A Selective Serotonin Reuptake Inhibitor, or SSRI, is a type of medication commonly used to treat depression and anxiety disorders. SSRIs work by increasing the levels of serotonin, a neurotransmitter in the brain that helps regulate mood, by preventing its reabsorption into nerve cells. This action enhances mood and emotional stability. SSRIs are often prescribed because they tend to have fewer side effects compared to older antidepressants. Common examples of SSRIs include fluoxetine, sertraline, and escitalopram. While effective for many, they may not work for everyone, and it is important to consult a healthcare professional for proper diagnosis and treatment.