Mental health scales and psychiatric diagnoses: responses to GHQ-12, K-10 and CIDI across the lifespan.

BACKGROUND: Surveys based on complex interviews like CIDI report very low rates of affective disorder in older people, perhaps because the lengthy, convoluted questions present a special challenge to aged respondents. By contrast, mental health scales like the GHQ-12 and K-10 show much less change in score with age. Before concluding that scales present a fairer picture of aged mental health, it is important to check if scores are inflated by items that might reflect normal involutional changes in cognition, energy and social role.
METHODS: Secondary analysis of an Australian national survey of 10,641 adults.
RESULTS: GHQ-12 and K-10 scores declined with age to a relatively minor degree. When scores were bisected, the proportion of respondents scoring above the cutpoints fell with age but to a lesser degree than with ICD-10 diagnoses. Scores on GHQ-12 and K-10 items relating to cognition, energy and social role rose with age but, on factor analysis, these items loaded similarly in a two-factor model.
CONCLUSION: No evidence emerged of age-related bias in either GHQ-12 or K-10. Items concerning cognition, energy and social role were associated with affect in older people, just as they were in younger ones. It seems unlikely therefore that the different trajectories over the lifespan of CIDI diagnoses and scores on GHQ-12 and K-10 are due to limitations within the scales. The possibility that CIDI minimizes affective disorder in older age-groups cannot be discounted. LIMITATIONS: Residents of aged care facilities and those with low cognitive scores were excluded. Copyright 2009 Elsevier B.V. All rights reserved.