Similar results were observed for depression severity as a continuous variable at follow-up: PLS regression with baseline propionate, butyrate, and CRP concentrations and baseline depression severity as the independent variables explained 18.2 % of the variance in follow-up depression severity (two-factor solution), with baseline depression severity, propionate, and butyrate, but not CRP, exceeding the VIP threshold of 0.8 (details in supplement), indicating that a combination of these variables may be useful in explaining future depression severity [Fig. 1D]. This evidence concerns the gene CRP and major depressive disorder.