2026 ECNP Congress

PS03-3103

Lifetime suicidal ideation is associated with depressive symptom level and variability in a Korean longitudinal cohort

JunCheol Shin — S. Min, M. Hong, M.H. Mun, H. Lee, S.J. Rhee, Y.M. Ahn · Seoul National University Hospital, Department of Neuropsychiatry, Seoul, Korea- Rep

2026 ECNP Congress

Background

In psychiatry, longitudinal monitoring is important for judging treatment response and early detection of relapse, and self-report questionnaires are repeatedly administered to quantify symptoms. PHQ-9 in particular is a brief depression symptom questionnaire and one of the most commonly used instruments in psychiatry for both cross-sectional screening and longitudinal monitoring [1]. However, the optimal frequency for administering such questionnaires to accurately assess symptom status remains unclear. This study aimed to investigate factors associated with PHQ-9 trajectories, summarized by PHQ-9 mean and within-person standard deviation.

Methods

In the LIFELOG Korean longitudinal cohort, 278 participants contributed at least five weekly observations during a 26-week self-report follow-up. Per-subject PHQ-9 mean and within-person standard deviation (SD) were computed. Study participants were stratified by recruitment method, psychiatric diagnosis, and C-SSRS lifetime ideation positivity. Lifetime suicidal ideation was coded positive when any C-SSRS lifetime ideation item 1-5 was endorsed [2]. Because hospital-recruited participants were nearly all ideation-positive, the C-SSRS contrast was tested within the community stratum. Analyses used Mann-Whitney U with rank-biserial r, Kruskal-Wallis H with epsilon-squared, Holm correction, adjusted rank-OLS, and a random-intercept mixed-effects model on raw weekly PHQ-9.

Results

At baseline, the community group (n=182) showed lower distress and higher quality-of-life scores than the hospital group (n=96; |r|=0.43-0.63). C-SSRS lifetime ideation was positive in 93 of 96 hospital-recruited participants (97%), supporting restriction of the ideation contrast to the community group. Within the community group, lifetime ideation positivity was associated with higher PHQ-9 mean (4.50 vs 2.43, r=+0.41 [+0.24, +0.56], Holm p=2e-4) and higher PHQ-9 within-person SD (2.08 vs 1.36, r=+0.39 [+0.22, +0.55], Holm p=3e-4). After adjustment for age, sex, and diagnosis, lifetime suicidal ideation remained associated with PHQ-9 mean (rank-OLS coef=+18.50, p=0.016) and PHQ-9 SD (coef=+20.20, p=0.013); PSQI (p=0.044), MHC (p=0.029), and WHO-QoL psychological domain (p=0.031) also remained associated, whereas GAD-7, UCLA Loneliness, satisfaction, and other WHO-QoL domains did not. A random-intercept mixed-effects model on raw weekly PHQ-9 confirmed higher PHQ-9 level among ideation-positive participants (beta for ideation=+2.97, p<1e-6, n=2,934 observations / 163 subjects). Participants with diagnosed bipolar disorder or major depressive disorder had higher PHQ-9 mean and SD than those without psychiatric diagnosis (epsilon-squared=0.10-0.40), while alcohol use disorder did not differ from the no-diagnosis group on PHQ-9 mean or SD.

Conclusions

In this Korean community-clinical longitudinal cohort, lifetime suicidal ideation was statistically associated with higher PHQ-9 mean and greater 26-week within-person PHQ-9 variability. The presence of lifetime suicidal ideation may reflect a history of stressful events and subsequent depression, which, following stress sensitization theory [3], could lower the threshold for future depressive episodes. Our findings that higher mood-related diagnostic burden was associated with higher PHQ-9 mean and SD support this interpretation. The presence of lifetime suicidal ideation may also indicate exposure to stress-prone environments or serve as a proxy for neuroticism, reflecting greater vulnerability to negative affect under stress. These findings suggest that lifetime suicidal ideation history may support routine assessment in longitudinal monitoring, as it may help identify individuals at risk for persistently elevated and more variable depressive symptom burden.

References

  1. Kroenke K, Spitzer RL, Williams JBW. The PHQ-9: validity of a brief depression severity measure. Journal of General Internal Medicine. 2001;16(9):606-613.
  2. Posner K, Brown GK, Stanley B, Brent DA, Yershova KV, Oquendo MA, Currier GW, Melvin GA, Greenhill L, Shen S, Mann JJ. The Columbia-Suicide Severity Rating Scale: initial validity and internal consistency findings from three multisite studies with adolescents and adults. American Journal of Psychiatry. 2011;168(12):1266-1277.
  3. Monroe SM, Harkness KL. Life stress, the kindling hypothesis, and the recurrence of depression: considerations from a life stress perspective. Psychological Review. 2005;112(2):417-445.