Cause-specific mortality in treatment-resistant major depression: Population-based cohort study.

ABSTRACT

BACKGROUND: Limited evidence-base on long-term prognosis of treatment-resistant major depression (TRD) is a barrier to clinical decision-making. Therefore, the purpose of this study was to establish cause-specific mortality in TRD compared to non-TRD major depression. METHOD: We identified all individuals with a diagnosis of major depression (MDD) who were treated with an antidepressant aged 15 to 65 years during 2004-2016 in Finland. Persons with over two treatment trials were defined to have TRD. Data were analysed with Cox proportional hazard models. RESULTS: 176,942 individuals with MDD (63 % women, median age at index diagnosis 40 years), of whom 11 % (n = 19,305) fulfilled the TRD criteria, were followed-up for 1,525,646 person-years (median 8.9 years). There were 959 deaths (6.1 deaths/1000 person-years) in TRD and 7662 deaths (5.6/1000 person-years) in non-TRD. All-cause mortality was 17 % higher (adjusted hazard ratio (aHR), 1.17; 95 % confidence interval (CI), 1.09-1.25) in TRD compared to non-TRD, when sex and age at index antidepressant prescription were controlled for. In TRD, increased mortality was observed for suicides (aHR, 1.90; 95%CI, 1.64-2.20) and for accidental poisonings (aHR, 1.81; 95%CI, 1.48-2.22), but not for natural causes (aHR, 0.98; 95%CI, 0.90-1.07). A higher proportion of accidental drug overdoses was observed in TRD than in non-TRD (62 % vs 42 %, respectively). LIMITATIONS: Definition of TRD lacks consensus. We used routine data to define TRD. CONCLUSIONS: The markedly increased mortality due to suicides and accidental overdoses suggests that persons with TRD may experience higher intensity symptoms and more severe suicidal ideation than persons with non-TRD major depression.