What the evidence says about SSRIs and SNRIs for Anxiety

SSRIs and SNRIs are the most studied medications for anxiety, and meta-analyses consistently find they outperform placebo across the major anxiety disorders. A 2015 meta-analysis by Bandelow and colleagues, pooling treatment trials across the anxiety disorders, found small to moderate effect sizes for both classes against placebo. A 2019 network meta-analysis in the Lancet by Slee and colleagues compared drug treatments for generalized anxiety disorder and found that several SSRIs and SNRIs outperformed placebo, with the differences between agents within the class being small.

Response builds over weeks, not days. A meaningful effect typically appears over four to six weeks, and a full response can take eight to twelve weeks. This slow onset matters clinically, because a patient who expects a fast result may stop early and conclude the medication failed before it had a fair trial.

There's no strong evidence that any one SSRI is meaningfully better than another for anxiety overall. Because efficacy is broadly similar within the class, the choice between agents is usually driven by the side-effect profile, possible drug interactions, prior response, and cost.

If you need a plain-language explainer to share with patients or families, PsychiatryRx has a psychiatrist-reviewed animation that lets you see how SSRIs work at the synapse, with a toggle to compare it with SNRIs.