Early life exposure to cigarette smoke and depressive symptoms among women in midlife.

Introduction: Active cigarette smoking has consistently been associated with depression, but little is known about the association between other cigarette smoke exposures, particularly in early life, and depression. We investigated whether exposures to maternal smoking during pregnancy (MSP) and childhood secondhand smoke (SHS) are associated with depressive symptoms in midlife.
Methods: Pregnant mothers were enrolled and were provided data on maternal smoking and other parental characteristics. Female offspring were followed through age 7 years and again in midlife (age range = 38-44 years), when they provided data on smoking history, SHS across the life course, and current depressive symptoms using the Center for Epidemiological Studies Depression Scale (CES-D).
Results: Participants exposed to MSP had a higher risk for depression (risk ratio [RR] = 1.83, 95% confidence interval [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 for depression in midlife, with the association 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 they provide some support for the direction of smoke exposure influence on depression.
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