Suicide risk among low-income household members suffering from depression: A population-based retrospective cohort study.

Depression and suicide risk among low-income individuals not only share common epidemiological patterns but may also be driven by underlying bidirectional mechanisms. On one hand, the social causation hypothesis suggests that financial stress, food insecurity, and unstable housing significantly increase the risk of developing depression. On the other hand, the social drift hypothesis indicates that depression often leads to impaired occupational functioning, job loss, and financial decline, creating a feedback loop where poverty exacerbates depression, and depression, in turn, perpetuates poverty. In this context, we hypothesized that depressed patients from low-income backgrounds would have a higher propensity for suicide, as the risk may arise both because of poverty and as a consequence of untreated or chronic depression. This is also consistent with behavioral economic evidence showing that clinical depression alters time and risk preferences and consumption-related dysfunction. We acknowledge the feedback loop where depression exacerbates poverty and vice versa, thus further increasing suicide risk among low-income individuals. To evaluate this, we utilized the Taiwan National Health Insurance Research Database to examine whether depression in low-income individuals is significantly associated with an elevated risk of suicide. The present cohort study obtained data from the National Health Insurance Research Database. From a total of 1,936,512 patients included in the Longitudinal Health Insurance Dataset between 2000 and 2015, 771 low-income participants who had suffered from depression and 3084 controls matched for gender and age were selected. Cox proportional hazard regression analysis was employed to explore the hazard ratio, and 95% confidence intervals (CIs) for low income being associated with the risk of developing psychiatric disorders during the 16-year follow-up period were calculated. Of the 771 low-income, depressed patients and 3084 control participants, 60 (8514.66 per 105 person-years) and 138 (36,269.29 per 105 person-years) developed suicidal thoughts, respectively. The Cox regression model revealed an adjusted hazard ratio (AHR) of 1.771 (95% CI = 1.289-2.432, P < .001) after adjusting for all the covariates. Depression among low-income individuals was associated with Charlson Comorbidity Index (AHR = 1.097; 95% CI = 1.004-1.186, P = 1.186). Factors of suicide methods by using Cox regression included other gases and vapors (AHR = 8.149; 95% CI = 5.926-11.196, P < .001), and cutting and piercing (AHR = 2.789; 95% CI = 2.021-3.864, P < .001). Depression and low income are independent risk factors for suicide. Depressed low-income patients are at higher risk of developing suicidal thoughts compared with depressed non-low-income patients. Among suicide methods, gases and vapors have the highest risk. Therefore, clinicians should pay attention to the income level of depressed patients.