Abstract
Dispositional optimism is a potentially modifiable factor and has been associated with multiple physical health outcomes, but its relationship with depression, especially later in life, remains unclear. In the Nurses´ Health Study (n = 33,483), we examined associations between dispositional optimism and depression risk in women aged 57–85 (mean = 69.9, SD = 6.8), with 4,051 cases of incident depression and 10 years of follow-up (2004–2014). We defined depression as either having a physician/clinician-diagnosed depression, or regularly using antidepressants, or the presence of severe depressive symptoms using validated self-reported scales. Age- and multivariable-adjusted Cox proportional hazards models were used to estimate hazard ratios (HRs) with 95% confidence intervals (95% CIs) across optimism quartiles and for a 1-standard deviation (SD) increment of the optimism score. In sensitivity analyses we explored more restrictive definitions of depression, potential mediators, and moderators. In multivariable-adjusted models, women with greater optimism (top vs. bottom quartile) had a 27% (95%CI = 19–34%) lower risk of depression. Every 1-SD increase in the optimism score was associated with a 15% (95%CI = 12–18%) lower depression risk. When applying a more restrictive definition for clinical depression, the association was considerably attenuated (every 1-SD increase in the optimism score was associated with a 6% (95%CI = 2–10%-) lower depression risk. Stratified analyses by baseline depressive symptoms, age, race, and birth region revealed comparable estimates, while mediators (emotional support, social network size, healthy lifestyle), when combined, explained approximately 10% of the optimism-depression association. As social and behavioral factors only explained a small proportion of the association, future research should investigate other potential pathways, such as coping strategies, that may relate optimism to depression risk.
Highlights
One in five individuals experience at least one major depressive episode in their lifetime
Four prospective studies have assessed the association between dispositional optimism and incident depression [7,8,9,10]
We examined in a large prospective cohort of middleaged and older US women whether dispositional optimism predicted risk of incident depression in later life
Summary
One in five individuals experience at least one major depressive episode in their lifetime. Individuals with higher dispositional optimism—i.e., high expectations for positive outcomes in the future and low expectations for negative events [6]—experience significantly lower risk of depression and related outcomes [7,8,9,10], partially explained by better coping [11, 12], receiving more social support [13, 14] and a healthier lifestyle [15]. Despite a large body of literature on the association of dispositional optimism and depression-related outcomes, evidence from longitudinal studies with detailed confounder adjustment remains scarce. Among 464 elderly men (mean age 70.8 years), high vs low optimism predicted a lower cumulative incidence of depressive symptoms over 15 years of follow-up, after detailed control for confounding [10]. No study has examined this association among women of comparable age, who are generally more likely to experience depression [18, 19]
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