And you thought sleeping pills help you to doze off?

LONDON: Half of the benefits of taking sleeping pills may lie in the mind, coming from the placebo effect, a new major study has found.

Researchers found the effectiveness of a range of common sleeping tablets were of "questionable clinical importance". The study questioned hypnotic pills, Z-drugs, after re-analysing more than a dozen clinical trials.

Researchers from the University of Lincoln, Harvard Medical School and University of Connecticut, found drugs such as Sonata and Ambien worked once the placebo effect was taken into account, The Telegraph reported.

"Our analysis showed that Z-drugs did reduce the length of time taken for subjects to fall asleep," said Niroshan Siriwardena. "But around half of the effect of the drug was a placebo response. There was not enough evidence from the trials to show other benefits that might be important to people with sleep problems, such as sleep quality or daytime functioning ," Siriwardena said.

Findings showed "once the placebo effect is discounted, the drug effect is of questionable clinical importance".