The Influence of Educational Attainment on Depression and Risk of Type 2 Diabetes

Abstract

Objectives-We investigated the association between major depressive disorder and type 2 diabetes, whether that association is explained by health behaviors, and whether it is influenced by educational attainment.Methods-We used discrete-time Cox proportional hazards models to determine the risk of type 2 diabetes associated with depression in a 23-year population-based cohort study. Results-Major depressive disorder was associated with higher risk of type 2 diabetes (hazard ratio[HR]=1.62) after we controlled for age, gender, race, education, smoking status, alcohol use, social network size, and antidepressant use. This association was more pronounced after we controlled for body mass index, family history, and health behaviors (HR=2.04; 95% confidence interval=1.09, 3.81). In stratified analyses, the risk associated with major depressive disorder was elevated among those with 12 or fewer years of education compared with those with at least some education beyond high school.Conclusions-The risk of type 2 diabetes associated with major depressive disorder persists over the life course and is independent of the effects of health behaviors, body mass index, and family history. Education is an important moderator of this association.Numerous retrospective observational studies have reported higher prevalence of depression among diabetic populations than among controls. 1,2 In the first prospective analysis, Eaton et al. found approximately 2 times higher risk of type 2 diabetes among those with major depressive disorder (MDD) 13 years previously than among those without depression, 3 a finding that has been replicated with remarkable consistency. 4 It is unclear whether the elevated risk of type 2 diabetes associated with depression is mediated by poor health behaviors (e.g., smoking, physical inactivity), physiological changes, or both. Depression is associated with Requests for reprints should be sent to Briana Mezuk, Department of Epidemiology, University of Michigan, 3644 SPH Tower, 109 Observatory, Ann Arbor, MI 48109 (bmezuk@umich.edu). Contributors B. Mezuk was the project coordinator for the Baltimore Epidemiological Catchment Area Study and completed the analyses and led the writing of the article. W. W. Eaton is the principal investigator of the Baltimore Epidemiological Catchment Area Study and supervised all aspects of its implementation. S. H. Golden assisted with the analyses and drafting the article. Y. Ding assisted with the data setup and analyses. All authors helped to originate ideas, interpret findings, and review drafts of the article. Human Participant ProtectionThis study was approved by the Johns Hopkins School of Public Health institutional review board and all participants gave informed consent. NIH Public Access NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript lower socioeconomic status, 5 but it is unknown whether indicators such as educational attainment moderate the associated risk of type 2 diabetes. One previous study suggested that the risk of type 2...

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“…We also included a number of other variables so we could control for several known predictors of depression and anxiety. These included: years in education, as a longer period in education has been found to be related to 9 lower levels of depression in later life [35]; certain medications (antidepressants, anxiolytics, mood stabilisers/anti-epileptics, neuroleptics, sleeping tablets, betablockers and tetrabenazine, the latter of which can have side-effects of anxiety and depression [36]); past use of antidepressants and anxiolytics, and history of depression (no assessment of history of anxiety is included in REGISTRY); cigarette use (number per day) and alcohol use (units per day), as these have both been found to affect depression and anxiety [37][38][39]; largest CAG repeat length and the Total Motor Score from the UHDRS (a composite measure of different motor tasks, including oculomotor function, dysarthria, chorea, dystonia, gait and postural stability, with higher scores indicating more motor impairment).…”

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“…Many epidemiological, psychological and psychiatric studies aim to study causal environmental effects without being designed to do so. For example, studies have shown associations between 'exposures' such as education or life events and mental health outcomes (Bannink et al, 2013;Dalgard et al, 1995;Flouri & Kallis, 2011;Kinderman et al, 2013;Mezuk et al, 2008), and such associations often are interpreted as evidence of causal effects. However, as there are substantial genetic influences on both educational level and certain types of life events Kendler & Baker, 2007;Kendler et al, 1999;Tambs et al, 2012) the associations may be partly or entirely explained by genetic confounding.…”

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“…Examining the papers cited in the reviews and others published since then, we noted that the more clinically robust the instrument used to classify the depression was, the more likely the study was to find a significant association between T2D and a previous diagnosis of depression (58,92) or depressive symptoms (28,32,43,79). The studies defining depression on the basis of depressive symptoms collected within a general mental health scale were less likely to find a statistically significant elevated risk (8,46), although some did (13,25).…”

“…Two studies found an interaction with education (13,58), such that individuals with low education and depression were at greater risk for the development of T2D than both those with more education and depression and those with neither risk factor. Again, two studies also found gender differences, reporting an association of T2D with depression in males but not in females (25,92).…”

“…For example, the Alameda County Study found that childhood SES was a risk factor for adult T2D in women but not in men after adjusting for a wide array of eha ioral risk fa tors , a d the Nurses' Health "tud fou d a i reased risk of T D o l for o e hose father as lue or lo er hite ollar. Also rele a t as the fi di g, i t o U" studies, of a interaction between depression and low social status (13,58); the studies found an increased risk of developing T2D only in people with both depression and low social status after controlling for behavioral risk factors. The fact that SES has been shown to interact with depression and to differ in relevance by gender suggests that SES needs to be more carefully considered in the analysis and not be included merely as an adjustment variable.…”