Objective: Prior work indicates a robust relationship between coffee consumption and lower depression risk, yet no research has examined links with psychological well-being (e.g., happiness, optimism). This study tested whether coffee intake is prospectively associated with greater psychological well-being over time. Secondarily, associations in the reverse direction were also examined to determine whether initial levels of psychological well-being were related to subsequent coffee consumption.
Methods: Among women in the Nurses' Health Study, coffee consumption was examined in 1990 and 2002 in relation to sustained levels of happiness reported across multiple assessments from 1992-2000 (N = 44,449) and sustained levels of optimism assessed from 2004-2012 (N = 36,729). Associations were tested using generalized estimating equations with a Poisson distribution adjusted for various relevant covariates. Bidirectional relationships were evaluated in secondary analyses of baseline happiness (1992) and optimism (2004) with sustained moderate coffee consumption across multiple assessments through 2010.
Results: Compared to minimal coffee consumption levels (<1 cup/day), moderate consumption (1-3 cups/day) was unrelated to happiness, whereas heavy consumption (≥4 cups/day) was associated with a 3% lower likelihood of sustained happiness (relative risk, RR = 0.97, 95% CI = 0.95-0.99). Only moderate coffee consumption was weakly associated with a greater likelihood of sustained optimism (RR1-3cups/day = 1.03, 95% CI = 1.00-1.06). Secondary analyses showed high levels of optimism but not happiness levels were modestly associated with increased likelihood of sustained moderate coffee intake (RRoptimism = 1.06, 95% CI = 1.02-1.10; RRhappiness = 1.01, 95% CI = 0.99-1.04).
Conclusions: Associations between psychological well-being and coffee consumption over up to two decades were largely null or weak. Although coffee consumption may protect individuals against depression over time, it may have limited impact on facets of psychological well-being.