We in psychiatry have always said it took 3-4 weeks for an antidepressant to show a clinical effect. Those who showed improvement in the first 2 weeks were thought to be having a placebo effect. In the past 2 years, there have studies that have shown that patients can have a “real” response to antidpressants as early as 1 week after starting the medication.
When Lexapro became available in 2002, pharmaceutical reps said it was supposed to show effect in the first week. At that time, that was the first antidepressant that made that claim. I find the literature still unclear about what is an expected response time. This is probably because there are other factors such as lack of support, ongoing stressors, variability in how drugs are metabolized that affect response time.
Also, another source of confusion may be in how we define “working”. A clinical response is not the same as a full recovery, so a person may experience some lifting of their depressed mood in the first week, but still have considerable irritability, insomnia, anxiety, etc. for several more weeks. Bottom line, I think the current literature supports early responses in the first week as being real and possible, but we still need to give the medications 4-6 weeks at a therapeutic dose to show a full response.
Let me know what you think