Six studies [32, 34, 37, 38, 40, 41] out of seven [13, 32, 34, 37, 38, 40, 41] found that increased circulating levels of proxy markers of gut dysbiosis (A1-AT, I-FABP, endotoxins, antibodies against endotoxins) were significantly associated with more severe symptoms of depression in MDD [34, 37, 38, 40, 41] and bipolar disorder [32, 40]. This evidence concerns the gene FABP2 and depressive symptom measurement.