March 11, 2009
Propranolol Permanently Reduces Human Fear Response

There's nothing to fear but fear itself - and even that can be eliminated with a drug treatment.

A team of Dutch researchers under the leadership of Vici-winner Merel Kindt has successfully reduced the fear response. They weakened fear memories in human volunteers by administering the beta-blocker propranolol. Interestingly, the fear response does not return over the course of time. Top journal Nature Neuroscience published the findings on 15 February 2009.

Until recently, it was assumed that the fear memory could not be deleted. However, Klindt's team has demonstrated that changes can indeed be effected in the emotional memory of human beings.

The researchers found that if they caused humans to remember a fearful memory (seeing a picture of a spider and at the same moment feeling pain) and administered propranolol that reduced the fear response when spider pictures were shown again at a later date.

The memory of connections between two events were still recallable but no longer elicited the feeling of fear.

Interestingly, after the treatment with propranolol and memory reactivation, fear memories can no longer be recalled by means of a much-used method in which the individual pain stimuli are readministered. This indicates that the anxiety memory is either completely erased or could no longer be found in the memory. It should be noted, however, that the human volunteers could remember the association between the spider and the pain stimulus but that this no longer elicited any emotional response. In the next phase of the research, Kindt and her colleagues shall investigate the long-term effects of administering propranolol.

Got any fear response you want to dampen down?

I wonder what would happen if people were shown a politician's picture while someone described a policy that they feared. Would they lose their fear of higher taxes or their fear of a reduction of the welfare state? Could people be conditioned to accept (or object less strongly to) policies that they currently oppose? Could captured spies get treated with propranolol to reduce their fear of what happens should they divulge secret information while undergoing interrogation?

Update: In rats the drug RU38486 blocks the effects of stress hormone cortisol and reduces stress-related memories.

Philadelphia, PA, 17 March 2009 Imagine that you have been in combat and that you have watched your closest friend die in front of you. The memory of that event may stay with you, troubling you for the rest of your life. Posttraumatic stress disorder (PTSD) is among the most common and disabling psychiatric casualties of combat and other extremely stressful situations. People suffering from PTSD often suffer from vivid intrusive memories of their traumas. Current medications are often ineffective in controlling these symptoms and so novel treatments are needed urgently. In the February 1st issue of Biological Psychiatry, published by Elsevier, a group of basic scientists shed new light on the biology of stress effects upon memory formation. In so doing, they suggest new approaches to the treatment of the distress related to traumatic memories. Their work is based on the study of a drug, RU38486, that blocks the effects of the stress hormone cortisol.

Using an animal model of traumatic memory, investigators at the Mount Sinai School of Medicine show that treatment with RU38486 selectively reduces stress-related memories, leaving other memories unchanged. They also found that the effectiveness of the treatment is a function of the intensity of the initial "trauma." Although this particular study was performed in rats, their findings help to set the stage for trials in humans. Cristina Alberini, Ph.D., corresponding author on this article, explains how their findings will translate into developing clinical parameters: "First, the drug should be administered shortly before or after recalling the memory of the traumatic event. Second, one or two treatments are sufficient to maximally disrupt the memory. Third, the effect is long lasting and selective for the recalled memory. Finally, the time elapsing between the traumatic experience and the treatment seems to be an important parameter for obtaining the most efficacious treatment."

Drugs that selectively eliminate some of our memories and emotional reactions appear to be well within the realm of the possible. Therefore we'll have such drugs some day.

Share |      Randall Parker, 2009 March 11 11:22 PM  Brain Emotion Alteration

Faruq Arshad said at March 12, 2009 6:50 AM:

Surely someone else must have thought that the fear response serves a useful purpose under certain circumstances? After taking this drug people might become more risk-prone?

Bob Badour said at March 12, 2009 7:44 AM:

I take propranolol for other reasons. It doesn't make me particularly risk prone. Probably less risk prone overall.

David Govett said at March 12, 2009 10:37 AM:

Soldiers will be taking this. And newlyweds.

Randall Parker said at March 12, 2009 8:39 PM:


The drug suppresses specific previously learned fear responses. I do not expect it will disable your ability to learn new reasons to feel fear. Also, the use of the drug probably must be coupled with a particular memory recall. If you don't remember every scary situation of your life while taking the drug most of those fear responses will remain.


Women will slip it into drinks of boyfriends who claim they are afraid to get married.

Nick G said at March 13, 2009 11:08 AM:


Much of human misery is caused by irrational fear. This drug would seem to be A Really Big Deal - the answer to human progress in personal life and for dealing with Big Questions like PO and AGW.

Sure, you have problems like getting people to take it, when they don't recognize that they're operating from fear rather than rationality, but still, it seems like A Really Big Deal.

What do you think?

Randall Parker said at March 13, 2009 7:42 PM:

Nick G,

Irrational fears and human misery: I think many other cognitive phenomena cause more misery:

- Low IQ.
- Innate cognitive biases (I think there's another term for this) that cause erroneous recurring mistakes in processing data.
- Impulsiveness.

You can take away fears and people will still screw up.

Besides, people won't choose the right fears to extinguish. The ability to extinguish fears might do more to enable personally destructive behaviors than to enable people to do beneficial things they now fear to do.

Nick G said at March 17, 2009 2:37 PM:


I think both genetics and culture/psychology are essential to understanding behavior.

Personally, I think that unconscious fear is much more important than people realize.

Let's take the example of fear of dogs. In my observation, fear of dogs is taught to children by their parents by their reactions to dogs. If an approaching dog causes a parent to swoop up their child and reassure it, accompanied by parental anxiety (to which children are very sensitive), children learn from this. As adults, they don't perceive themselves as afraid of dogs, they simply see dogs as dangerous. They externalize it.

I have no doubt that this phenomena depends on genetics: we must be vulnerable to this kind of fear conditioning. Some people will be more or less vulnerable, and possibly responses will depend on the source. Apparently Propanolol gives us a way to interrupt this physiological process.

Many group fears are like this: of other races, countries. Of Isrealis toward Palestinians, and vice versa. I'd love to see what would happen in the ME if someone put Propanolol in the water supply.

"The ability to extinguish fears might do more to enable personally destructive behaviors than to enable people to do beneficial things they now fear to do."

On the whole, I trust people's higher level cognitive judgement better than their lizard-brain fears. Conditioned fears may be useful for children whose parents don't have the resources to provide safe surroundings, and people facing primitive problems, like predators, but I think they're much less useful in modern complex society.

an0n said at October 25, 2012 3:03 AM:

Holy crap, they put Buddha in a pill.

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