Placebo

Question 1

How many conditions does placebo effect

Answer 1

60-90% of conditions

Benson 1996

Question 2

Review of measurable placebo effect

Answer 2

McQuay 1996
Pain reduction by 50%
3-37% in placebo
5-63% in treatment

Question 3

Mechanisms of placebo

Answer 3

Psych - classical conditioning, outcome expectancies

Neuro - opioid, non-opioid

Question 4

Classical Conditioning

Answer 4

Repeated association between neural stimulus and treatment

Difficult to exclude outcome expectancies

Question 5

Outcome Expectancies

Answer 5

Expectation of future responses

Question 6

Opiod mechanisms

Answer 6

Pain related effects reduced/stopped with opioid antagonists

Question 7

Non-opioid mechansims

Answer 7

Placebo altered dopamine levels in patients with parkinson’s disease

Question 8

Non-disguised placebo

Answer 8

Can still show positive effect
e.g. IBS trial, “placebo pill” vs same standard of care
Greater improvement (P=0.002)
Kaptchuk 2010

Question 9

Three arm trials

Answer 9

Account for regression to mean and spontaneous remission e.g. waiting list

Question 10

Harnessing placebo

Answer 10

Positive expectancies
- deliberate and specific suggestion of likely positives
Negative expectancies
- deliberate minimisation of potential negatives

Question 11

Evidence for positive expectancies

Answer 11

Rutherford 2014
Patient expecations seen to have negative effect (possibility of changing from antidepressant to placebo saw reduced effect)