Chapter 14: The Neurobiology of Placebo Analgesic Effects

placebo

an inert substance or treatment, effects depend upon the activation of endogenous systems and brain networks and influence behaviors and ultimately clinical outcomes

placebo effect

the mind’s belief that we are receiving a treatment (even when in actuality we are not receiving an active one) can trigger a cascade of events that change pain symptoms’ perception and healing process

our expectancies can “influence” the way the body responds to treatment and anticipates

covert-overt paradigm

a protocol wherein researchers can examine the effects of a drug when patients are informed about its effects (overt) or when it is given in a hidden way (covert) of drug administration

how does the placebo effect reduce pain?

reduces pain because of series of physiological mechanisms that influence how pain is processes, perceived, and decoded at the level of central and peripheral nervous systems

functional MRI

researchers have used this techniques to explore the activity occurring in the brain in response to events such as painful stimuli given in the presence of a placebo

it detected changes linked to blood flow

what brain changes have been associated with the placebo effect?

reduced activity in the brain areas such as the thalamus, somatosensory cortex, ACC, and insula

dorsolateral PFC

has been associated with increased brain activity related to expectation of pain relief and placebo effects, as well as maintenance of placebo effects

nocebo

a negative expectation of treatment

what alters placebo and nocebo effects?

violation of expectations alters this, expectancy violation is associated with a reduction of the effect size for both placebo and nocebo effects and with an extinction of placebo effects

effect size

in statistics, the measurement of the magnitude of a difference between two groups or outcomes

behavioral placebo analgesia

were correlated with activity decreases in these networks, and the thalamus, habenula, mid-cingulate, and supplementary motor area

naloxone (mu opioid receptor antagonists)

eliminated placebo-induced pain relief suggesting a potential role of the endogenous pain modulatory systems in placebo analgesia

endorphins

endogenous forms are released when people expect to feel better

there was an activation of the endogenous opioid system as a result of the exposure to an exogenous opioid treatment resulting in an increase of pain endurance

in an experimental setting, scientists asked study participants to endure a painful procedure with and without substance given after mophine produced an increase of pain endurance as compared to the no-treatment group. This effect was blocked by naloxone. This finding suggests that:

the inert substance triggers release of vasopressin

there was an activation of the endogenous opioid system as a result of the exposure to an exogenous opioid treatment resulting in an increase of pain endurance

the naloxone binds the opioid receptors facilitating an activation of the descending pain modulating system

the increase of pain endurance following the administration of an inert substance is merely a bias without biological substrates

vassopressin

induce conciliatory behaviors as well as interpersonal communication, favoring “tend-and-befriend” behavioral patterns of women toward other women, and in me “fight-or-flight” toward other men

involved in placebo response in women, but not in men

The OPRM1 rs1799971 by COMT rs4680 by FAAH rs324420 interaction explains at least in part the variability in distinct profiles of placebo analgesic effects.

genetics influence placebo effects. Which of the following is true?

The OPRM1 rs1799971 by COMT rs4680 by FAAH rs324420 interaction explains at least in part the variability in distinct profiles of placebo analgesic effects.

One single SNP can predict well placebo effects.

Genetics cannot predict placebo effects

Twins studies are not needed to discover why placebo effects occur.

animal research

not used a lot in placebo research due to animals inability to use language or to communicate how much pain they are experiencing

dose-extending placebos

subtherapeutic or sham treatments that can be interspersed with active treatments in accordance with reinforcement learning principles to induce placebo effects while mimicking the action of the active drug and reducing the overall intake

number needed to treat (NNT)

in relation to drugs, this refers to the number of people who need to receive the treatment before you see a benefit, or prevent a negative outcome

Placebo effects in orofacial pain patients are larger in Whites than AA/Black participants

which of the following is true of placebo effects in orofacial pain patients?

Placebo effects in orofacial pain patients are larger than healthy participants.

Placebo effects in orofacial pain patients are not influenced by racial differences.

Placebo effects in orofacial pain patients are larger in Whites than AA/Black participants

Placebo effects in orofacial pain patients are not related to the race of the experimenter indicating no racial influences.