Week 11- Placebos Flashcards
Placebo analgesic response;
a process by which “the mere belief that one is receiving an effective analgesic [pain relief] treatment can reduce pain” (Wager et al., 2005, p. 1162)
Placebo analgesic responses appear to be mediated by endogenous opioid pathways (endorphin release). Placebos activate endogenous opioid pathways, which affect:
painperceptionareasinthebrainsuchastheprefrontalcortex (PFC), insula, anterior cingulate cortex (ACC), and orbitofrontal cortex (OFC) (dampening subjective appraisal of pain)
descendingpainfibrestoinhibitpain(dampeningsensationthat comes up from the spinal cord by closing the ‘gate’)
Caveats and complexities of Placebos - Visual Input
Stronger if people see the drug administered. As shown in the figure below, pain reduction is greater when seeing pain relievers being injected (‘open’) versus not seeing pain relievers being injected (‘hidden’).
Benedetti 2021; Placebos and Movies; What do they have in common? Reading Summary
- Benedetti argues that placebo effects are like emotional and physiological responses to movies - they reflect fictitious treatments that simulate reality
- Placebo effects are common phenomena that tie in with expeirences in everyday life, like watching movies and they activate corresponding physchobiological mechanisms in the brain even though we know the movies aren’t real
So deception is not necessary for evoking placebo effects
This is also consistent to how patients are sensitive to healing contexts - eg. feel better after seeng a doctor
Fuente-Fernandez et al., 2001 Parkinsons and Placebos
Paul a Parkinsons patient was taken off of his Parkinsons treatment to take part in a study. In this study he was given a placebo pill which was hugely effective.
In a brian scan whilst on the placebo, it showed there was reduced activity in the striatum explained by an increase in dopaminergic activity or release from the Nucleus Accumbens (which would increase the handbrake on unwanted motor activity). This sort of response is what you’d expect to see on a neurobiological level as if he’d been taking the active drug
Benedetti 1996 - Naxolone Study
Published a key study showing that Naloxone blocks placebo-induced pain relief (analgesia).
Participants were connected to an IV drip bag and told they’d be subjected to a pain task.
- in stage 1; researchers showed that placebo induced analgesia ocurs
Thyey did this by during the pain task given a hidden dose of saline (no analgesic effect and no particiapnt awareness) or an open dose of saline (no analgesic effect but particiapnt awareness) and they found the open saline injection resulted in a placebo effect with a blunting of pain perception
In stage 2; researchers wanted to show that Naloxone disrupts the normal timecourse of placebo-induced analgesia
They did this by giving an open injection of saline to all participants to act as a placebo. Then for half the participants mid-way through the pain test, they gave hidden dose of Naloxone which blocked endogenous opioids (analgesics) and researchers found these participants reported the placebo wearing off and experiencing greater pain
This showed that placebo analgesic responses are mediated by activation of the body’s endogenous opiate system in the brain and periphery; and this can be blocked by Naloxone
Summary of Acupuncture
There is evidence that acupuncture involving non- specific insertion of needles may be equally effective as specific point acupuncture for pain relief.
Not inserting the needle (using sham needles) may also have beneficial effects but not as strong as actually inserting a needle into the body.
Therefore, acupuncture works to reduce pain but possibly not likely through pathways originally thought (meridians).
Define complementary and Altnerative Medicine (CAM)
Treatments to cure illness and improve health and well-being that are outside of the standard western medicalized approaches.
Closing the Pain Gate
- There are descending analgesic nerves (from brain to spinal cord) with receptors that match:
Exogenous opiates (opium, codeine, morphine, heroin etc.)
Endorphins (“nature’s painkiller”)
When opiates or endorphins are ingested or activated, they inhibit ascending pain signals by closing the gate from the spinal cord to the brain (by activating the inhibitory interneuron)
What causes the release of endorphins?
exercise (10 minutes minimum); acute stress; childbirth and surgery; acupuncture; placebos (Sapolsky, 2004, ch. 9)
Prof Tor Wager and his work on Placebo Analgesic Effects
Aims: to clarify the brain mechanisms for how placebos influence pain (the pain placebo analgesic response) by asking where along a sensation-to-reporting continuum placebo effects occur, with three options:
Option 3: Placebos change what we verbally report not what we feel (e.g., we feel an ‘8’ level pain, but only say it’s a ‘4’ level pain to please the experimenter, known as “demand characteristics”).
Option 2: Placebos change what we feel by influencing the interpretation of sensory signals via expectancies (PFC) and appraisal (OFC, Insula, ACC).
Option 1: Placebos change what we feel by influencing actual sensory signals via changes to somatosensory signals from periphery (gate control), brainstem (PAG), or somatosensory cortex (S1, S2).
His work ruled out option 3 - but suggested option 1 and 2 stand true
Summary of Placebo Analgesics
- Placebo analgesic responses are mediated by activation of the bodys endogenous opiate system in the brain and peripery; activation of the endogenous opiate system probably accounts for why acupuncture reduces pain
- Some researchers like Wager (2005) use imaging research to show how placebos change brain areas associated with expectancy and appriasal as well as dampen sensation
- Other researchers like Sapolsky (2004) and Benedetti (1996) focus on how placebos activate endogenous opioids, which can inhibit pain signals from the spinal cord. This is demonstrated in Benedetti (1996) who found that naloxone blocks the placebo effect by blocking activation of endoenous opioids
How do placebo analgesics dampen sensory signals coming from the periphery?
Placebos activate endogenous opioids, which activate descending analgesic nerves, which inhibit ascending pain signals by closing the gate from the spinal cord to the brain (by activating the inhibitory interneuron).
If we block these descending analgesic nerves, we can block placebo effects!
Two questions we ask when assessing the validity or suitability of CAM methods
What is the empirical evidence for acupuncture’s effectiveness?
What are the proposed mechanism(s) for any effects?
Acupuncturedefined
= Process by which small needles (about the thickness of 1-2 hairs) are inserted into special points along the body to stimulate and rebalance the flow of chi, the “life energy” that flows through channels in the body called meridians.
Illness as imbalance in ch’i—excess or deficiency
Acupuncture points exist all long these meridian lines and allow contact with the ch’i; different points correspond with imbalances in different organs
Iving Kirsch ; Hypnotic Placebos
Placbos and Hypnosis have three things in common; belief, expectation and suggestion
- he used hypnosis on a dental patient who got his wisdom tooth removed without any pain killers (it was gross I hope you didn’t watch the video)
Other types of placebos
Not all placebos work through influencing endogenous opiates, however. For example, placebos have been shown to induce the release of dopamine in the striatum, which is a treatment used in Parkinson’s disease or, placebos can induce other chemical changes in the body, including mimicking the effects of oxygen.
