Combined lifestyle, childhood trauma and depressive symptoms in adults with subthreshold depression: a prospective cohort study

Abstract Aims Existing evidence on the association between combined lifestyle and depressive symptoms is limited to the general population and is lacking in individuals with subthreshold depression, a high-risk group for depressive disorders. Furthermore, it remains unclear whether an overall healthy lifestyle can mitigate the association between childhood trauma (CT) and depressive symptoms, even in the general population. We aimed to explore the associations of combined lifestyle, and its interaction with CT, with depressive symptoms and their subtypes (i.e. cognitive-affective and somatic symptoms) among adults with subthreshold depression. Methods This dynamic cohort was initiated in Shenzhen, China in 2019, including adults aged 18–65 years with the Patient Health Questionnaire-9 (PHQ-9) score of ≥ 5 but not diagnosed with depressive disorders at baseline. CT (present or absent) was assessed with the Childhood Trauma Questionnaire-Short Form. Combined lifestyle, including no current drinking, no current smoking, regular physical exercise, optimal sleep duration and no obesity, was categorized into 0–2, 3 and 4–5 healthy lifestyles. Depressive symptoms were assessed using the PHQ-9 during follow-up. This cohort was followed every 6 months, and as of March 2023, had been followed for 3.5 years. Findings This study included 2298 participants (mean [SD] age, 40.3 [11.1] years; 37.7% male). After fully adjusting for confounders, compared with 0–2 healthy lifestyles, 3 (β coefficient, −0.619 [95% CI, −0.943, −0.294]) and 4–5 (β coefficient, −0.986 [95% CI, −1.302, −0.671]) healthy lifestyles were associated with milder depressive symptoms during follow-up. There exists a significant synergistic interaction between a healthy lifestyle and the absence of CT. The CT-stratified analysis showed that compared with 0–2 healthy lifestyles, 3 healthy lifestyles were associated with milder depressive symptoms in participants with CT, but not in those without CT, and 4–5 healthy lifestyles were associated with milder depressive symptoms in both participants with and without CT, with a stronger association in those with CT. The lifestyle-stratified analysis showed that CT was associated with more severe depressive symptoms in participants with 0–2 healthy lifestyles, but not in those with 3 or 4–5 healthy lifestyles. Cognitive-affective and somatic symptoms showed similar results. Conclusions In this 3.5-year longitudinal study of adults with subthreshold depression, an overall healthy lifestyle was associated with subsequent milder depressive symptoms and their subtypes, with a stronger association in adults with CT than those without CT. Moreover, an overall healthy lifestyle mitigated the association of CT with depressive symptoms and their subtypes.