placebo and expectancy

8/11/2019 Placebo and Expectancy

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Mind Over Matter:

Placebos and Expectancies


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Quiz!1. T/F: Placebos make patients feel

better; they dont actually get

better

2. T/F: There are no negative effects

of placebos

3. T/F: Placebos can reduce asthma

and make wounds heal faster

4. T/F: Placebo therapy could be the

end of biomedicine as we know it

5. T/F: Doctors can lie to patients if it

is in the patients best interest.


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Placebo

From Latin placere - to please or I will please

Placebo

an innocuous substance without a specific physiological effect

Clearly active and not innocuous; has physiological effects

any treatment devoid of specific actions on the patients

symptoms or diseases that, somehow, can cause an effect upon

the patient. Obviously have specific actions but true that we dont know precisely

how


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The Placebo Effect

Based on expectancies "anticipation of a systematic if/then relationship between events and

objects." (Tolman, 1932)

Afflictions that have strong psychological components

(pain, anxiety, and depression) tend to show high rates of

placebo effects

~ 65% of patients in antidepressant trials get better with drug

~ 35% of patients in antidepressant trials get better with placebo

Many times these rates dont differ statistically (30% rule)

A meta-analysis showed that antidepressants relied onthe placebo effect for 75% of their effectiveness

The remaining 25% real drug effect may be a disguised

placebo effect


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Placebo Effect

If expectation of pain can increase pain intensity,

how might expectation of pain reduction influence

perception?

Experimental results

85% of Ss given placebo for relief of pain caused byHerpes (cold sores or genital sores) reported pain

reduction

56% of patients given sham treatment (small skin

incision) for angina (heart pain) reported significantpain reduction

On average, 33% of Ss in placebo pain studies report

pain reduction


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Are many drug effects simply placebo

effects?

Placebo effects were discovered in the 1950s

Administering a simple sugar pill or water alleviated symptoms or

even cured some diseases

However, its a minority view that its all placebo

Nonetheless, some placebo effects may be present in all

drug effects

How do you dissociate placebo from other effects?


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Nocebo (I will harm)

(Walter Kennedy, 1961)

A nocebo responseoccurs when a drug-trial's subject'ssymptoms are worsenedby the administration ofa placebo.

If the patient believes asubstance is harmful itcan cause negative

effects.


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Nocebo Effect

Approximately of patients receiving a placebo

voluntarily report adverse side effects

When prompted, between 27% and 71% report

adverse side effects Usually general complaints (difficulty

concentrating, nausea, fatigue)


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Note that if the nocebo effect is greater than thetherapeutic gain and the natural history of thedisease, the treatment will make the patientworse.

The evil eyevoodoowitchcraft


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Dealing with Placebo and Nocebo Effects

in ExperimentsStudy Designs

(randomly assigned to experimental/placebo arms; passive vs activeplacebos)

Blinded Study- Participant doesnt know if they are receivingtreatment or placebo

Double-Blinded Study- Participant and Experimenter do not knowif treatment or placebo is being given

Double-Blind, Crossover Study- Same as double-blinded, exceptparticipants get treatment and placebo in random order (controlsfor Ss variability)


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Wh th hi h i t


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Why the high responsiveness to

expectation of pain relief?

Evidence that expectation of pain relief activates mu-opioid neurotransmitter system (endorphins)

Zubieta et al - Placebo Effects Mediated by Endogenous Opioid Activity on -Opioid Receptors (2005)

Red & orange

indicate regions ofheightened mu-

opioid activity

when P reports

positive effect ofplacebo


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Other factors involved in the placebo effect

(cont)

Natural disease progression may be cyclical

gets worse then gets better

Enrolling in a clinical trial or seeing a doctor gives some

individuals a greater sense of control over the illness

Feelings of concern and caring from nurses, doctors, and

researchers

A healing environment

Difficult to measure some illnesses/diseases

Scales for measuring pain/anxiety/depression are not clear cut

and tend to be somewhat labile

Poor patient selection (no test for susceptibility to

placebo)


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Cognitive Explanations: Schemata

Organized representations of conceptually-relatedinformation that guide processing of new information

Facilitate memory and comprehension

Influence the speed of information processing and problemsolving

Gather information into meaningful and more easily retrievedunits

Enable the individual to fill in missing information

Provide greater confidence in prediction and decision making.


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Alcohol Expectancies (cont)

With age and drinking, alcohol

expectancies have more to do

with arousal/sedation than

whether alcohol is good or bad

placebo and expectancy

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