Sertraline is a selective serotonin reuptake inhibitor (SSRI) primarily used to treat depression, anxiety disorders, obsessive-compulsive disorder, and post-traumatic stress disorder. Its active ingredient, sertraline hydrochloride, works by increasing serotonin levels in the brain, which helps improve mood and emotional stability. The medication is available in tablet form and typically taken once daily. Common side effects may include nausea, insomnia, and sexual dysfunction.