SSRIs are the first-line treatment for depression. They work by selectively inhibiting the reuptake of serotonin, increasing levels in the brain. Compared to older antidepressants, SSRIs have fewer side effects and are safer due to their selectivity for serotonin over other neurotransmitters. Common side effects include sleep problems, headache, nausea, and sexual dysfunction. Risks include discontinuation syndrome upon abrupt withdrawal and serotonin syndrome if taken with other serotonergic drugs. SSRIs are effective for several other disorders involving serotonin imbalance like anxiety disorders.