Objectives: Individual clinical interviews are typically viewed as the "gold standard" when diagnosing major depressive disorder (MDD) and when examining the validity of self-rated questionnaires. However, this approach may be problematic with older people, who are known to underreport depressive symptomatology. This study examined the effect of including an informant interview on prevalence estimations of MDD in an aged-care sample.
Design: The results of an individual clinical interview for MDD were compared with those obtained when an informant interview was incorporated into the assessment. Results from each diagnostic approach were compared with scores on a self-rated depression instrument.
Setting: Low-level aged-care residential facilities in Melbourne (equivalent to "residential homes," "homes for the elderly," or "assisted living facilities" in other countries).
Participants: One hundred and sixty-eight aged-care residents (mean age: 84.68 years; SD: 6.16 years) with normal cognitive functioning.
Measurements: Individual clinical interviews were conducted using the Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition Axis I Disorders. This interview was modified for use with staff informants. Self-reported depression was measured using the Geriatric Depression Scale-15 (GDS-15).
Results: The estimated point prevalence of MDD rose from 16% to 22% by including an informant clinical interview in the diagnostic procedure. Overall, 27% of depressed residents failed to disclose symptoms in the clinical interview. The concordance of the GDS-15 with a diagnosis of MDD was substantially lower when an informant source was included in the diagnostic procedure.
Conclusion: Individual interviews and self-report questionnaires may be insufficient to detect depression among older adults. This study supports the use of an informant interview as an adjunct when diagnosing MDD among cognitively intact aged-care residents.