Does drug and alcohol use undermine concordance between doctors' assessments of major depression and patients' scores on a screening tool for depression among gay men attending general practice?

General practitioners (GPs) identify that depression can be difficult to diagnose in populations with high rates of alcohol and other drug (AOD) use. This is a particular concern with gay men who are a population known to engage in high rates of AOD use and who are vulnerable to depression. This paper uses data from 563 gay men and their GPs to describe concordance between assessments of major depression and, in particular, whether AOD use undermines concordance. Data were collected as part of a larger study of male patients and GPs at high HIV-caseload general practices in Australia. Concordance was measured by comparing patients' scores on the Patient Health Questionnaire-9 screening tool, which is based on the Diagnostic and Statistical Manual of Mental Disorders IV criteria, and GPs' ratings of the likelihood of depression for each participant. We observed high concordance between GPs' assessments of major depression and patients' scores on the PHQ-9 (79% agreement), although our analysis also suggested that concordance was better when it related to cases in which there was no depression. The high concordance observed in our study did not appear to be undermined by gay male patients' AOD use, with the exception of frequent use of crystal methamphetamine. Here, men who reported frequent use of methamphetamine were significantly less likely to have concordant assessments (adjusted odds ratio 0.3, 95% CI 0.1-0.8). Overall, GPs appear to identify depression among many of their gay male patients. While GPs should be aware of the potential complications presented by frequent crystal methamphetamine use, other AOD use may have less impact on the diagnosis of depression.