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Pleasure and Pain
Pleasure-Seeking Behaviour
Pleasure and Drugs
Avoiding Pain

HelpLink : One in five live with chronic painLink : Chronic Pain - Hope through researchLink : Treat pain more aggressively, experts insist
Link : Un adulte canadien sur cinq souffre de douleurs chroniquesLink : About Suffering : FOR A NEW APPROACH TO SUFFERING, PHYSICAL AND MENTALLink : Pain and the Dying : the Hospice Movement And the Work of Cicely SaundersLink : What Are The Most Common Types Of Chronic Pain?
Link : Les affres de la douleurLink : Canadian Pain CoalitionLink : premier colloque francophone sur la douleur chroniqueLink : Book : Repenser la douleur. Sous la direction de Pierre Beaulieu
Link : Pour ne pas remplacer une douleur par une autre : Des chercheurs s'attaquent à la douleur chronique consécutive aux chirurgies cardiaquesLink : Les douleurs chroniques perturbent la vie et le sommeilLink : Bay Area Pain Medical AssociatesLink : La société canadienne de la douleur
Link : Pain Relief 4 You After Surgery
Researcher : Serge Marchand, de l'UQAT / UdeSResearcher : Michael SalterResearcher : Yves De Koninck
History : Relief of Pain and Suffering

In 25% of all cases where people go to see their doctors because of pain, that pain is chronic, which goes to show just how prevalent chronic pain is. Back pain is the leading type of chronic pain, followed by headaches, pain in the joints, and then a wide range of various types of chronic pain in the abdomen, the chest, and other parts of the body.

The statistics on chronic pain are staggering. The International Association for the Study of Pain reports that about 20% of the world’s population —one out of every five people—suffers from chronic pain.

According to the most conservative estimates, in the United States alone, about 50  million people experience chronic pain, and the resulting costs of treatment and lost productivity run to about $125 billion each year.

Chronic pain affects the same proportion of the population in Canada and Europe as well, and its prevalence increases with age. According to one pan-Canadian study, in Quebec, the prevalence of chronic pain among men and women over age 65 is nearly 40%.

In Europe, 75 million people have been living with pain for more than seven years, and one-fifth of them for over 20 years without having managed to find the relief they need. As a result, 21% of these people living with chronic pain have also been diagnosed with depression.

In 2004, a survey by the American Chronic Pain Association showed that more than half of all people with chronic pain regarded their ability to work as compromised. The Chronic Pain Association of Canada reports that people who have chronic pain miss an average of 16 days of work per year.

About 45% of all people with chronic pain experience a deterioration in their personal relationships as a result. Hence it is no surprise that, according to a study published in January 2006, nearly 14% of all Quebeckers who have chronic pain make a suicide attempt. In this case, the problem is not so much a lack of effective treatments as a lack of resources to provide them and of adequate access to them. For example, statistics published in 2005 indicate that at that time, at least 4 500 Quebeckers with chronic pain were waiting for their initial assessment in a specialized pain clinic, and two-thirds of them had been waiting for more than nine months.

Link : Association québécoise de la douleur chronique : statistiquesResearcher : Philippe SarretLink : Common Pain Problems

The pain associated with cancer can be either acute or chronic. Acute pain can result from cancer treatments (surgery, chemotherapy, radiation therapy), while chronic pain can occur, for example, when the tumour presses on a nerve, or releases certain chemicals, or interferes with the flow of blood or the functioning of internal organs.

Various data seem to indicate that the pain caused by cancer has a negative effect on the immune system, which could indirectly encourage the growth of the tumour. That is one reason why it is so important for both the acute pain and the chronic pain associated with cancer to be treated immediately.

Link : Types and causes of cancer pain

In times past, various thinkers saw the purpose of pain as being to heal, or to punish, or to ennoble. But today’s scientists see it differently: for them the purpose of pain is to alert us that a part of our body has been damaged or is in danger of being damaged.

This warning function unquestionably has adaptive value, but it is performed only by acute pain, as opposed to chronic pain caused by pathological conditions.

As the terms “acute pain” and “chronic pain” suggest, the main criterion for making this distinction is the duration of the pain. Acute pain may last anywhere from a few seconds to several months, but eventually it disappears once the healing process is completed. In contrast, pain is regarded as chronic if it persists beyond the normal healing time and continues for more than three to six months (though it may change in some ways over this time). Chronic pain can result from an injury that does not heal properly, or from a host of other causes, such as cancer, nerve damage, or arthritis.


Detail of Andromache Mourning Hector, by Jacques-Louis David, 1783, oil on canvas, Musée du Louvre, Paris

But before venturing into the complexities of chronic pain, let’s discuss acute pain in more detail. Acute pain consists of sharp, immediate sensations of pain in response to a specific tissue injury. Acute pain is highly localized and is accompanied by autonomic reactions (such as sweating and increased heart and respiration rates) and motor reactions (such as the withdrawal reflex).

Acute pain can range from the simple pain of an insect bite, to post-surgical pain, to pain from an infection, burn or fracture, which may last for several months. But in all cases, acute pain is a symptom that gradually fades away as the illness is cured or the wound heals.

But sometimes pain becomes chronic. In such cases, pain no longer seems to have any connection with its primary function of protecting the body, and there is no longer any clear relationship between the nature of the physical injury and the intensity of the pain. Chronic pain inevitably degrades people’s quality of life and can even alter their personalities, interfere with their work, and affect their personal relationships.

Living for more than six months, or sometimes even several years, with a chronic backache (see box below) or recurrent migraines can be extremely disabling. In the worst cases, people can no longer perform routine tasks, because it is so hard for them to concentrate on anything besides their pain. Chronic pain can lead to insomnia, anxiety, anger, distress, and even depression.

When people are in chronic pain, depression can amplify it, thus depressing their mood even further. Everything possible should be done to prevent this vicious cycle through appropriate treatment—people who suffer from depression in conjunction with chronic pain generally respond fairly well to antidepressants—but such treatment is not always provided, because of the misconception that anyone who is in constant pain must necessarily be depressed.

Even worse, there was a time, unfortunately not so long ago, when many people who complained of chronic pain (see sidebar) were regarded as hypochondriacs or attention-seekers. Now we know that these views were wrong, and that chronic pain is a genuine disease, a distinct disorder of the nervous system, produced and maintained by a variety of abnormal cellular processes.

Chronic pain comes in many different forms. It can recur intermittently, as in the case of migraines, or it can be constant while varying in intensity, as in the case of backache (see box below). But chronic pain caused by degenerative diseases such as rheumatoid arthritis and cancer can not only be constant but also grow continuously more intense as the disease progresses (see sidebar).

Chronic pain can also set in when an accident, an infection, or a surgical operation damages a nerve so that it keeps sending out pain signals even though the the original injury has otherwise healed completely. This type of pain that originates basically in the nerve cells themselves is known as neuropathic pain.


Back pain is certainly one of the most common kinds of pain. In fact, it is the top reason that people visit specialized pain clinics. The statistics on back pain are telling. About 80% of all adults will experience back pain at some time in their lives. Back pain is the leading cause of disability in adults under 45 years of age and the leading cause of work absences lasting less than 15 days. Back injuries account for 25% of all disability benefits paid out by insurance companies. Indeed, back pain seems to be one of the most common ailments of our age.

Back pain can be highly disabling, limiting people’s activities of daily life and generating stress, which is itself an aggravating factor in back pain. Given that each of us needs to bend our back some 1 500 to 2 000 times per day, the importance of breaking this vicious cycle as quickly as possible becomes readily apparent.

But why are our backs so vulnerable in the first place? The first thing to remember is that they are complex assemblies of bones, nerves, muscles, tendons, and ligaments, all of which can produce pain. Second, from childhood on, all of us subject our backs to various kinds of abuse—carrying too many books to school in our backpacks, not getting enough exercise, enduring too much stress, performing exhausting, repetitive physical work, and so on.

More specifically, the back is a framework of bones—the spinal column—that surrounds and protects the spinal cord. The spinal column consists of 24 vertebrae (7 cervical, 12 dorsal, and 5 lumbar) separated from each other by intervertebral disks that serve both as joints and as damping cushions. This complex mechanism is our inheritance from the evolution of the four-legged vertebrates who preceded us, yet we demand that it do the hard work of maintaining our upright posture as bipeds.

Unsurprisingly, some pieces of this puzzle can sometimes shift slightly out of place, thereby causing back pain. Back pain can occur in each of the three major anatomical areas into which the back is divided. Thus we speak of cervicalgia (pain in the neck and upper back), dorsalgia (pain in the mid-back), and lumbalgia (pain in the lower back, which is the commonest of the three).

Back pain can arise, for example, when you remain too long in an abnormal position, such as leaning forward or sitting or lying down in a poor posture. This places an overload on your ligaments, muscles, and disks. Another common source of back pain is when you wrench your back or “throw it out of place” by making an awkward movement, often one that involves twisting the torso.

We are not talking here about major displacements of the spinal column, such as can occur in highway accidents and cause significant damage to the spinal cord. Instead we are talking about cases where the shift in the position of the vertebrae is very small but nevertheless reduces their mobility. Quite often, this lack of mobility causes contraction of the muscles nearby, thus further increasing the pain.

Your back can also be damaged if you make repeated movements in an awkward way, or carry loads that are too heavy for you. Too much pressure on the spinal column can force part of a disk out beyond its normal boundary, resulting in what is called a herniated disk. The herniated disk may then in turn compress a nerve root and produce referred pain in an arm or leg (see sidebar). Leg pain caused by a pinched nerve root in the lumbar spine is known as sciatica. The vast majority of herniated disks occur in the lower back, and they account for about 2% of all cases of back pain.

Some of the pathologies that cause back pain, such as herniated disks and osteoarthritis, can be readily identified with x-rays. But in the vast majority of cases, doctors cannot find any signs of what is causing the back pain, even with x-rays and other diagnostic scans. What is more, in 90% of all patients, these pain symptoms fade away on their own in less than a month or two.

That said, if your back ever really starts to bother you, you are best advised to go see a doctor, before the pain becomes chronic. Your doctor can give you some simple rules to follow to prevent back pain: exercise regularly to maintain good muscle tone in your back; when lifting anything heavy, bend at the knees instead of with your back; avoid carrying anything too heavy; and avoid any activities, such as jogging, that generate repeated jolts to the spinal column—instead, engage in exercises such as swimming, which stretches your back muscles and tones them at the same time.

You should also avoid sitting for too long at one time. A review of 25 studies has shown that working at a computer does not cause lower-back pain, if you sit in the proper position. But the frequency of lower-back pain does seem to increase if you sit for a long time in a bad position or while being subjected to vibrations. The risks of back pain are thus 5 times higher among truck drivers and 9 times higher among helicopter pilots than among the general population.

Link : Back painLink : Common causes of back painLink : Back PainLink : Back PainLink : Douleur du dos - Pourquoi souffre-t-on ?Link : Mal de dos
Link : Prévention des douleurs de dosLink : Dix règles pour mieux travailler sur ordinateurLink : SciaticaLink : Hernie discaleLink : LA SCIATIQUE AR HERNIE DISCALEExperiment : Workplace stress, lifestyle and social factors as correlates of back pain : a representative study of the german working population


Pain is sometimes felt at a different place on the body from the one where there is actually a problem. This phenomenon is referred to as projected or referred pain.

One common example is when you bump your elbow, then feel a pins-and-needles sensation in your ring finger and your pinky. The explanation is that you have compressed the ulnar nerve, which passes through your elbow. This compression generates a series of nerve impulses that go back up the the spinal cord and make you feel as if the pain is in those fingers. The same phenomenon is at work when irritation of the sciatic nerve at the level of the lumbar vertebrae makes you feel pain in your legs. Likewise, an irritated or spasmed muscle in your neck can give you a headache.

Another classic example of referred pain is the pain that people feel in their left arm or shoulder when they are having an attack of angina. In this case, the actual problem is in the heart, which is not receiving enough blood, but the pain is experienced in another part of the body, in addition to often being experienced directly on the left side of the chest.

Other diseases of the internal organs can cause the same kind of confusion. A pain in the bile duct, for example can be projected into the back. Or a pain that originates in the kidneys, digestive tract, or vertebrae can be projected to the testicles.

In many cases where the viscera (internal organs) are the source of the referred pain, the explanation lies in what is known as viscero-somatic convergence. The internal organs have very few dedicated pathways for carrying pain signals up the spinal cord to the brain. Most of the nociceptive pathways from the viscera converge on the same medullar dorsal horn neurons that receive the nociceptive pathways from the skin. The hidden cost of the body’s saving resources in this way seems to be the confusion that can result as to the actual location of the pain.


Link : L'effet placebo: pas juste dans la têteLink : Deconstructing the Placebo Effect and Finding the Meaning ResponseLink : Commercial Features of Placebo and Therapeutic EfficacyLink : Alcool et violence: un lien jusqu'où?
Link : Décortiquer l'effet placebo pour mieux l'utiliserLink : Radiolab : PlaceboLink : L’effet placebo et ses paradoxesLink : Overt versus covert treatment for pain, anxiety, and Parkinson's disease
Link : A message in a bottle: Extrapharmacological effects of alcohol on aggressionLink : Placebo et effet placebo (première partie) : définition, aspects cliniques, mécanismesLink : Concept of true and perceived placebo effectsLink : Comprendre l’effet placebo pour mieux traiter la douleur
Link : Effet placeboLink : Genetics of successful placebo response to stressLink : The Psychology of the SaleLink : Swearing increases pain tolerance
Experiment : Loss of expectation-related mechanisms in Alzheimer's disease makes analgesic therapies less effective
Original modules
Tool Module : Ethical Issues Raised by the Placebo EffectEthical Issues Raised by the Placebo Effect
Tool Module : Anesthesics and Analgesics Anesthesics and Analgesics
Experiment Module : Acupuncture and the Placebo Effect Acupuncture and the Placebo Effect
Experiment Module : The Blind Spot The Blind Spot

Science is far from having solved all the mysteries of the placebo effect. The mystery of “open placebos” is a good example: researchers openly tell patients that they are being given a sugar pill three times per day. Thus they are well aware that they are not taking any active medication, yet they nevertheless report that their condition has improved!

A similar phenomenon was observed back in the 1970s among heroin addicts, who had discovered that when they couldn’t get any heroin, they could ease their withdrawal symptoms at least somewhat simply by injecting themselves with water. Researchers observed that these individuals also displayed physiological signs, such as contracted pupils, that were similar to their responses to opiates, thus showing that conditioned responses are involved in the placebo effect.

Link : Placebo is not what you think

Just as patients’ positive expectations can improve their health (the placebo effect), their fears regarding a treatment can make their health worse, even if the treatment actually involves no active ingredient! This opposite side of the coin from the placebo effect is known as the nocebo effect (from the Latin for “I will harm”).

Just like the placebo effect, the nocebo effect is not attributable to any mental disorder, but simply to an aspect of the functioning of the normal human brain. In a study conducted at the University of Turin in Italy in 2007, two groups of men were taking a prostate medication. One group were told that the medication’s possible side effects included erectile dysfunction and loss of libido, while the other group were not. The number of men who then reported experiencing these side effects was three times higher in the first group than in the second.

Many other studies have confirmed that patients who have been informed of the possible undesirable side effects of their treatment are more likely to experience them than patients who have not been so informed. Put another way, reading the description of possible side effects on a bottle of medicine can make you sick. And just as the placebo effect is regarded as enhancing the impact of a medication, the nocebo effect is regarded as potentially accounting for a portion of the negative side effects of any active medication.

In a study in the 1960s, when ethical constraints on scientific experiments were less elaborate than they are today, subjects were given sugar water and told that it would make them vomit. The result: 80% of the subjects did in fact vomit. In another typical example of the nocebo effect, someone takes a medication knowing that its side effects can include abdominal pains, and then begins to experience such pains within the next few minutes, before his or her system has even had time to absorb the active molecule in the medication!

Here is another well known manifestation of the nocebo effect: anticipating pain increases its magnitude. Experiments have shown that such apprehension caused an increase in brain levels of cholecystokinin, a neuropeptide that is known to facilitate the transmission of painful sensations. Furthermore, when the subjects were injected with a cholecystokinin blocker, the painful nocebo effect disappeared.

In another possible instance of the nocebo effect, about one-quarter of patients who receive placebos in clinical trials complain of side effects such as headaches or sleepiness. One possible explanation is that these people simply become hypervigilant about minor discomforts that any healthy person experiences occasionally.

Symptoms such as accelerated heart rate, dry mouth, nausea, and diarrhea might also be explained by anxiety and apprehension about the possible side effects of a treatment. These symptoms are classic bodily responses to stress, and are studied as part of the broad research field known as psychoneuro-immunology (see box to the right).

Link : L'effet noceboLink : The Curse of the Nocebo EffectLink : Power of Suggestion: When Drug Labels Make You Sick
Link : Book: Meaning, Medicine and the 'Placebo Effect'Link : When words are painful: unraveling the mechanisms of the nocebo effectLink : Reverse psychology in a pill: anti-placebo



The human brain is constantly constructing a conscious mental image of the world and acting in accordance with this image. Sometimes, in constructing this image, the brain unconsciously fills in certain gaps in its perceptions—for example, filling in visual information to cover the blind spot in the retina (follow the Experiment module link to the left).

Another example of how people’s mental processes can influence their perceptions and their physiology is the way that their expectations regarding medical treatments can influence the outcome of those treatments. This is the famous “placebo effect”, which can provide people with relief even if they have not absorbed any pharmacologically active ingredient. Simply believing that a medication or other treatment is going to help can can produce very real organic changes that result in relief. But the reverse is also true: in some cases, worrying about the possible effects of a treatment can cause equally real negative symptoms. This is known as the “nocebo effect” (see sidebar).

Though neuroscientists are beginning to identify the mechanisms underlying the placebo effect, it varies greatly with the situation and the individual concerned and hence depends on many factors that are not yet well understood. These factors can, however, be classified into four main groups: the placebo object itself, the doctor providing the treatment, the patient, and the disease.

We now know that the physical and chemical characteristics of the object used as a placebo can greatly influence the size of the placebo effect.

First, the mere name given to the placebo object can influence its effectiveness. A placebo presented to the patient as morphine will relieve pain more effectively than one presented as aspirin.

Next, the physical form of the placebo object has a major influence. One study has shown that placebo capsules are more effective than placebo tablets, and other studies have shown that placebo injections are more effective than placebo pills. The size of the placebo effect thus seems to increase as the therapeutic intervention becomes more invasive.

The effects of a placebo can also be influenced by its price. Telling patients that a placebo is a very expensive medication reinforces their belief in its potency and increases its effectiveness.

The dosage of a placebo and the number of times it must be taken can also influence the placebo effect. For example, some authors have found that when the dosage of a placebo was increased, the frequency of undesirable side-effects (such as upset stomach, sleepiness, and dizziness) also increased, if the placebo was administered for several days.

The placebo effect can also interact synergistically with an actual active medication. For example, in one study, one group of subjects was given information that encouraged them to believe in the analgesic power of a placebo, while another group was given information that encouraged them not to believe in it. After both groups of subjects had taken the placebo, analgesia was observed in the group that “believed” in the placebo, but none was observed in the group that did not believe. When both groups were then given aspirin, greater analgesia was observed in the group of “believers”. The practical implication of this kind of synergy is that the placebo effect can allow the dosage of actual analgesics to be reduced.

Placebos also generally take less time to begin having an effect than active ingredients do. This is true in treating pain, but even more so in treating depression, where placebos can begin to have an effect after one or two days, whereas, in principle, antidepressants can take two to three weeks before doing so.

The amount of time required to reach peak activity level is about the same for placebos as for real medications, and sometimes even shorter.

The time that an analgesic placebo remains effective can be as much as two weeks, after which the effect diminishes gradually. However, several cases have been reported in which placebos remained effective for more than a year, notably in the treatment of panic disorder.

The doctor also plays a prominent role in the placebo effect. Some authors believe that the origins of the placebo effect lie in the asymmetry of the doctor/patient relationship. The medical ritual, the protocols that it involves, the doctor’s qualifications, and the length of the waiting list can all create a favourable impression on patients and make them believe that they will get better—the belief that is the basis for the placebo effect.

The amount of conviction with which the doctor presents the medication to the patient, emphasizing, for example, its power as a treatment, is an especially influential factor in the placebo effect.

The amount of warmth or empathy that doctors show their patients is another very important factor for maximizing the placebo effect. As is often stated quite rightly, medicine is not only a science, but also the art of treating other human beings. In this regard, it is obviously desirable for doctors to foster the non-specific benefits of the placebo effect when seeing their patients.

For example, in one study of patients who were given placebo acupuncture treatments for irritable-bowel syndrome, the researchers compared the analgesic effectiveness of “warm” acupuncture sessions, in which the therapist greeted the patients warmly, listened to them attentively, and provided lots of explanations, and “cold” acupuncture sessions, in which there were no verbal exchanges between the therapist and the patients. In both cases, the needles were inserted superficially and away from the meridians recognized by professional acupuncturists. Compared with a control group that had received no treatment at all, the group that received the “cold” placebo showed significant improvement, but the group that received the “warm” placebo showed even more.

Another famous experiment was conducted by Dr. K.B. Thomas, a family physician in England. Dr. Thomas selected 200 of his patients who were complaining of various pains that he was actually unable to diagnose accurately. He gave half of these patients a reassuring diagnosis and told them that they would get better very quickly. With the other half, he remained vague, and suggested that they come back if their pain persisted. Two weeks later, 64% of the patients in the first group had gotten better, while only 39% of those in the second group had done so.

Many authors even go so far as to conclude that the mere fact of being in a therapeutic relationship provides a placebo effect to varying degrees. This would be an example of what some have called the Hawthorne effect, in which subjects’ simply knowing that they are being studied or listened to causes favourable changes in them. In the Hawthorne study, the changes involved increased productivity among assembly-line workers, but they can also involve improved health, as in the placebo effect.

The third main set of factors on which the placebo effect depends involve the patient. It is hard to identify any personality traits that would define a type of patient who always responds to placebos. This probably indicates that an individual’s response to placebos depends on many factors besides a simple personal predisposition.

That said, patients’ expectations with regard to a given treatment have a great influence on the occurrence of a placebo effect. These expectations are so important that if, for example, a patient questions the effectiveness of a proposed operation that might alleviate his or her chronic back pain, some doctors will try to avoid this surgery.

A patient’s beliefs can also influence the effectiveness of a particular placebo. In one study, for example, a group of subjects who believed in supernatural beings responded better to the placebo effect of floral essences if these essences were presented as being somehow associated with such beings than if they were presented simply as medications produced by the pharmaceutical industry. And the reverse was found to hold true for subjects who were more rationalist and skeptical.

Lastly, as regards the fourth set of factors, the nature and intensity of the disease can influence the placebo effect. Diseases that have a large psychosomatic component have a greater chance of responding to the placebo effect, as do diseases that cause intense suffering along with a great desire to see it disappear. The placebo effect is also more pronounced with disorders that have a large subjective component, such as depression, anxiety, or pain.


Researchers have two main strategies that they can use to assess the effectiveness of a medication. The first is to eliminate its specific effect by administering a tablet that is presented as the medication but does not contain its active ingredient (in other words, to administer a placebo). The second strategy is to eliminate its non-specific effect, by hiding the administration of the active ingredient from the patients.

Unlike conventional clinical trials, in which the placebo effect creates observable improvements in patients who have unknowingly received a placebo, this second approach, the hidden administration of the active ingredient, works in roughly the opposite way. For example, if patients are already receiving an intravenous drip, they can easily be given an antipain medication without their knowing, and then asked to complete a questionnaire evaluating their subjective perception of their pain level. Next, they can be given exactly the same dose of the same medication openly (meaning that the doctor uses a syringe to inject the medication and explains its nature and expected effects to them), and then asked to complete the questionnaire again. If they report less pain this time, this indicates a non-specific component that is probably attributable to the placebo effect.

Such studies show that analgesic effects are far smaller with hidden administration, both of active medications and of placebos. For example, if a patient is told that he is going to be given an intravenous injection of a powerful analgesic that will ease his pain, and then a tourniquet is applied to his arm and he is injected with normal saline solution instead, he will experience pain relief. But that will not happen if he is already hooked up to an intravenous drip and is injected with the same dose of normal saline solution without being aware of it.

Another experiment has shown that the dose of analgesic needed to reduce pain by half was far higher with hidden administration, and that this held true for all four analgesics that were tested. The same trend was observed in the time lag before the analgesic effect set in: it took longer with hidden administration.

Experiments with open and hidden cessation of treatment with morphine confirmed these results: the pain returned more quickly and was more intense when the patients were told that their treatment was going to be halted than when it was halted without their knowing. This phenomenon can also come into play in the nocebo effect (see sidebar): in this case, the fear of the pain’s returning can aggravate the pain.

Exactly the same results were obtained in comparing open and hidden administration of the anxiolytic diazepam to patients who were experiencing major anxiety following an operation, as well as in comparing the open and hidden withdrawal of this treatment.

There are thus ways to study the placebo effect without even having to administer a placebo pill. A corollary is that a placebo pill delivered in such a way that the patient does not know about it will never have any effect on that patient. This is entirely understandable, because without a prior explanation of the treatment, the patient is in no position to build up any expectations about it. This is another reminder of the importance of the doctor-patient relationship among all the factors that contribute to the placebo effect.

The placebo effect is a special case of the brain’s more general ability to exert a profound influence on the functioning of the body. The discipline that examines this influence is called psychoneuro-immunology and developed out of research done by U.S. psychologist Robert Ader starting in the mid-1970s.

Ader fed laboratory rats a combination of sweetened water and an immunosuppressive drug and successfully conditioned them to associate the drug’s effects with the sweetened water, so that subsequently, just feeding them the sweetened water alone sufficed to lower their immune defences. This was the first scientific evidence that the nervous system can influence the immune system.

Since then, numerous experiments have confirmed that the two major adaptive systems of the human body—the brain and the immune system—are in constant communication with each other. They communicate through two main neural pathways: the hypothalamic-pituitary-adrenal axis and the sympathetic nervous system, as had previously been surmised by forerunners of psychoneuroimmunology such as Hans Selye and Henri Laborit.

It is interesting to consider the scientific view of the placebo effect in light of the evolution of this discipline. Before the 1970s, the potentially harmful effects of stress on health were still regarded as a fairly esoteric topic. Nowadays, psychoneuroimmunology is a very active research field, and no one in the scientific community any longer questions these interactions between mind and body. As a result, many researchers believe, the placebo effect is now reaching just about the same level of general acceptance.

Studies on the placebo effect are now providing increasing evidence that it involves cascades of biochemical reactions including, for example, the secretion of endorphins that can alleviate pain. Other forms of healing associated with the placebo effect might be due to a more general positive impact of expectations that help the immune system to function more effectively. Conversely, it has also been frequently confirmed that severe chronic stress can weaken the body’s immune functions and make it more vulnerable to a variety of pathologies, including cardiovascular disease and depression. Thus, a healthy immune system routinely eliminates the precancerous cells and viruses that are always present in the human body, while a depressed immune system allows them to proliferate.

This does not mean that, to oversimplify grossly, you can cure a cancer with a smile. But perhaps you can prevent some cancers by avoiding weakening your immune system. And as we now know, the thoughts and expectations generated by our brains can affect the neurochemistry of the complex mechanisms that keep us healthy.

Link : Neural top down control of physiologyLink : PsychoneuroimmunologyHistory : Father of PNI reflects on the field's growthResearcher : Robert AderLink : Expectations and associations that heal: Immunomodulatory placebo effects and its neurobiologyLink : Placebos and painkillers: is mind as real as matter?
Link : Book : La Solution intérieure. Vers une nouvelle médecine du corps et de l’espritLink : Peptides opioïdes,substances opiacées et réponse immunitaireLink : Les apports de la recherche expérimentale : le lien entre stress/détresse et pathologie organiqueResearcher : Anne HaringtonLink : Psychoneuroimmunology – Cross-talk between the immune and nervous systemsLink : Elaborate interactions between the immune and nervous systems

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