Depression is a prevalent mental illness and a major cause of disability worldwide. An estimated 280 million people worldwide were affected by depression, contributing to over 47 million disability-adjusted life-years in 2019 (Vos et al., 2020). Numerous studies have proven that depression increases the risk of mortality (Cuijpers et al., 2014). It is also associated with premature death from other illnesses such as cardiovascular disease (CVD) or cancer (Walker et al., 2015; Zhang et al., 2023).

Modification of established risk factors is effective in the prevention of depression (de Pablo et al., 2021). Understanding the factors leading to the excess mortality risk is a prerequisite to an effective intervention. The excess mortality of depression might reflect the biological sequelae of depression itself as well as a high burden of health risk behaviors (HRBs). Co-occurrence of depression and HRBs is very common. For example, epidemiological data show that the smoking rate among the population with depression is about twice the rate among the general population in the United States (US) (Mathew et al., 2017). People with depression also experience a range of barriers, including depressive symptoms, higher body mass index, or physical co-morbidity to engaging in physical activity. These people are reported to have 50 % higher odds of being physically inactive than the general population (Schuch et al., 2017).

Data are emerging that HRBs are important risk factors for mortality among population with depression. However, the extent to which HRBs contribute to excess mortality of depression is not clear. In this study, we aimed to systematically examine the collective contribution of four major modifiable HRBs to the excess mortality in the population with depression. These HRBs included smoking, excessive alcohol use, physical inativity, and unhealthy diet (Noble et al., 2015). The data from the National Health and Nutrition Examination Survey (NHANES) provides a unique opportunity to fulfill our research goal.