A systematic review and meta-analysis of the association between depression and insulin resistance

Abstract

Objective: Depression is associated with the onset of type 2 diabetes. A systematic review and meta-analysis of observational studies, controlled trials, and unpublished data was conducted to examine the association between depression and insulin resistance (IR).

Research design and methods: Medline, EMBASE, and PsycINFO were searched for studies published up to September 2011. Two independent reviewers assessed the eligibility of each report based on predefined inclusion criteria (study design and measure of depression and IR, excluding prevalent cases of diabetes). Individual effect sizes were standardized, and a meta-analysis was performed to calculate a pooled effect size using random effects. Subgroup analyses and meta-regression were conducted to explore any potential source of heterogeneity between studies.

Results: Of 967 abstracts reviewed, 21 studies met the inclusion criteria of which 18 studies had appropriate data for the meta-analysis (n = 25,847). The pooled effect size (95% CI) was 0.19 (0.11-0.27) with marked heterogeneity (I(2) = 82.2%) using the random-effects model. Heterogeneity between studies was not explained by age or sex, but could be partly explained by the methods of depression and IR assessments.

Conclusions: A small but significant cross-sectional association was observed between depression and IR, despite heterogeneity between studies. The pathophysiology mechanisms and direction of this association need further study using a purposively designed prospective or intervention study in samples at high risk for diabetes.

Figure 1

Flowchart of systematic review. *Further information in regards to excluded studies can be found in Supplementary Table 1.

Figure 2

Forest plots showing the effect size of the association between depression and insulin resistance. Estimates are at the center of the boxes and drawn in proportion to the SEs. Lines indicate 95% CIs. Diamond shows the pooled effect size at its center and 95% CI at its horizontal points. IGT, impaired glucose tolerance; NGT, normal glucose tolerance.

Figure 3

Forest plots of the unadjusted and adjusted association between depression and insulin resistance for studies with confounders included. Confounders adjusted for A: age, ethnicity, waist circumference, education, physical activity, antidepressants, medications for nervous conditions, site; B: age, sex, ethnicity, BMI; C: weight, BMI, waist-to-hip ratio; D: weight, BMI, waist-to-hip ratio; E: age, sex, BMI, comorbidity, education, physical activity, smoking, alcohol, geographical location, residential region; F: age, education, physical activity, smoking, alcohol, antidepressants, fish consumption; G: age, education, physical activity, smoking, alcohol, antidepressants, oral contraceptives, fish consumption, polycystic ovary disease; H: age, ethnicity, waist circumference, smoking, systolic blood pressure, triglyceride; I: age, ethnicity, waist circumference, smoking, systolic blood pressure, triglyceride; J: sex, BMI, education, physical inactivity, smoking, alcohol; K: sex, BMI, education, physical inactivity, smoking, alcohol; L: BMI, comorbidity, socioeconomic status, physical inactivity, smoking, alcohol, C-reactive protein, cholesterol level; M: BMI, comorbidity, socioeconomic status, physical inactivity, smoking, alcohol, C-reactive protein, cholesterol level; and N: waist circumference, education, physical inactivity, alcohol, smoking. IGT, impaired glucose tolerance; NGT, normal glucose tolerance.