Risk and risk factors for disability pension among patients with treatment resistant depression- a matched cohort study.

BACKGROUND: Treatment resistant depression (TRD) is common among patients with depression, and is associated with clinical and functional disability. However, the risk and risk factors for being granted disability pension (DP) among patients with TRD have not been investigated. METHODS: All antidepressant initiators in Sweden with a diagnosis of depression in specialized care were identified in nationwide registers 2006-2013 and followed regarding treatment trials. TRD was defined as the start of a third sequential trial. Patients with TRD who were not on DP (N = 3204) were matched by age, sex, history of depression, calendar year, and time for treatment start with 3204 comparators with depression and ongoing antidepressant treatment. A proportional Cox Regression was performed with DP as outcome, adjusted for various sociodemographic and clinical covariates. RESULTS: Compared to the comparison cohort, TRD was associated with a doubled risk for all-cause DP (aHR 2.07; 95%CI 1.83-2.35), DP due to depression (2.28; 1.82-2.85) and to any mental disorder (2.24; 1.95-2.57) but not due to somatic diagnoses (1.25; 0.84-1.86). Among significant risk factors for DP in TRD were female sex, being > 29 years of age, unemployment and a diagnosis of comorbid personality disorder (ICD-10 codes F60.0-9). CONCLUSION: TRD is associated with an elevated risk for DP compared to other patients with depression, with large potential costs for the affected patients and for society. Clinical and therapeutic implications for patients with TRD who are granted DP should be further investigated. LIMITATION: No clinical data, e.g. type of depression or reason for treatment switch, was available for this study.