Mental Health
Revisiting the Diagnostic Algorithm: Implications for Depression Prevalence Daniel Hagen* Debbie Huang Huang Huang Huang California State University, Long Beach
The Patient Health Questionnaire (PHQ)-9 is among the most utilized screeners for major depressive episode (MDE). Despite being devised for screening, many prevalence studies use it, taking a summed score approach (cut-point≥10), which may overestimate prevalence. We employed a data-driven approach to revisit use of the less sensitive but more specific diagnostic algorithm scoring approach – which mirrors Diagnostic and Statistical Manual and Mental Disorders (DSM)-5 criteria for MDE and requires endorsement of at least 5 of 9 PHQ-9 symptoms at least more than half the days in the past 2 weeks, one of which must be depressed mood or anhedonia – in prevalence studies when gold standard diagnostic instruments are not feasible. To first quantify current use of screening instruments in prevalence studies, we conducted a scoping review of studies reporting depression prevalence and indexed in MEDLINE in 2024-25. Second, we analyzed data from the 2021-23 National Health and Nutrition Examination Survey (NHANES) to describe differences in weighted prevalence and sociodemographic, clinical and functioning indicators between adults (18+) who screened positive for depression using both the summed score and diagnostic algorithm approach vs. summed score approach only. Out of 298 studies using screening instruments to measure depression prevalence, 110 (37%) utilized the PHQ-9 with the summed score approach. Using NHANES data, the diagnostic algorithm scoring approach yielded a lower prevalence estimate (5% vs. 12% using summed score). Screening positive with the diagnostic algorithm was highly associated with greater functional impairment and symptom severity, but not with any sociodemographic characteristics. In studies measuring depression prevalence, the diagnostic algorithm may yield more realistic estimates than the summed score approach and identify those with more severe symptoms and greater functional impairment, serving as a better indicator of population need.