Time trends in depression prevalence among Swedish 85-year-olds: repeated cross-sectional population-based studies in 1986, 2008, and 2015

Background Octogenarians of today are better educated, and physically and cognitively healthier, than earlier born cohorts. Less is known about time trends in mental health in this age group. We aimed to study time trends in the prevalence of depression and psychotropic drug use among Swedish 85-year-olds. Methods We derived data from interviews with 85-year-olds in 1986-1987 (N = 348), 2008-2010 (N = 433) and 2015-17 (N = 321). Depression diagnoses were made according to the Diagnostic and Statistical Manual of Mental Disorders. Symptom burden was assessed with the Montgomery-angstrom sberg Depression Rating Scale (MADRS). Information on psychotropic drug use, sociodemographic, and health-related factors were collected during the interviews. Results The prevalence of major depression was lower in 2015-2017 (4.7%, p < 0.001) and 2008-2010 (6.9%, p = 0.010) compared to 1986-1987 (12.4%). The prevalence of minor depression was lower in 2015-2017 (8.1%) compared to 2008-2010 (16.2%, p = 0.001) and 1986-1987 (17.8%, p < 0.001). Mean MADRS score decreased from 8.0 in 1986-1987 to 6.5 in 2008-2010, and 5.1 in 2015-2017 (p < 0.001). The reduced prevalence of depression was not explained by changes in sociodemographic and health-related risk factors for depression. While psychoactive drug use was observed in a third of the participants in each cohort, drug type changed over time (increased use of antidepressants and decreased use of anxiolytics and antipsychotics). Conclusions The prevalence of depression in octogenarians has declined during the past decades. The decline was not explained by changes in known risk factors for depression. The present study cannot answer whether changed prescription patterns of psychoactive drugs have contributed to the decline.