When going to the GP, most people expect to leave with medication to fix an illness — or at least a treatment plan to tackle it.

But Australian-first research reveals doctors are instead giving many patients placebos, ranging from water-based injections to unnecessary antibiotics.

Key points: 77 per cent of doctors reported giving 'active placebos' — drugs that are real but aren't used to address the underlying condition

77 per cent of doctors reported giving 'active placebos' — drugs that are real but aren't used to address the underlying condition 39 per cent of doctors give 'inactive placebos' — fake drugs, like sugar pills

39 per cent of doctors give 'inactive placebos' — fake drugs, like sugar pills GPs report using placebos because they believe they have genuine psychological benefits

A placebo treatment is one doctors know won't address the underlying condition but that may produce a positive psychological or physiological effect for some patients.

University of Sydney School of Psychology Associate Professor Ben Colagiuri said almost 80 per cent of Australian GPs reported giving patients an "active placebo".

"Many were prescribing antibiotics or antidepressants, which are genuine drugs, as a placebo," Professor Colagiuri said.

In other words, many patients are being prescribed real medications — but these medications are not designed to treat the condition the patient presented with.

In the study of 136 GPs across Australia, 77 per cent admitted ever giving active medications such as antidepressants as a placebo and 40 per cent said they used them at least once a month.

A total of 39 per cent of doctors said they gave inactive placebos — like sugar pills.

The patients most likely to receive a placebo were those presenting with a viral infection, insomnia, pain, fatigue or depression.

"Doctors generally do not tell patients what they are getting is a placebo and genuinely think patients would benefit from it," Professor Colagiuri said.

Why prescribe a placebo?

Despite their lack of medical efficacy, studies show placebos can actually help patients suffering from pain, nausea and high blood pressure.

They can offer real benefits, often because patients expect the treatment to work.

"We know if someone is given a painkiller and they expect pain relief, there are changes in the central nervous system," Professor Colagiuri said.

"The brain releases opioids which are natural painkillers and there is a measurable response to pain."

But experts stress that while placebo treatments might help symptoms of an illness, they won't cure a serious condition such as heart disease or asthma.

What they can do, however, is to reassure patients their condition is being managed.

An example is offering melatonin, a hormone that helps regulate sleep cycles, to a patient complaining of insomnia, even though it is not clear whether it will help.

Dr Cris Beer, a GP on the Gold Coast, said doctors may offer a placebo to reassure patients and avoid giving them riskier medication.

"Meeting patient expectations for something they can hopefully use to help them settle their anxiety and be able to fall asleep is better than giving them nothing and letting them lie wide awake," she said.

In some instances, placebos can prevent doctors putting patients on stronger medications, such as sleeping tablets.

"Unfortunately, you then have the situation where a patient can become addicted to them and that's creating more problems to try and get them off," she said.

Too much pressure on GPs?

In a survey of Australian doctors, Associate Professor Ben Colagiuri found more than one third had given patients inert placebos. (Supplied: University of Sydney)

The study revealed 40 per cent of GPs suggested a placebo, because it was what patients expected.

In one instance, Dr Beer said she had been verbally abused by an aggressive patient when she would not offer him medicine for a cough she diagnosed as a viral infection.

"They've come to see you and so you feel in some way obligated by the pressure of meeting patient expectations for something at the end of the consult," she said.

More than half of doctors offered placebos because they believed they would deliver genuine benefits.

Dr Beer said antibiotics were one of the most commonly prescribed active placebos, particularly where patients had a viral illness.

The study found one in five GPs reported prescribing antibiotics for suspected viral infections.

Australian Medical Association vice-president Chris Moy said placebos could be appropriate in some cases.

"In exceptional circumstances where everything else has failed, and where there is no risk to the patient, you are not going to do any harm, a doctor may consider prescribing a placebo, and guess what if it works, the proof is in the pudding, it's been a success," Dr Moy said.

He said there was striking evidence of the therapeutic benefits of some placebos.

"The studies show somewhere [between] about 15 to 70 per cent of times giving a placebo may alleviate symptoms," he said.

Fewer than 200 GPs took part in the study, with the study authors cautioning that the findings may not be applicable to all GPs in Australia.