Selective Serotonin Reuptake Inhibitors, known as SSRIs, are prescribed drugs used to treat depression. Discovered in the 1970s, they are a breakthrough treatment because compared to older anti-depressants, they cause fewer side effects, are safer to use, and do not interact with most medications. Some studies have found that they are only effective for major (not mild) depression. SSRIs work by increasing serotonin, a natural substance found in the brain. They block the reabsorption or reuptake of serotonin in the brain by acting on chemical messengers called neurotransmitters. SSRIs only change the levels of serotonin and not other brain chemicals, which is why they are called “selective.” Besides depression, certain SSRIs are prescribed to treat panic disorders, bulimia, obsessive-compulsive disorders, generalized anxiety disorder, premenstrual dysphoric disorder, post-traumatic stress syndrome (PTSD), and social anxiety. Side effects of SSRIs can be nausea, dry mouth, headache, diarrhea, nervousness, agitation or restlessness, reduced sexual desire or difficulty reaching orgasm, inability to maintain an erection (erectile dysfunction), rashes, increased sweating, weight gain, drowsiness, and insomnia.