Depression and cause-specific mortality in an ethnically diverse cohort from the UK: 8-year prospective study

BACKGROUND: Depression is associated with increased mortality, however, little is known about its variation by ethnicity. METHODS: We conducted a cohort study of individuals with ICD-10 unipolar depression from secondary mental healthcare, from an ethnically diverse location in southeast London, followed for 8 years (2007-2014) linked to death certificates. Age- and sex- standardised mortality ratios (SMRs), with the population of England and Wales as a standard population were derived. Hazard ratios (HRs) for mortality were derived through multivariable regression procedures. RESULTS: Data from 20 320 individuals contributing 91 635 person-years at risk with 2366 deaths were used for analyses. SMR for all-cause mortality in depression was 2.55(95% CI 2.45-2.65), with similar trends by ethnicity. Within the cohort with unipolar depression, adjusted HR (aHRs) for all-cause mortality in ethnic minority groups relative to the White British group were 0.62(95% CI 0.53-0.74) (Black Caribbean), 0.53(95% CI 0.39-0.72) (Black African) and 0.69(95% CI 0.52-0.90) (South Asian). Male sex and alcohol/substance misuse were associated with an increased all-cause mortality risk aHR:1.94 (95% CI 1.68-2.24) and aHR:1.18 (95% CI 1.01-1.37) respectively, whereas comorbid anxiety was associated with a decreased risk aHR: 0.72(95% CI 0.58-0.89). Similar associations were noted for natural-cause mortality. Alcohol/substance misuse and male sex were associated with a near-doubling in unnatural-cause mortality risk, whereas Black Caribbean individuals with depression had a reduced unnatural-cause mortality risk, relative to White British people with depression. CONCLUSIONS: Although individuals with depression experience an increased mortality risk, marked heterogeneity exists by ethnicity. Research and practice should focus on addressing tractable causes underlying increased mortality in depression.