Why is water insecurity so distressing? Evidence from Iran that interpersonal conflict is key.

Chronic household water insecurity is consistently linked to distress and poor mental health, yet the social pathways remain under-tested. We examine multiple theorized socially situated mechanisms that may explain how household water insecurity translates into depressive symptoms, using population-representative 2024 survey-interview data (N = 685) from Sistan and Baluchestan, Iran. Household water insecurity (HWISE-12), depressive symptoms (PHQ-9), and five mechanisms-interpersonal conflict, distributive injustice, procedural injustice, institutional distrust, and water-labor burden-were measured with validated or locally developed scales. Structural equation modeling estimated direct and indirect effects, adjusting for gender, residence, age, education, income, and household size. Mean HWISE scores exceeded prior global benchmarks and mean PHQ-9 scores were higher than clinical cut-points for moderate depression, confirming both extreme insecurity and high levels of psychosocial distress. Findings suggest multiple nonmaterial mechanisms work simultaneously to link water insecurity to poor mental health. The model explained more variance in men's depression (R2 = .34) than women's (R2 = .14). Interpersonal conflict was the strongest and most consistent statistical mediator of PHQ-9 scores. Stronger effects for men (β = .47) than women (β = .22) are likely related to men's roles in local water governance. Perceived distributive injustice was associated with higher PHQ-9 scores across groups, while procedural injustice was significant only for men and in urban settings. Distrust of water-related institutions was significant only among women, while burdens of water labor were associated with PHQ-9 scores for both genders, particularly in rural settings. Household income did not account for these associations once social mechanisms were considered. We highlight the need for mixed-method research to refine theory and interventions that recognize the many ways water insecurity operates socially to shape distress and related mental health outcomes.