We test whether the heightened mortality after the death of a spouse represents correlation or causation by examining the heterogeneity in the bereavement effect based on the spouse's cause of death. Some causes of death are correlated with socioeconomic characteristics while others are not. Equality in the bereavement effect across these two types of death would signal a causal relationship while no bereavement effect for uncorrelated causes of death would indicate an omitted variables bias. Results indicate that the observed effect for women is subject to an omitted variables bias but the estimates for men indicate a causal relationship.