Selective serotonin reuptake inhibitors, or SSRIs, are a class of medications commonly used to treat depression and anxiety disorders. They 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 can lead to improved mood and emotional balance. SSRIs are often prescribed because they tend to have fewer side effects compared to older antidepressants. Common examples include fluoxetine, sertraline, and escitalopram. While they can be effective, it may take several weeks to notice their full benefits, and they should be taken under the guidance of a healthcare professional.