psyc 372 placebo

what is placebo effect

measurable improvement due to belief in treatment rather than actual pharmacological action

who first studied the placebo effect

Henry Beecher during WWII, injected soldiers with saline instead of morphine and saw pain relief

what psychological factor plays a role in placebo effects

expectancy; believing treatment will work activates physiological changes

how does classical conditioning explain placebo

body learns to associate “treatment” with feeling better, producing similar effects even when treatment is absent

what physical traits make placebo more effective

bigger, brighter, bitter-tasting 

what did Espay discover in placebo’s in parkinsons patients

“expensive” placebo produced stronger improvements than the “cheap” one

what did Zubieta find about placebo and pain

placebo activated brain mu-opioid system in pain-processing regions, reducing pain

how did sauro show natural opioids are involved in placebo pain relief

injecting naloxone (opioid blocker) reversed placebo’s pain relief

what did fuente-fernandez discover about placebo in parkinson’s

placebo triggered by dopamine release in striatum, improving symptoms

what gene is linked to strong placebo anxiety in furmark

the long allele of 5-HTTLRP and the G variant of THP2 G-703T (serotonin related genes) 

what percent of physicians admit to using placebo in practice

45-60%

why do some doctors use placebo

calm patients, satisfy requests for unnecessary medication, “mollify” complaints

what is AMA’s official stance on placebo

use with patient knowledge & consent; deception undermines trust

what is “active placebo”

a placebo that mimics side effects without providing therapeutic benefit

what study design best controls placebo effect

double-blind studies, neither participants or researchers know who gets the real drug

kirsh & sapirstein, what percentage of antidepressant response is placebo

50% placebo, 27% drug, 23% unidentified factors

what did reif conclude about placebo in antidepressant trials

placebo account for 68% of drug effects; clinical practice should harness not ignore placebo

what is “nocebo effect”

negative expectations causes worse symptoms or side effects

what brain regions are involved in placebo effect

prefrontal cortex, anterior cingulate cortex, nucleus accumbens, amygdala

which neurotransmitter systems are linked to placebo

opioid, dopamine, endocannabiniod, serotonin

why do placebo response vary

genetics, expectation levels, personality, culture

how does culture influence placebo

different cultures view side effects & healing different 

overall lesson from placebo research

belief & context can shape physiological and psychological health outcomes