Predictor effect plots summarizing the role of intervention and surgery type on predicted values of the BDI (A), HRSD (B), and Insomnia (C). BDI—beck depression inventory, HRSD—Hamilton psychiatric rating scale for depression, RYGB—Roux-en-Y gastric bypass, SG—sleeve gastrectomy. P—p value obtained from a general mixed-effects model for the three-way interaction, i.e., type of surgery (RYGB versus SG) by intervention (Placebo versus Probiotic) by time (Before versus After); BDI—Beck Depression Inventory, HRSD—Hamilton Psychiatric Rating Scale for Depression, RYGB—Roux-en-Y Gastric Bypass, SG—Sleeve Gastrectomy.