early l ife exposure to Cigarette s moke and Depressive s ymptoms a mong Women in Midlife

r esults: Participants exposed to MSP had higher risk of depression (risk ratio [RR] = 1.83, 95% CI = 1.08, 3.09) than those without MSP exposure. Relative to those with no MSP and no childhood SHS exposures, participants with MSP and childhood SHS had more than twice the risk of depressive symptoms (RR = 2.40, 95% CI = 1.07, 5.41). Further adjustment for adult factors, particularly current smoking, substantially reduced these associations (e.g., MSP vs. no MSP exposure: RR = 1.36 (95% CI = 0.75, 2.45). Conclusions: Early life exposure to cigarette smoke is associated with increased risk of depression in midlife, with the relation largely mediated by active smoking. These findings support a role for early life cigarette exposures in shaping smoking and depression risks in later life, and provide some support for the direction of smoke exposure influence on depression.