The findings could open the door to long-term treatments for patients with emotional disorders.

Around 10 million people in the UK have a phobia and an estimated 3.5 per cent of the population will be affected by post-traumatic stress.

Previously, it has been suggested that beta-blockers could be used to help calm nervous air travellers.

What is the research?
The findings build on earlier studies in animals which showed that beta-adrenergic receptor blockers could interfere with how memories are stored.

The researchers created a fearful memory in each of the 60 study participants, aged 18-28, by associating pictures of spiders with a mild electric shock delivered to the wrist.

The following day, the participants were randomly assigned to receive either 40mg of propranolol or a placebo.

The participants were then subjected to the spider pictures again.

The researchers evaluated how fearful the participants were by recording their startle response to sudden loud noises and by measuring how strongly they blinked, a measure of fear.

Initially, no difference in fear was found between the propranolol and placebo group.

However, they found that the participants who were given propranolol showed a decrease in startle response 24-48 hours after they had been given the drug compared with participants who were given placebo.

What do the researchers say?
Lead researcher Dr Merel Kindt from the University of Amsterdam, told GP that the study was not about erasing memories but about being able to eliminate the fearful response to a specific stimulus, such as a spider picture.

'The media has blown our study out of proportion.

'There is nothing special about the drug propranolol. It is a common beta-blocker that is prescribed by GPs every day. Only if it is used in a very specific therapeutic context may it reduce the fear responses.

'The procedure described in the paper is in a highly experimental stage and is only a proof of principle. It will probably take several years before it is applicable in clinical practice.'

In the meantime, GPs should not start prescribing propanolol for anxiety disorders as it is not an anxiety drug, warned Dr Kindt.

What do other researchers say?
Paul Farmer, chief executive of the mental health charity MIND said: 'We would need much more research into the risks and benefits of this treatment before it becomes a reality.'

Dr Daniel Sokol, lecturer in medical ethics at St George's Hospital in London, added that removing bad memories was not like removing a wart or a mole.

'It will change our personal identity since who we are is linked to our memories,' he said.

Informing Patients

Beta-blockers could be used to treat patients with post-traumatic stress. Further research is needed to build on this small-scale study. Ethics experts warn that tampering with memories could affect an individual's personality.

sanjay.tanday@haymarket.com

• Nature Neuroscience Online 2009