Placebo Effects September, 20, 2012
- Pain lecture: on Midterm 1
- Power of Suggestion video
- About 30% of people will experience relief from placebo.
- Endogenous pathways: systems built in the body that modulates pain. Placebo
allows these systems to become active to handle pain.
- A lot of the relief that patients experienced was due to placebo (endogenous,
biological, and physiological).
What is a Placebo?
- Acupuncture needles: some individuals are scammed (“sham” treatment”)
because the needles don’t actually go into the skin.
- Past experience with a drug (you take a Tylenol every time you get a headache –
- Method of triggering an endogenous effect.
- Side effects, self-reinforcing effect (on the lookout for evidence, confirming
evidence when taking the drug).
In clinical trials
- Actual drug vs. starch drug (ex. acupuncture vs. sham)
- 50% drug, 50% placebo
- Regression toward mean: if you are feeling bad one day, statistically you’ll be
feeling better the second day.
In placebo effect studies
- Placebo pill vs. waitlist
- People on waitlist will get better due to passage of time.
How stuff works: Placebo video
- Drug must beat placebo in 2 trials to be approved by FDA
- When valium is tested in France, it out performs the placebo but in the US the
placebo outperforms valium.
- Drug companies are finding it hard to beat the placebo.
- Meta-analysis (pool many studies together): antidepressants are no better than
placebo (starch/sugar pills)
History of Placebo Effect
- Treading soldiers who had been badly injured
- 38% vs. 83%
- For the soldiers the wound meant that they were going to survive and go home,
the wounds meant freedom. For civilians the wound meant that they couldn’t do the things they wanted
to, the wound had no redeeming value for them (they felt crippled).
- “Just a placebo effect”.
- Loss of oxygen to heart (1994) – myocardial ischemia
- 1972: both pills has nothing but starch
- Analgesics: aspirin (just knowing that you have the branded medicine provided
relief). Chemically the same: unbranded & branded medicine.
- Fillers: pharmacologically inert.
Why/how do Placebo effects occur?
- Expectations: that both patients and clinicians have.
- Placebos by injection are more effective.
- Expectations cause systems to start working in the brain that regulate pain.
- Anxiety boosts pain; anything that can reduce anxiety (expectation) can reduce
- Two very different messages but the experience was the same. (Staats. 1998)
- Threshold of pain: when pain starts while hand is in water.
- Tolerance: when they draw their hand cause they can’t take it
When they received positive message, they could tolerate more pain
Pre: Before they received the message.
- Thoracotomy: open up stomach (serious surgery, a lot of pain).
Natural: given the drug but not told (requested 11.5 mg)
Uncertainty: they got the real drug but told that they might get drug
or placebo. (Requested: 9.2 mg).
Deceptive: told that they were getting drug, telling patient that
they are getting a potent pain killer effect how much they
- Supposedly 3 different analgesics.
- Then implemented conditioning protocol.
Applied heat in varying temperatures