In two clinical trials of 120 abdominal surgery and 80 postoperative orthopedic patients, the experimenters intervened with a probiotic complex (containing Bifidobacterium and Lactobacillus) and L. rhamnosus GG for 4 weeks, respectively, from 7 days preoperatively to 14 days postoperatively, and the results of the trial indicated that the probiotic intervention resulted in a reduction in postoperative pain scores by 30%–50%, as well as a significant reduction in pro-inflammatory factors (IL-6,TNF-α) levels (↓38%–41%) and reduced opioid dependence (↓35%) (106, 108). This evidence concerns the gene IL6 and substance dependence.