Overall, cigarette smoking, excessive alcohol consumption, marijuana use, elevated circulating TG, CRP, and IL-6 levels, decreased DHA and increased omega-6: omega-3 fatty acid ratios, BMI, AAM, shorter telomere lengths, intestinal flora, type 2 diabetes mellitus, and breast cancer were associated with increased risk of MDD. Here, IL6 is linked to type 2 diabetes mellitus.