Diagnosing mental disorders in the community. A difference that matters?
Brugha and his colleagues in this issue raise important questions about the validity of standardized diagnostic interviews of mental disorders, such as the Composite International Diagnostic Interview (CIDI) (WHO, 1990). Although their concerns refer predominantly to the use of such instruments in epidemiological research, the authors' conclusions also have significant implications for diagnostic assessments in clinical practice and research. We agree with Brugha et al. that the inflexible approach to questioning used in standardized interviews can lead to an increased risk of invalidity with regard to some diagnoses. We also agree that the use of more semi-structured clinical questions has the potential to address this problem. However, we disagree with Brugha et al. in several other respects.
First, we disagree with the authors' initial exclusive emphasis on diagnosis with regard to need assessment and consequences for the allocation of service resources. It is becoming increasingly clear that knowledge about diagnosis does not, in itself, whether assessed by clinical or non-clinical diagnostic interviews, provide sufficient information we need for policy purposes and the determination of societal costs, or to judge clinical management guidelines and treatment needs (Regier et al. 1998). Additional, preferably dimensional, data on associated disabilities and distress as well as a focused need evaluation for those psychosocial, psychological and drug interventions that characterize modern treatment strategies are also important. It also has become evident that a great many people in the general population carry more than one diagnosis. This ‘co-morbidity’ complicates further such simple equation of diagnosis prevalence with need assessment and policy decisions. Secondly, we disagree with the conclusion of Brugha et al. that the use of a semi-structured clinical interview, like the most current version of the Structured Clinical Assessment for Neuropsychiatry (SCAN), whether in the hands of clinical or non-clinical interviewers, is most closely approximating the ‘clinical gold standard’ and is the most feasible way to correct the problem of disagreement between semi-structured clinical diagnostic interviews and standardized diagnostic interviews. We believe that the practical reliability and validity problems associated with using such a clinical interviewing approach especially in large-scale community surveys as well as in cross-national research more than cancel out any theoretical advantage this approach might have in clarifying meaning. Thirdly, we disagree with the suggestion of Brugha et al. that the problem of validity is inherent in standardized non-clinician interviews. Indeed, as detailed below, there is no evidence that across all diagnoses clinical semi-structured interviews reveal more promising psychometric properties than standardized interviews. Also methodological research shows quite clearly that a substantial number of potential validity problems in standardized interviews can be overcome.
c1 Address for correspondence: Professor Hans-Ulrich Wittchen, Clinical Psychology and Epidemiology, Max Planck Institut für Psychiatrie, Kraepelinstrasse 10, 80804 Munich, Germany.