Placebo

CHAPTER 18 Placebo

When used as a noun, placebo means a treatment that lacks any specific therapeutic effect. In the case of a drug, a placebo would be an agent that lacks any pharmacological effect. In the case of a procedure, a placebo would be one that lacks any specific anatomical or physiological effect. Nevertheless, in other respects a placebo has all of the features of an intervention that should work.

When used as an adjective, placebo occurs in two forms: the placebo effect, and the placebo response. Placebo effect is the presumed or perceived effect that a placebo has on an individual. Placebo response is what the individual reports after having been administered a placebo, and is ostensibly due to the placebo effect.

Essentially, a placebo is not supposed to work. Any effect or response that it evokes is, therefore, paradoxical. The resultant paradox is difficult to handle in clinical practice. Consequently, placebo is a commonly misunderstood concept that is subject to abuse, misinterpretation, and myths.

PLACEBO RESPONDER

When patients exhibit a placebo response, practitioners and authors sometimes, if not often, refer to them as ‘placebo-responders.’ This term implies that the patient has an inherent trait that means that they will consistently respond to placebos. This is wrong.

There is no personality trait or psychological trait that causes individuals to respond consistently to placebos.¹ Experimental studies have shown that any individual at any time is liable to express a placebo response, depending on the circumstances; but also that such responses are not consistent.¹^–³ Indeed, one authority has ventured to conclude that proneness to placebo is universal.⁴

The placebo response is a variable phenomenon, and does not reflect anything about the individual who reports it. The term placebo responder, therefore, can have only a pejorative connotation, to dismiss or relegate patients for having exhibited a paradoxical phenomenon. When used, it expresses more about the prejudices of the practitioner than anything about the patient. Consequently, the term should be expunged from clinical vocabulary, and never used.

PLACEBO RESPONSES ARE FAKE

Some practitioners handle the paradox of placebo responses by dismissing them on the grounds that the patient has a psychological problem, is malingering, or is frankly lying. This is both a misinterpretation and misrepresentation of the placebo response.

The distinction is that a placebo response occurs after the intervention, ostensibly because of it. In contrast, malingering and lying require premeditation. To accuse a patient of malingering or lying, because they have a placebo response, is therefore tantamount to accusing them of premeditation. The placebo response provides no evidence of this. Such an interpretation, therefore, reflects the prejudices of the practitioner.

Nor is the placebo response a sign of psychological distress. Placebo responses occur under experimental conditions in individuals with no evidence of psychological disturbance.^5,⁶ Among patients with chronic pain, profiles of psychological distress do not differ between patients who have true-positive responses to placebo-controlled diagnostic blocks and those who have placebo responses,⁷ or between patients who have successful outcomes after treatment and those who do not.⁸

NOT IN CLINICAL PRACTICE

A common belief, though rarely enunciated, is that placebo responses occur only in research studies and, reciprocally, that they do not occur in ‘real’ practice. Implicitly, placebo responses are somehow precipitated only if and when patients enroll in controlled trials.

This is a self-serving belief, designed to excuse practitioners in the ‘real’ world of any responsibility to be alert to placebo responses, or to have their practices accountable to placebo effects. The belief conveniently ignores the realization that controlled trials are simply the means by which placebo responses can be demonstrated and quantified. That having been done, practitioners are warned to expect the same phenomenon, with the same prevalence, in conventional practice. Practitioners choose to ignore this warning. They prefer, instead, to believe that all positive therapeutic effects of their practice must be due to the specific effects of their ministrations, and that their successes could not be due to something as ephemeral as a placebo effect. Under these conditions, ignoring the prevalence of placebo effects serves to protect the ego of a practitioner, while offending scientific accountability to the truth.

CONSTANT RATE

A widespread urban myth is that about one-third of patients in any cohort will express a placebo response, implying some sort of endemic influence. This myth has been traced to an early study of placebo responses.^1,³ In reviewing the literature, Beecher⁹ encountered a wide variety of placebo response rates, ranging from 15% to 58%. A figure of 35.2% arose as a numerical average of these rates, unweighted for sample sizes. Subsequent studies have encountered placebo response rates from as low as 0% to as high as 100%.¹ There is nothing constant about 35%. Placebo response rates differ considerably according to the circumstances of the study.

MECHANISM

In the context of pain medicine, a placebo would be an agent or a procedure that should have no effect on pain by pharmacological, anatomical, or conventional physiological means. A placebo response would be relief of pain despite this lack of a conventional means by which the pain could be relieved. The occurrence of a placebo response implies a placebo effect.

The mechanism or mechanisms of that placebo effect remain largely elusive. Theories have been proposed; but, of late, experimental studies have pursued its physiological basis.

The fact that pain is relieved implies that whatever the mechanism is of placebo effects, it must involve the nociceptive system. The prevailing theories about placebo invoke some sort of suppression at one level or another of the nociceptive system.

Conditioning

Conditioning is a prominent theory amongst psychologists who seek to explain the placebo effect.^2,³ The theory is based largely on data from experimental studies, in which subjects previously exposed to an intervention have continued to express positive responses when that intervention was surreptitiously or progressively replaced with a sham intervention.

However, it is hard to reconcile this theory with the nature of interventional spine medicine. If anything, patients are likely to encounter repeated failures of treatment and, therefore, would be conditioned not to respond. Indeed, the conditioning theory has been adapted to fit this phenomenon by becoming an explanation for nocebo responses or ‘placebo sag.’² In contrast, if the contention is that patients expect relief when they consult a doctor, instead of conditioning theory, expectation is a more appealing explanation.

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Tags: Interventional Spine An Algorithmic Approach

Sep 8, 2016 | Posted by admin in PHYSICAL MEDICINE & REHABILITATION | Comments Off

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