UCLA

Background: Studies yield conflicting results for the relationship of educational attainment to depressive distress. In addition, there is competing evidence for the sex variations in this relationship.

Objectives: The aim of this study was to examine 1) the patterns of depressive distress across varying levels of education, and 2) whether there are sex differences in the effect of educational attainment on depressive symptoms.

Methods: This is a cross-sectional study using the most recent data available from the U.S. National Health and Nutrition Examination Survey (NHANES) 2015 – 2016. 4912 U.S. adults aged 20 years and older whose depressive distress was assessed with the Patient Health Questionnaire (PHQ-9) depression screener were analyzed. Adjusted multivariate logistic regressions and trend analyses were performed to examine the patterns of depressive symptoms across varying educational levels. Product terms were incorporated to detect whether there is departure from odds-ratio multiplicativity of effects. Additionally, relative excess risk due to interaction (RERI) was also evaluated for discerning the existence of deviation from additivity for the purpose of testing the effect measure modification (EMM) by sex.

Results: The weighted prevalence of depressive distress was 7.5%. An inverse association between educational attainment and depressive symptoms was detected and remained statistically significant after adjusting for potential confounders. In addition, trend analyses suggested a statistically significant linear trend in this association (P for trend = 0.0079). Compared to the highly educated, individuals who did not complete a high school degree had a much higher odds of displaying depressive distress (OR = 2.32, 95% CIs 1.59 - 3.38, P < 0.0001). However, no statistically significant departure from either odds-ratio multiplicativity or additivity of effects was observed, although RERI suggested a positive additive interaction between education and sex.

Conclusions: This study identified a linearly negative relationship between educational levels and depression. A higher level of educational attainment is associated with lower odds of showing depressive symptoms, independent of other risk factors. Furthermore, the effect of educational attainment on depressive distress was found to be homogeneous between males and females. This result reflects a major transition in certain social determinants in the context of the contemporary society in the U.S and further studies are needed to better understand this phenomenon.