Lifestyles' role in the relationship between socioeconomic deprivation and depression

To explore the specific role and underlying mechanisms of lifestyles in the socioeconomic inequalities in depression.

A total of 299,310 participants from the UK Biobank were included. Cases of depression were identified based on electronic health records. Socioeconomic status (SES) was assessed using the Townsend Deprivation Index. Smoking, alcohol consumption, physical activity, sleep duration, leisure activities, dietary score, and obesity were used to construct the overall lifestyle risk score. Cox proportional hazard regression models, mediation and moderation analysis and multiple sensitivity analyses were used.

During a median follow-up of 8.94 years, 13,344 participants (4.46 %) developed depression. Compared with the highest SES group, the lower-middle and the lowest SES group had a 13 % (HR = 1.13, 95%CI: 1.08-1.19) and 49 % (HR = 1.49, 95%CI: 1.42-1.57) increased risk of depression, respectively. Lifestyles included in this study could explained approximately one-third of the socioeconomic disparity in depression. A significant interaction between lifestyle categories and SES were found (P_interaction < 0.01). In the groups with the highest, upper-middle, lower-middle, and lowest SES, participants with the least healthy lifestyle had a 50 % (HR = 1.50, 95%CI: 1.37-1.65), 53 % (HR = 1.53, 95%CI: 1.40-1.68), 73 % (HR = 1.73, 95%CI: 1.59-1.88), and 74 % (HR = 1.74, 95%CI: 1.62-1.86) increased risk of depression, respectively, compared to those with the healthiest lifestyle in the same SES category.

The association between SES and depression was significantly mediated by lifestyles. Reducing socio-economic inequalities is equally important as promoting healthy lifestyles among the population. Particular attention should be paid to the impoverished.