Washington, March 2 (IANS) Existing anti-depressant treatments require three to four weeks to become effective, but a new drug seems to produce a rapid improvement in mood, say researchers.

Scopolamine temporarily blocks the muscarinic cholinergic receptor, thought to be overactive in people suffering from depression.

Wayne Drevets and Maura Furey of the National Institute of Health (NIH) recruited outpatients with major depressive disorder who were randomly assigned to receive a placebo and then scopolamine treatment o vice versa, in a double-blinded design so that neither the researchers nor the patients knew which treatment they were receiving.

'Scopolamine was found to reduce symptoms of depression within three days of the first administration. In fact, participants reported that they experienced relief from their symptoms by the morning after the first administration of drug,' explained Furey.

'Moreover, one-half of participants experienced full symptom remission by the end of the treatment period,' added Furey.

'Finally, participants remained well during a subsequent placebo period, indicating that the anti-depressant effects persist for at least two weeks in the absence of further treatment,' he said.

John Krystal, editor of Biological Psychiatry, which published these findings, commented that these findings 'have the potential to raise expectations for new anti-depressant treatments'.