Researchers found the effectiveness of a range of common sleeping tablets were of "questionable clinical importance".
The study questioned hypnotic pills, commonly known as 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 Prof 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.
"We know from other studies that around a fifth of people experience side-effects from sleeping tablets and one in 100 older people will have a fall, fracture or road traffic accident after using them.
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"Psychological treatments for insomnia can work as effectively as sleeping tablets in the short-term and better in the long-term, so we should pay more attention to increasing access to these treatments for patients who might benefit," he said.
Doctors said millions of prescriptions for Z-drugs every year as a short-term treatment for insomnia.
Some questioned whether the benefits of Z-drugs justify their side-effects, such as memory loss, fatigue or impaired balance.
Researchers used data submitted by pharmaceutical companies to the US Food and Drug Administration (FDA) for approval of new products.
The information was contained in 13 clinical trials, with more than 4,300 participants, that also had 65 "comparisons".
Findings indicated that "once the placebo effect is discounted, the drug effect is of questionable clinical importance".
The study was published in the British Medical Journal.