A common blood pressure pill could help treat phobias and post-traumatic stress
Phobias and post-traumatic stress could be banished for good by taking a commonly prescribed drug for blood pressure.
Previous studies had suggested that people who experienced traumatic events such as rape and car crashes showed fewer signs of stress when recalling the event if they had first been injected with the beta blocker propranolol, but it was unclear whether the effect would be permanent or not. Fearful memories often return, even after people have been treated for them.
To investigate whether propranolol could stop fear returning in the longer term, Merel Kindt and her colleagues at the University of Amsterdam, the Netherlands, conditioned 60 healthy students to associate a picture of a spider with an electric shock, so that they would eventually be startled by the picture even in the absence of a shock.
However, if the conditioned students were given oral propranolol before seeing the picture, their startle response was eliminated. What's more, it didn't return when the students were put through a second round of conditioning that should have reinstated their fear - suggesting that the association may have been permanently broken.
Those given a placebo pill could eventually be trained not to be startled by the spider picture, by repeatedly showing it to them in the absence of a shock.
A similar technique is often used in phobia clinics - exposing people with arachnophobia to spiders in a safe and calm environment, for example. However, "even after successful treatment of anxiety disorders many fears and phobias come back," says Kindt.
When those in the placebo group were given a series of electric shocks, their fear of the spider also returned, while those in the propranolol group continued to react calmly to the spider picture, suggesting that the association may have been permanently erased, or at least negated to such a point that it has no effect.
When people experience traumatic events, the body releases adrenaline - also called epinephrine - which affects an area of the brain involved in emotional processing called the amygdala, and makes an emotional connection to the memory.
Reliving the memory triggers further release of adrenaline, reinforcing the memory still further. Since propranolol blocks adrenaline receptors in the amygdala, Kindt believes it may also block this reinforcement process and break fear association.
"We can't prove that the memory has gone away, but it is at least weakened so much that we can't find it anymore," says Kindt.
However, Chris Brewin, a memory expert at University College London, UK, says the findings are interesting, but cautions that Kindt's group only tested the volunteers over the course of three days.
"The fear might come back if they tested them several weeks later," he says.
Also, Kindt only looked at the degree to which the volunteers were startled - but conditions like post traumatic stress disorder often involve other emotions such as anger and shame, and we don't know how propranolol would affect them, he says.
Journal reference: Nature Neuroscience