Long Life but High Suicide Rates in Sardinia’s Blue Zone: Evidence That Major Depression Alone May Not Explain the Paradox

Background: The Sardinian Blue Zone is internationally recognized for exceptional longevity, particularly among men. The provinces encompassing this area also report elevated suicide mortality among older men. This paradox raises the question of whether older men recruited within the longevity area show increased depressive screening positivity or whether additional interacting mechanisms may contribute to suicide vulnerability. Objective: To examine whether the reported excess suicide mortality among older men in the provinces encompassing the Sardinian Blue Zone is accompanied by higher depressive screening positivity or PHQ-9 Item 9 scores in older men recruited within the longevity area, and to explore the distribution of subthreshold depressive symptoms. Methods: We conducted an exploratory secondary analysis of a population-based survey including Sardinian residents aged ≥60 years. Depressive symptoms were assessed using the Patient Health Questionnaire-9 (PHQ-9). The Blue Zone group was recruited from six municipalities within the longevity area in Nuoro and Ogliastra. Comparisons were stratified by sex and used two-sided Fisher exact tests and analysis of variance. Results: No statistically significant increase in screening positivity for probable depression or PHQ-9 Item 9 scores was observed in Blue Zone residents. Older men showed a higher prevalence of clinically relevant symptoms below the screening threshold for probable major depression (PHQ-9 5–9: 4/19 vs. 4/171; OR = 11.13; Fisher p = 0.00395). Among women, this symptom range was less frequent in the Blue Zone (5/34 vs. 77/208; Fisher p = 0.01077). Conclusions: The observed symptom distributions motivate examination of mechanisms extending beyond the prevalence of major depression alone. The male excess in subthreshold depressive symptoms, interpreted alongside independent evidence on activation, supports investigation of mood and rhythm dysregulation and culturally shaped responses to stress. The sociobiological framework generates testable hypotheses for longitudinal psychiatric and anthropological research.