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Placebo effects. Placebo is Latin for “I will please” Refers to any type of treatment that is inert Used in research trials to objectively test the efficacy of new treatments One group is given the treatment, while another group (the control group) receives a placebo

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placebo effects
Placebo effects
  • Placebo is Latin for “I will please”
  • Refers to any type of treatment that is inert
  • Used in research trials to objectively test the efficacy of new treatments
  • One group is given the treatment, while another group (the control group) receives a placebo
  • Comparing the results from both groups should reveal the effects of the treatment
placebo american heritage dictionary
Placebo American Heritage Dictionary
  • A substance containing no medication and prescribed or given to reinforce a patient's expectation to get well
  • An inactive substance or preparation used as a control in an experiment or test to determine the effectiveness of a medicinal drug
  • Something of no intrinsic remedial value that is used to appease or reassure another
placebo effects cont
Placebo effects (cont.)
  • Interestingly, some people get better in the placebo group
  • This phenomenon is known as “the placebo effect”
  • The placebo effect is substantial
    • About one third of people taking placebos for a number of complaints will experience relief
  • The underlying mechanisms remain a mystery
  • The term “sham treatment” is often used instead of placebo
  • Definition:
    • Something false or empty that is purported to be genuine; a spurious imitation
placebo effects cont5
Placebo effects (cont.)
  • The placebo effect is triggered by the patient's belief in the treatment and their expectation of feeling better
  • If symptoms are relieved by taking an inert substance or undergoing a dummy procedure, was the original illness imaginary?
  • No
factors that influence the placebo effect
Factors that influence the placebo effect
  • Characteristics of the placebo
    • If the pill (or treatment) looks genuine, the person taking it is more likely to believe that it contains active ingredients
    • Larger sized pills suggest a stronger dose than smaller pills, and taking two pills appears more potent than just one
    • Injections have a more powerful effect than pills
factors that influence cont
Factors that influence (cont.)
  • Attitude of the patient
    • If the person expects the treatment to work, the chances of a placebo effect are higher
    • However, the placebo effect may still take place even if the person is skeptical of success
    • The power of suggestion is probably at work here
factors that influence cont8
Factors that influence (cont.)
  • Doctor-patient relationship
    • If the person trusts their health care practitioner, they are more likely to believe that the placebo will work
    • Chiropractors typically instill more trust in their patients, consequently critics have pointed to this as a likely explanation of our successes
placebo effects cont9
Placebo effects (cont.)
  • Types of placebos
    • Pills are well-known for their placebo effect
    • However, a placebo can be any inert or “dummy” treatment
    • Special diets, exercise, physical therapy or surgery
    • Even chiropractic manipulation

Psychic surgery -

Is actually produced by sleight of hand

Animal tissue and blood are used to give a realistic appearance, while a patient's fleshy midriff helps create the

illusion that the surgeon's fingers have actually penetrated the body

Still practiced today in Brazil and the


how placebos work
How placebos work
  • Self-limiting disorders
    • Many conditions are self-limiting (e.g., common cold, some back or neck pain)
    • They will resolve on their own with or without treatment
    • Symptoms resolving is merely coincidence
how placebos work cont
How placebos work (cont.)
  • Remission
    • The symptoms of some disorders, such as multiple sclerosis and lupus, may wax and wane
    • A remission during a course of placebos may be coincidence, and not due to the placebos at all
how placebos work cont13
How placebos work (cont.)
  • Changes in behavior
    • The placebo may increase a person’s motivation to take better care of themselves, which may be responsible for the easing of their symptoms
  • Altered perception
    • The person’s interpretation of their symptoms may change with the expectation of feeling better. (e.g., a sharp pain being reinterpreted as an uncomfortable tingling)
how placebos work cont14
How placebos work (cont.)
  • Reduced anxiety
    • Taking the placebo and expecting to feel better may soothe the autonomic nervous system reducing levels of stress chemicals
  • Brain chemicals
    • Placebos may trigger the brain to release endorphins, the body's own natural painkillers
how placebos work cont15
How placebos work (cont.)
  • Altered brain state
    • Research has shown that the brain responds to an imagined scene in much the same way it responds to an actual visualized scene. Placebos may help the brain to remember a time before the onset of symptoms, and then bring about physiological change
    • The so-called “remembered wellness” theory
placebo examples
Placebo examples
  • A meta-analysis of studies of depressed individuals taking antidepressant medications suggests that approximately:
    • One quarter of the drug response is due to the administration of an active medication
    • One half is a placebo effect
    • The remaining quarter is due to other nonspecific factors
  • Listening to Prozac but Hearing Placebo: A Meta-Analysis of Antidepressant Medication. Prevention & Treatment, Volume 1, Article 0002a, June 26, 1998
placebo examples cont
Placebo examples (cont.)
  • In a survey of surgery for lumbar disc disease, although no disc herniation was present in 346 patients (negative surgical exploration), complete relief of sciatica occurred in 37 percent and from back pain in 43 percent
placebo examples cont18
Placebo examples (cont.)
  • Moseley et al did a double-blinded, randomized, placebo-controlled trial to compare arthroscopic lavage and debridement vs. a sham procedure
  • They found that all three treatment groups fared equally: subjective symptomatic relief was reported, but no objective improvement in function in any of the groups
placebo examples cont19
Placebo examples (cont.)
  • Forty years ago, a young Seattle cardiologist named Leonard Cobb conducted a unique trial of a procedure then commonly used for angina, in which doctors made small incisions in the chest and tied knots in two arteries to try to increase blood flow to the heart. It was a popular technique and 90 percent of patients reported that it helped, but when Cobb compared it with placebo surgery in which he made incisions but did not tie off the arteries, the sham operations proved just as successful. The procedure, known as internal mammary ligation, was soon abandoned
    • "The Placebo Prescription" by Margaret Talbot, New York Times Magazine, January 9, 2000
sham v pill
Sham v. Pill
  • Kaptchuk et al. Sham device v inert pill: randomised controlled trial of two placebo treatments. BMJ  2006;332:391-397.
    • Fake acupuncture and sugar pills were tested for their effect on relieving arm pain
    • Both groups noticed improvements, but fake acupuncture was significantly better
    • 25% of acupuncture group noticed side effects and 3 of the sugar pill group actually withdrew because of them

Waiting list, where Hawthorne effects, natural progression of the

disease, and regression to the mean could be observed

“Limited” interaction that involved placebo treatment plus

minimal patient-practitioner interaction

“Augmented” interaction that also involved a placebo treatment,

plus a defined positive patient-practitioner relationship.

Kaptchuk T. Components of placebo effect: randomised controlled trial in patients

with irritable bowel syndrome. BMJ. 2008 May 3;336

natural history of a disease vs placebo effect
Natural history of a disease vs. placebo effect
  • The body has a natural ability to heal itself and people heal spontaneously, occasionally even when the illness is serious
  • Hard to differentiate from placebo effect
  • Cases of spontaneous remission sometimes end up being regarded as miracles
why is this important
Why is this important?
  • Placebo effects, disease natural history, and regression to the mean can result in high rates of good outcomes, which may be falsely ascribed to specific treatment effects
  • The true causes of improvements in pain after treatment remain unknown in the absence of independently evaluated randomized controlled trials