Published in the online edition of the British Medical Journal, the study also found that doctors following this practice rarely admit that they are doing so to their patients.
Placebo treatments have been very controversial to date. While their critics claim that the practice is deceptive and violates patients' autonomy, their advocates argue that they offer effective treatment for many chronic conditions without necessarily deceiving patients.
Lead researcher Jon Tilburt and his colleagues from the National Institutes of Health, Harvard, and the University of Chicago examined the attitudes and behaviours to placebo treatments in a national sample of general internal medicine physicians and rheumatologists in the US.
The researchers sent a confidential survey to 1200 randomly selected practising general internal medicine physicians and rheumatologists.
They found that 57 per cent of the 679 physicians surveyed prescribed "placebo treatments" on a regular basis.
According to them, 62 per cent of the doctors surveyed believed the practice to be ethically acceptable, and were happy to recommend or prescribe placebo treatments.
While the most commonly used placebo treatments prescribed in the past year were over the counter painkillers or vitamins, some doctors reported using antibiotics and sedatives as placebos.
Only three per cent reported using sugar pills.
Most doctors even said that they typically described the placebo treatments to patients as "a potentially beneficial medicine or treatment not typically used for their condition", only rarely did they admit to explicitly describing them to patients as "placebos".
The authors are of the opinion that prescribing harmless treatments like vitamins or over the counter painkillers to promote positive expectations without full disclosure of motivations might not raise alarm bells, but prescribing antibiotics and sedatives when there is no clear medical indication could have serious adverse consequences for both patients and public health.