SSRI

SSRI stands for selective serotonin reuptake inhibitor. It's a class of medications used to treat depression, anxiety disorders, OCD, PTSD, and several other conditions by adjusting how serotonin moves between nerve cells.

Definition from Shrinktionary, reviewed by Shariq Refai, MD, MBA, FAPA (last reviewed 2026-06-27). Shrinktionary is the network's language layer and carries the canonical short definition; this page adds the research-context detail below. Full definition on Shrinktionary →

SSRIs act on serotonin, a chemical messenger in the brain, by slowing its reabsorption. Common SSRIs include sertraline, escitalopram, fluoxetine, and paroxetine. Despite the name antidepressant, they're well studied and widely used for anxiety. They usually take four to six weeks to show a clear effect, and sometimes longer for a full response.

SSRIs are first-line drug treatment for generalized anxiety disorder, social anxiety disorder, and panic disorder in US and international guidelines. Meta-analyses find small to moderate effects compared with placebo. No single SSRI has been shown to be clearly better than the others for anxiety overall, so the choice often depends on side effects and prior response.

A person with generalized anxiety disorder starts a low dose of an SSRI. The dose is raised gradually, and the clinician reassesses after several weeks, because the medication needs time to work.

SSRIs carry an FDA boxed warning about a raised risk of suicidal thoughts in patients under 25, and close monitoring is standard early in treatment. They can cause side effects, including sexual side effects, which are a common reason people stop. Stopping suddenly can cause discontinuation syndrome, so they're lowered with a taper.