Functional impairment can have different meanings.

Bedirhan Ustun and the World Health Organization (WHO) group have done the most sophisticated research on the assessment of disability as an integral part of psychiatric classification. As they note, the concept of disability adjusted life years (DALYs) changed the view of psychiatric disorders. Mental illness as compared to serious medical illnesses appeared high on the list of DALYs because mental disorders begin early in life and do not result in early mortality, so that the number of years lived with the disorder is often quite long, resulting in many more DALYs. The high rate of DALYs for psychiatric disorders, demonstrated across the world, has had a profound effect on thinking about psychiatric illness and has made the assessment of functional impairment and disability important in any psychiatric classification system. In this paper, the WHO group proposes to unify the measurement and collection of data on disability between the DSM and the WHO’s International Classification of Functioning, Disability and Health (ICF). I agree with the importance of unifying these systems and also with developing operational criteria for making the assessments. The authors state that the concept of functioning is a neutral one, encompassing all decrements to body functions, activities, involvement in life situations which are known at the body level as impairment, at the personal level as activity limitation and at society level as participation restrictions. The authors point out that there is similarity between ICD and DSM in the operationalization of diagnosis. The notable exception is that ICD does not require clinical significance to make a diagnosis but requires the ICF operational criteria of disability as a separate domain. The DSM-IV Global Assessment of Functioning (GAF), the ICF checklist and the WHO Disability Assessment Scheduled (DAS) all include measures of social functioning which are comparable, such as interpersonal interactions, getting along with people, and occupational or school functioning. These areas can easily be translated across domains and also have relevance cross-culturally. I would question using items like learning and applying knowledge or communication, which are absent from the GAF, as part of functioning and disability criteria. These items are related to education, income and IQ. Their inclusion in an assessment of disability may confound functioning with education. Bedirhan Ustun suggests that the ICF domains need to be operationalized and I would strongly agree, as similar domains may still have different interpretations. Several years ago, we were asked to compare three functioning scales in a primary care study 1. All three of these scales (the Medical Outcome Study, 36-item Short Form Health Survey, SF-36; the Social Adjustment Self-Report, SAS-SR; and the Social Adaptation Self Evaluation Scale, SDSS) measure work functioning. All scales, when applied to patients in a primary care study, were able to differentiate between psychiatrically ill and well people. However, the correlations between the scales were modest even in the areas covering similar domains. A comparison of the questions included in the scales showed how the approaches to work assessment differed. The SAS-SR assesses the actual number of days lost, the effective performance and interpersonal relationships on the job, whereas the SDSS emphasizes interest and motivation, and the SF-36 asks about problems with work. While each of these scales covered the area of assessment of work, their approaches to work functioning were quite different. We recommended that investigators selecting a functional status assessment instrument carefully review the content of each scale and, if a broad range assessment is very critical, use more than one scale. In conclusion, I would agree fully with Bedirhan Ustun and the WHO’s recommendation that functional impairment be assessed separately from symptoms. It will be useful to have this assessment similar across the different diagnostic systems. Considerable attention needs to be paid to the comparability of the questions in each of the domains.