Longitudinal Analysis of Associations Between Dietary Patterns and Incident Suicidal Ideation

Background/Objectives: Diet is a key modifiable determinant of mental health; however, the prospective association between dietary patterns and new-onset suicidal ideation remains poorly elucidated. Methods: We enrolled 7480 participants from demolition resettlement communities in Jining, Zoucheng, and Weifang in Shandong Province, China, during 2021–2023. Data were used from two waves (baseline and 1-year follow-up) in this study. Dietary patterns were determined using principal component analysis based on food frequency questionnaire data. Incident suicidal ideation was assessed using the ninth item of the Patient Health Questionnaire-9. Multivariable logistic regression, stratified analysis, and sensitivity analysis were used to examine associations of different dietary patterns with the risk of incident suicidal ideation. Results: Among participants, 193 (2.58%) reported incident suicidal ideation. After full multivariable adjustment, the livestock–poultry–seafood dietary pattern was significantly inversely associated with incident suicidal ideation (Q3 vs. Q1; odds ratio = 0.67; 95% confidence interval: 0.45–0.97), whereas no significant association was identified when the pattern score was modelled continuously (OR = 0.92; 95% CI: 0.79–1.06; p = 0.239). Stratified analyses revealed stronger inverse associations among men, older adults, overweight individuals, and participants who did not use dietary supplements, but all interaction p-values exceeded 0.05, with no statistically confirmed subgroup disparities. After excluding participants with baseline depression, participants with baseline anxiety, and individuals with missing covariates in sensitivity analysis, the inverse association remained statistically stable. Conclusions: Our findings suggested a modest inverse association between higher adherence to the livestock–poultry–seafood dietary pattern and new-onset suicidal ideation in this observational cohort.