Background: It has been stated that it takes two to three weeks before a response to an antidepressant medication is apparent. Studies supporting this predated the use of selective serotonin reuptake inhibitors (SSRIs). Some trials have shown that the delay in response to SSRIs is similar to other antidepressants. However, other studies have shown that SSRIs have a statistically significant improvement within as little as one week when compared with placebo. The early response to SSRIs may reflect a true effect or may be a chance event. To evaluate this issue, Taylor and colleagues performed a systematic review and meta-analysis of randomized trials to determine if there is an early response to SSRIs in the treatment of depression.
The Study: The authors searched the literature for randomized, placebo-controlled trials of fluoxetine (Prozac), fluvoxamine (Luvox), citalopram (Celexa), escitalopram (Lexapro), sertraline (Zoloft), and paroxetine (Paxil). The studies assessed these antidepressant medications in the treatment of unipolar depression. The authors used multiple databases for the literature search, and reviewed reference lists from the articles selected and related systematic reviews. Data extracted were trial design, participant characteristics, and outcomes. When reported, data from depression rating scores or changes in scores over the first six weeks of treatment were also extracted. Trials were eliminated if the participants were limited to adults 65 years and older or to those with specific comorbidities.
Results: The authors identified 28 trials that met inclusion criteria; these included 3,618 participants who received SSRIs and 2,254 in placebo groups. The pooled data were analyzed to assess the treatment effect of SSRIs compared with placebo for weeks 1 through 6 of treatment.
Patients treated with SSRIs were found to have greater clinical improvement by the end of week 1 compared with those in the placebo group. This improvement continued over time, but the increment of benefit decreased week by week. In those studies using the Hamilton Depression Rating Scale, treatment that resulted in a 50 percent reduction in this score at week 1 was significantly more likely to occur with SSRIs than with placebo (relative risk = 1.64; 95% confidence interval, 1.2 to 2.25). Those studies using the Montgomery-Asberg Depression Rating Scale showed similar results.
Conclusion: The authors conclude that symptomatic improvement in depression occurs with the use of SSRIs by week 1 and continues during the first six weeks of treatment, but at a declining rate. An early response to this class of antidepressants may represent a true response and not a placebo effect.