How should the effectiveness of an SSRI be evaluated?

The effectiveness of a selective serotonin reuptake inhibitor (SSRI) should be evaluated after a minimum of four weeks of treatment because these medications typically take time to build up in the system and exert their full therapeutic effects. SSRIs work by increasing the availability of serotonin in the brain, which is a process that requires consistent dosing over several weeks to achieve significant mood improvements.

In clinical settings, it is generally recognized that most patients do not experience the full benefits of an SSRI until they have been on the medication for at least four to six weeks. Evaluating their effectiveness too early, such as after a couple of days or even a week, may lead to premature conclusions about the treatment's efficacy. Additionally, the presence of side effects does not necessarily correlate with the medication's effectiveness; while some patients may experience side effects shortly after starting therapy, these do not imply that the medication is working for their depressive symptoms.

Therefore, waiting a minimum of four weeks allows for a proper and more reliable assessment of the medication’s effect and the patient’s response to the treatment.