It is known that changes in family structure can be a predictor of depression [4, 12], but the relationship between various changes in household size and depression has not been reported in detail. Unlike previous research, this study measured various changes in family size and showed their effects on depressive symptoms more dynamically. A shift from a larger family to a smaller one was shown to predict a higher probability of having depression. Previous studies that mainly targeted the elderly and children have shown similar results to ours [7, 12, 13]. However, this study can be said to be more generalizable as it covered all Korean adults. Larger families tend to provide financial, emotional, and social support to their members. In Korea, women can then share their responsibilities with their children, which is a lost benefit when the household size shrinks. Most children move to single households when they pursue a university education or a job, which are among the usual causes for increased social pressures. However, their support from family members is reduced during this period. Additionally, the loss of a spouse or migration usually offsets memories and creates gaps in people’s lives that are most likely to result in depression.
This study established that those who move from smaller families to larger ones have lower rates of depression, which is consistent with Tattarini et al. [9] ’s finding that larger families displayed better health. This result is attributed to the care provided by the family, which is a shielding factor against social shocks [9]. Larger households are formed when people get married, have children, or join a shared household. These events provide opportunities for members to share stories and create new memories, acquire emotional and financial support, and widen their social bubble. The sharing of roles, meals, and costs is good for individuals’ mental health and reduces their chances of experiencing depression.
Staying in a household of the same size over time was not associated with depression, but the prevalence of depression was higher among those remained in a single-person household. This result is consistent with Shao et al. [8] ’s finding that university students living alone displayed higher levels of depression. This result shows that even when the entire population has high depression rates, those living in single households have a higher risk of depression. Turagabeci et al. [14] identified the lack of companionship as one of the major causes of poor health among those who live alone. They cited that such individuals usually have meals alone and that most of them eat outside of their homes and reach home later than those in other family structures. The number of people living in single-person households is on the rise, and our findings reinforce the need for intervention.
One of the important limitations of this study is that it measured the presence or absence of depression, not the onset of depression, which is an outcome variable. Therefore, the results of this study could not clearly indicate a causal relationship between changes in family size and the occurrence of depression. However, this study did not fail to reveal the relationship between these two factors because it sensitively measured changes in family size.
This report reemphasizes the impact of social mobility on health outcomes and highlights the issue of depression among a growing population group: single-person households. To establish a wider understanding of this topic, we encourage more extensive studies, especially focusing on mental health outcomes, which are associated with changes in family structure.