Onset of action of antidepressants

Recent guidance from the National Institute for Health and Clinical Excellence (NICE) says that antidepressant drugs should be offered routinely to all patients with depression of at least moderate severity and recommends a selective serotonin reuptake inhibitor as first line treatment.1 The NICE guidance goes on to state that “Patients started on antidepressants should be informed about the delay in onset of effect.” This reflects conventional wisdom, but is it time to revisit this idea?

Speed of onset of the actions of antidepressants is clinically important for several reasons. Delayed onset means that depression, its associated disability, and for some patients the potential risk of suicide continue. Early onset of effects may improve future compliance and thus outcomes.

When tricyclic antidepressants were first introduced in the 1950s delays in antidepressant effects were not reported. Indeed, researchers on early tricyclic antidepressants …