Selective serotonin reuptake inhibitors (SSRIs) are a popular form of antidepressant medication that is widely used as a first-choice treatment for depression. SSRIs are as effective as other antidepressants, but often have fewer side effects. Many SSRIS are also less dangerous if accidentally taken at overdose levels. 

SSRIs are available by prescription in pill form. Scientists do not know precisely how they work, although they appear to leave more serotonin available in the body, thereby boosting mood. There are several different types of SSRIs available to treat depression, including extended-release or controlled-release formulations that are delivered to the body in a single dose over the course of a day or week.

SSRIs may also be used to treat disorders such as social phobia, obsessive-compulsive disorder, post-traumatic stress disorder and borderline personality disorder. Because the various SSRIs are all structurally distinct, a patient who does not respond to one SSRI may still gain relief from another SSRI.

Combining SSRIs with monoamine oxidase inhibitors (MAOIs) and other medications and supplements (e.g., St. John's wort) can lead to serotonin syndrome, a potentially fatal buildup of serotonin in the brain. Symptoms of SSRI overdose are generally less severe than those of other antidepressants, and may include unsteadiness, confusion, dizziness and diarrhea.

The safety of antidepressant use in pregnancy is not completely understood. Therefore, women who are pregnant, thinking of becoming pregnant or breastfeeding should consult their physician before using SSRIs. Because elderly patients may be more likely to experience side effects associated with SSRIs, lower dosage levels are often prescribed to this population.

The SSRI fluoxetine is the only antidepressant that has been approved for use in children. However, close monitoring of children taking this drug is recommended as it is associated with an increased risk of suicidal thoughts and behavior. The U.S. Food and Drug Administration (FDA) has required a “black box warning” on antidepressants, including SSRIs, because of their possible association with increased suicidal tendencies. It is extremely difficult to determine which individuals may be adversely affected by SSRIs. For this reason, children and adolescents using SSRIs must be closely monitored for worsening of depression or unusual changes in behavior.