LONDON -- A study during which patients suffering from depression were given dummy pills is being taken as conclusive proof of the powerful "mind over body" effect of believing a drug will work, DPA reported.

Depressed patients tricked into thinking they are being treated undergo healing brain changes similar to those produced by Prozac, scientists have found.

And patients given a dummy pill containing no active ingredients experienced brain changes remarkably like those induced by Prozac, the world's most popular antidepressant.

In the first study of its kind, scientists at the University of Texas, San Antonio, U.S. compared brain scans of depressed patients either given Prozac or a placebo pill.

Seventeen depressed, hospitalized men took part in the study. Neither the patients nor the researchers knew who received the placebo until after the experiment.

Both groups of patients shared a pattern of increased activity in the cortex -- the "thinking" part of the brain -- and decreased activity in the limbic regions which govern emotion.

The researchers pointed out that such a response was necessary for a therapeutic benefit.

Of the 15 patients who completed the six-week study, eight showed improvement in their symptoms, half of whom had received the placebo.

However, there were important differences between the way the two sets of patients responded. Those who took Prozac experienced additional beneficial changes in lower areas of the brain -- the brainstem and hippocampus -- not seen in the placebo group.