Efficacy and Safety of Sertraline Combined With Lactobacillus Crispatus in Adolescents With Depression : A Multicenter Randomized Controlled Trial

The goal of this clinical trial is to evaluate the efficacy and safety of sertraline combined with Lactobacillus crispatus in adolescents aged 12-18 years with major depressive disorder. The main question it aims to answer is: Whether sertraline combined with Lactobacillus crispatus is superior to sertraline combined with placebo in reducing depressive symptoms and improving emotional symptoms in adolescents with depression. If there is a comparison group: Researchers will compare sertraline combined with Lactobacillus crispatus with sertraline combined with placebo ( look-alike substance that contains no probiotics) to determine whether the addition of Lactobacillus crispatus provides greater therapeutic benefit in adolescents with depression. Participants will: 1. Receive sertraline combined with Lactobacillus crispatus or sertraline combined with placebo for 8 weeks; 2. Attend clinic visits every 4 weeks for clinical assessments and safety monitoring