The placebo response as a form of classical conditioning

I have already written a few posts about the pros and cons of The placebo effect. The placebo effect can loosely be defined as the effects you get when you think you are receiving medical care, be it psychological counselling or an injection of some substance.

I have also written previously about classical conditioning (see for example Learning described at the cellular level: Finding from our laboratory in Lund). Classical conditioning is a type of learning in which you pair a neutral stimuli such as a tone, a light, a touch, a picture, a thought or something else with another stimulus that has an associated reflex such as a puff of air in the eye (causes you to blink), a punch in the face (also causes you to blink), an electrical shock (causes fear and pain), or a shot of morphine (causes you to enter heaven for a short while).

If you present a neutral stimulus to someone and then, directly afterwards a reflex eliciting stimulus to the same person, and then repeat this procedure many times, then you will eventually notice that merely presenting the neutral stimulus can cause the person to perform the reflexive behavior that was formerly associated only with the second stimulus.

For example, play a tone just before giving an air-puff to the eye of your participant, over and over again, and you will eventually see that the participant blinks when he or she hears the tone. Show someone a picture just before you give that person an injection of morphine, and eventually (after a number of repetitions), that person will feel as if he or she was in heaven just from looking at the picture.

I don't know whether the relationship between the placebo effect and classical conditioning has become obvious to you yet, but if not, let me spell it out. Say that you have a spinal injury causing permanent and intensive pain. In some cases the only available therapy is regular morphine injections. You go to your doctors, enter the hospital, the doctor takes out an injection needle, and sticks it through your arm into a vein and injects a fluid which contains morphine. Notice that all these experiences leading to up the injection of the morphine can work as a neutral stimuli that is consistently associated with an injection of morphine. In other word, it is likely that one of these neutral stimuli such as seeing the injection needle (just like seeing a nice steak will cause an increased saliva production (at least for me)), will start processes in your body similar to the ones you experience when you get the actual morphine injection.

This was a hypothetical example for which I have no reference, however, you can find examples in the scientific literature which quite strongly supports the idea that placebo's sometimes are a form of classical conditioning.

For example it has been shown that people who are allergic to pollen, can get allergic reactions just from seeing a flower, even if it is made of plastic and therefore has no pollen.

In a more extreme example, a boy was getting chemotherapy to treat his cancer. The chemotherapy was paired with a specific taste and smell. Later on, the boy was presented with only the taste and smell and surprisingly (or not), the doctors observed the same effects as during the "real" chemotherapy...

These results have all but convinced me that there is indeed many parallells between the placebo effect and classical conditioning. Further these findings do suggest that you can help patients quite a lot without actually giving them "real" medicine. However, I also think it is wise not to go to far with this (see again: The placebo effect).

At the very least, this is a truly fascinating subjects that I, for one, will continue to follow.

See also my post on Complementary and alternative medicine - Spontaneous recovery from disease

Complementary and alternative medicine - Spontaneous recovery from disease

Alternative and complementary medicine refers to products and practices which are not part of the standard medical procedure that you get when you go to a hospital. Though the terms are often used interchangeably, alternative refers to when a practice aspires to replace standard medical care whereas complementary practices only aspire to complement standard medical procedure. For sure, for sure, medical research is far from a complete understanding of the physiology and anatomy of humans, and there are almost certainly many effective remedies which are not a part of the standard repertoire today. In the future we will no doubt see many advances in science and in consequence, new therapies to treat disease.

Having said this, complementary and alternative medicine suffers from what I consider to be a much more serious problem. First of, many of the techniques and practices used in alternative and complementary medicine have never been tested, or have not gained any support, in controlled studies and hence they have never proved to have any "real effect" (as opposed to placebo effect which they probably do have). Even more serious, because alternative therapies have often not been tested properly, it is hard to tell whether they have any serious side effects. What is almost certain is that if a particular substance has any effect at all, then it is more than likely to have side effects as well (see table at bottom of this article).

Sometimes alternative practices turn out to be effective and when they do they are eventually assimilated into standard medical practices. To be fair, this assimilation process can sometimes be agonizingly slow and some doctors are probably too conservative, however, the essence of the matter is that when an alternative treatment or therapy has gained enough support in studies it will cease to be "alternative" and become "standard". This is to some extent true for acupuncture, which is now used occasionally as a treatment for various conditions even though it has long been controversial. However, importantly, the mechanism that makes acupuncture work seems to be different from what has been claimed by those who have used this procedure in the past. No meridians have ever been demonstrated. Instead it seems that acupuncture stimulate pain sensing nerve endings. These nerve endings in turn exercise a form of lateral inhibition meaning that they block other pain sensing nerve endings around them, thus preventing the patient from experiencing pain in that area.

Complementary and alternative practices can often give the illusion of being effective because we recover spontaneously from diseases. We have an impressive immune system, which deals with seemingly limitless pathogens in an extremely efficient and competent manner. I am making up the numbers here, but say that after taking a certain herb 90% of all people recover from the flue within a week. Wow, surely there must be something to it then? But wait a minute. Almost everyone (say 90%) recovers from the flue within a week if they just stay home in bed. Suddenly these herbs do not seem that fantastic, and they seem even less attractive if you take into account the often excessive price tags.

Back pain is another example that deserves mention, and these figures I am not making up (they come from a lecture I attended recently). Nine out of ten (90% that is) cases of acute back pain will go away after one week. Combine this with the fact that 60-80% of all individuals will experience back pain sometime in their lifetime and what you get is an awful lot of cases of back pain that goes away in one week. Not surprisingly, at least not to a cynic like me, there are a huge number of alternative or complementary therapies for back pain, and they all seem really successful as long as you do not compare them to no treatment at all…

Here is my advice, my alternative therapy if you like. If you experience back pain, and don't have any other serious symptoms such as your vertebrae penetrating your back muscles (in which case I would advice going to a doctor), don't spend your money on all sorts of alternative/complementary therapies, rather relax for one week and see if the pain simple goes away (in most cases it will). Once you have recovered, use the money you would have spent on a therapy on something nice, such taking your girlfriend to a cozy restaurant. If the pain does not go away after one week, go see a doctor and have your back checked up…

Writing about alternative medicines is something that really warms my heart. I have written about homeopathy here, here and here, and here I have written about the role of the placebo effect.

The placebo effect

As far as I can remember I have always been opposed to, or at least skeptical towards the use of medicine that has not been properly tested and compared to placebos . I think that medicines should be tested extensively before they are released on the market. If you will, I am a bureaucrat in these matters, but why? Before I dwell further into this it is probably good with a definition of the placebo effect, here is one:

"A physical or emotional change, occurring after a substance is taken or administered, that is not the result of any special property of the substance. The change may be beneficial, reflecting the expectations of the participant and, often, the expectations of the person giving the substance."

But this sounds great does it not? If this is true then we can stop all administration of conventional medicine and thereby avoid all the associated side effects. As long as we can convince patients that water will heal them, it will, right? Just as a parenthesis, I think this is how homeopaths achieve their results. They are after all administering water with no active substance left in it.

The problem with a heavy reliance on placebos is that people would have to have a certain state of mind in order for a placebo to have any effect. Perhaps it is possible to create this state of mind by saying, for instance, that water will cure whatever it is the patient is suffering from. However, if this deception became a standard medical procedure I think that in the end people would cease to believe the doctors and then the placebo effect would disappear, and we would have no effective cures. Now some will probably object and say that it is not deception, but I think it is. If they were honest they should say that the medicine might have an effect, depending on whether you believe in it or not, and that is different. Similarly, if doctors would, on a large scale, tell their patients that they were getting for instance Prozac when in fact they were only given sugar, then this scam would eventually be detected and people would start to distrust their doctors which would diminish the placebo effect. In sum, apart from requiring doctors to lie to their patients, using placebos on a large scale would only achieve results for as long as doctors were able to keep their deception in the dark.

In the above I have tried to reserve some space for a few positive words. It should be clear by now that placebo effects are dependent on the state of mind of the person taking the placebo, it is not an intrinsic property of the substance that is taken. This means that certain therapies, such as for instance homeopathic medicine, will work on some people (probably those who believe in it) but not on others. Thus if we were to analyze the set of beliefs that a particular patient has then it should be possible to give that patient whatever he or she believes in and achieve an effect. In essence I am saying that if someone believes that acupuncture will achieve miracles, then give them acupuncture, or if someone thinks that homeopathic medicine is good against headaches, then, by all means, give them their homeopathic substances. However, because the placebo effect is rarely as strong as the effect of conventional medicine, I think this approach should be confined to less serious conditions.

I see one further application or lesson from the above. I think that doctors should do their best to encourage their patients. Make them feel good, and tell them that they can help themselves in the healing process (not a lie). I think that a lot could be achieved by giving patients a sense of their intrinsic ability to heal themselves. The first essay I wrote at Lund University was about this. If you are interested you can read it here.