Background: Marital status is important to the epidemiology of Psychiatric disorders. In particular, the high prevalence of major depression in individuals with separated, divorced, or widowed status has been well documented. However the literature is divided as to whether marital disruption results in major depression and/or vise versa. We examined whether major depression influences changes of marital status, and, conversely, whether marital status influences the incidence of this disorder Methods: We employed data from, the longitudinal Canadian National Population Health Survey (1994-2004), and proportional hazards models with time-varying covariates. Results: Major depression bad no effect on the proportion of individuals who changed from single to common-law, single to married, or common-law to married status. In. contrast, exposure to depression doubled the proportion of transitions from common-law or married to separated or divorced status (HR = 2.0; 95% CI 1.4-2.9 P < 0.001). Conversely an increased proportion of nondepressed individuals with separated or divorced status subsequently experienced major depression (hazard ratio, HR = 1.3; 95% CI 1.0-1.5 P = 0.04). Conclusion: The high prevalence of major depression in, separated or divorced individuals is due to both an increased risk of marital disruption in those with major depression, and also to the higher risk of this disorder in those with divorced or separated marital status. Thus a clinically significant interplay exists between major depression and marital status. Clinicians should be aware of the deleterious impact of major depression on marital relationships. Proactive management of marital problems in clinical settings may help minimize the psycho-social "scar" that is sometimes associated with this disorder. Depression and Anxiety 26:1172-1177, 2009. (C) 2009 Wiley-Liss, Inc.