Life course central depressive symptoms among the moderately depressed population: From adolescence to old age

The features of depression vary across different life stages due to different social and developmental factors. Utilizing two nationally representative samples (total N = 51,970), moderately depressed residents were identified using the PHQ-9 scale (cut-off ≥10), and 10,181 residents (5167 males; age_{range =}11.63-94.48 years) were finally included. Participants were categorized into 13 age groups and five life stages. A Gaussian graphical model examined the depressive network structure, global network strength, and central symptoms, with network comparison tests performed to identify differences. The prevalence of moderate depression varied between 16.57 % and 25.12 % across age groups. Significant differences in network structure were found in 28 of 78 pair comparisons (p.s < 0.045). Global network strength exhibited a distinctive trajectory: increasing from under 18 to 30-34 years, decreasing at 60-64 years, increasing again at 65-69 years, and finally decreasing at 75+ years. Similar to previous research, sadness emerged as the central symptom in almost all stages, and central symptoms varied across life stages (p.s < 0.048). Unique central symptoms were identified in different developmental stages: sadness and fatigue in adolescence/emerging adulthood, failure and sadness in young adulthood, suicidality and sadness in middle adulthood, and disturbed appetite in older adulthood. These findings underscore the importance of considering a life course perspective when developing interventions for depression, as central symptoms and network metrics of depression vary significantly across different life stages.