The nose knows danger: Linking olfactory deficits to suicidal behaviors in emerging adulthood

Suicide prediction remains limited by the absence of objective biomarkers, particularly in adolescents with major depressive disorder (MDD), among whom suicide rates are rising. This study investigated olfactory function as a potential biomarker across groups with suicidal ideation (SI), suicide attempts (SA), and healthy controls (HC).

Olfactory performance was assessed using the standardized Sniffin' Sticks test (odor threshold, discrimination, identification, and total TDI scores) in 72 adolescents with MDD (42 with SI, and 30 with SA), and 43 matched HCs. Depression severity was controlled using Beck Depression Inventory-II (BDI-II) scores.

Adolescents with suicidal thoughts and behaviors (STB) showed significantly higher odor identification (OI) than HCs (12.72 ± 1.35 vs. 11.86 ± 1.51, t = -3.19, p < 0.01). After adjusting for covariates in the ANCOVA, group differences in odor identification remained significant (F = 9.32, p < 0.01). OI independently predicted STB (OR = 1.90, 95 % CI: 1.24-3.13, p < 0.01), with strong classification accuracy (AUC = 0.913). One-way ANOVA revealed no significant group effect on odor discrimination (OD) (F = 2.34, p = 0.10).

Enhanced odor identification differentiates suicidal adolescents from healthy peers and predicts suicide risk with high accuracy. Stronger odor discrimination may offer protection against transition to suicidal behavior. These findings suggest olfactory testing could aid early suicide risk assessment in depressed youth.