SSRIs are a class of antidepressant drugs that work by inhibiting the reuptake of serotonin in the brain. They are commonly used to treat depression but also anxiety, OCD, and other disorders. While SSRIs take weeks to have an effect due to their mechanism of action beyond just increasing serotonin levels, they have fewer side effects than older antidepressants. Common side effects include nausea, sexual dysfunction, insomnia, and headaches. Drug interactions can occur and serotonin syndrome is a potential risk. SSRIs are generally preferred over older antidepressants due to their safety profile.