In this paper, we estimate the causal effect of social security income on mental health. We focus on widowhood, a life event associated with large and persistent mental health declines, and exploit a reform of the Dutch survivor benefits system that introduced cohort-based restrictions in benefit eligibility. Using administrative data, we find that reduced access to survivor benefits increases antidepressant use by 9%, accounting for 35% of the overall rise in antidepressant use following spousal death. A mechanism analysis shows that survivor benefits stabilize mental health by smoothing living standards, highlighting the potential welfare gains from well-targeted income support policies.