Health, Wartime Stress, and Unit Cohesion: Evidence from Union Army Veterans We Both Gratefully Acknowledge the Support of Nih Grants R01 Ag19637 and R01 Ag027960. Dora Costa Also Gratefully Acknowledges the Support of Nih Grant P01 Ag10120. We Thank

JEL Classification: I12, Z13 We find that veterans of the Union Army who faced greater wartime stress (as measured by higher battlefield mortality rates) experienced higher mortality rates at older ages, but that men who were from more cohesive companies were statistically significantly less likely to be affected by wartime stress. Our results hold for overall mortality, mortality from ischemic heart disease and stroke, and new diagnoses of arteriosclerosis. Our findings represent one of the first long-run health follow-ups of the interaction between stress and social networks in a human population in which both stress and social networks are arguably exogenous. Dora L. Costa UCLA Department of Economics 9272 Bunche Hall Los Angeles, CA 90095-1477 and NBER [email protected] Matthew E. Kahn UCLA Institute of the Environment La Kretz Hall, Suite 300 Los Angeles, CA 90095-1496 and NBER [email protected]