The first thing to establish is the validity of this claim. So what is the latest evidence for it?

"How long to wait for an antidepressant to ‘work’

Current Psychiatry. 2007 June;6(6):62-65

Author(s): Ronald Pies...

Several recent studies demonstrate a real, drug-based response in many patients as early as the first week of treatment.

Prevailing wisdom says it takes 3 to 4 weeks for an antidepressant to show clinical effect. Historically, patients who improve in the first 2 weeks have been labeled “placebo responders.” Several recent studies, however, demonstrate a real, drug-based response in many patients as early as the first week of treatment, depending on the medication... In practical terms, these studies raise the question of how long you should wait for an antidepressant to “work.”"

Since antidepressants may not achieve their maximum benefit for 1-2 months or longer, it is not unusual for a trial of therapy to last 8-12 weeks at therapeutic doses. The antidepressants are successful in achieving remission in about 30-40% of patients with in a single trial of 8-12 weeks. If an inadequate response is obtained , therapy is often switched to other agents. Once an adequate response is achieved , continuation therapy is recommended for a minimum of 6-12 months to reduce the substantial risk of relapse.

Respected Sir these lines are taken as it from the text book of Basic and Clinical Pharmacology 12th edition 2012 by Bertram G. Katzung, MD, Ph.D from University of California,San Francisco

ISBN 978-0-07-176401-8

ISSN 0891-2033

Chapter number 30 Antidepressant Agents page number 521and above lines you will see on page number 532 as it with out a single word change .

Regards and thanks for asking validation

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"Regards and thanks for asking validation"

Any textbook is from 5 to 10 years out of date. I vaguely recall having seen evidence challenging this previous consensus, and a brief check (see my previous post) confirms this. You need to cite a recent journal paper or review to check the latest studies.

"it is widely held that antidepressants do not exert their effects for 2-4 weeks. This is a myth. All antidepressants show a pattern of response where the rate of improvement is highest during weeks 1-2 and lowest during weeks 4-6" This quotation is from the 10th edition of the Maudsley prescribing guidelines. They reference meta-analysis which debunk the myth. Anyway most teaching has so far been that there is a 2-4 weeks time lag before antidepressant effect but there have been several studies which contradict this previously widely held view.