern that has not been included in the DSM-IV classification but that causes clinically significant distress or impairment”. Such symptom patterns include subthreshold conditions with fewer than the usually required symptoms. In sum, the DSM implicitly allows the diagnosis of problematic conditions with few symptoms as disorders based simply on role impairment, contrary to the DSM’s own definition of disorder requiring that impairment be caused by internal dysfunction. A corrective of the sort suggested by Ustun and Kennedy is plainly needed. But the fact that disability does not imply disorder does not mean that disability has no role whatever in diagnosis. According to both the DSM definition of mental disorder and my “harmful dysfunction analysis” (HDA) of the concept of disorder 8, 9, a disorder is an internal dysfunction (meaning a failure of a biologically designed function) that causes harm (as socially evaluated). Thus, the HDA proposes that diagnosis has two dimensions: dysfunction and harm. Consequently, disability can legitimately appear in diagnostic considerations for two reasons. First, it can constitute harm. Generally, the direct symptoms of dysfunction will be harmful enough, but there are instances of disorder in which role impairment is the only type of harm and must be cited to establish that there is a disorder. This points to a basic fallacy: Ustun and Kennedy appear to assume that a disorder is equivalent to the underlying dysfunction. However, even an internal dysfunction that is biologically pathological is not a medical disorder unless it causes harm. For example, benign angiomas are genuine dysfunctions, yet not medical disorders because there is no harm. All individuals have many such biological flaws that are not medical disorders due to lack of harm. Thus, role impairment sometimes is needed to determine whether a dysfunction is harmful and thus to distinguish disorder from non-disorder. Second, sometimes there is no independent way to establish that there is a dysfunction versus a non-disordered problem of living other than by social impairment. One such situation is when a role capacity is itself biologically shaped, so failure of the social function implies biological dysfunction. For example, when social phobia occurs when interacting with family members, such basic functions as parenting and sexual interaction are compromised. This is simultaneously role impairment and biological dysfunction. Another such situation is when role failure, though itself not a biological dysfunction, is the only way to infer that there is an underlying dysfunction. For example, reading is an invention, and its failure is a failure of a social function nonexistent in preliterate societies. Nor is inability to read – illiteracy – considered a disorder. But often it is only from the failure to learn to read despite opportunity that we infer that the inability is due to underlying dysfunction. Because that unknown dysfunction has no other harmful effects, we must cite the social impairment of failure to learn to read as a key to diagnosis. In sum, there are reasons to support Ustun and Kennedy’s general thrust to attempt to the degree possible to separate role impairment from diagnostic criteria. But Ustun and Kennedy fail to consider adequately the multifaceted conceptual relations between diagnosis and disability, which are illuminated, I have maintained, by the harmful dysfunction analysis’s two-dimensional account of disorder in terms of dysfunction and harm. I conclude that Ustun and Kennedy’s proposal to totally disengage impairment from diagnosis is unrealistic at this stage in psychiatry’s development as a science. In terms of validity of criteria, a category-by-category conceptual analysis would be preferable to their blanket approach.