L17 Flashcards
What is the placebo effect?
A psychobiological event attributable to the overall therapeutic context in which a treatment is given. It is a beneficial effect produced by a placebo treatment, which cannot be attributed to the properties of the placebo itself, and must therefore be due to the patient’s belief in that treatment.
List some peripheral effects of placebo treatment
Increased hormone secretion, cytokine levels, lymphocyte activation
*Mechanisms largely unknown
Mechanisms of the placebo effect:
- Expectations
- Behavioural conditioning: believing you are getting better so do other things to make yourself feel better e.g. exercise
- Quality of patient-physician relationship
Do interaction with genetic factors play a role in placebo effect?
Yes - placebos in treatment of parkinson’s disease cause increased endogenous striatal dopamine which is greater in individuals with a particular polymorphism in a gene that modulates aminergic tone (tryptophan hydroxylase 2)
Do you need to be conscious for placebo effects?
Not for all placebo effects - not for conditioned ones where you have habitual association with certain outcomes for certain contexts
Only need to be conscious for the expectation/belief mechanisms
Do rats exhibit placebo effects?
Not sure
What do we know about placebo that can be exploited to control pain?
- It is antagonizable by opiate antagonists
- Spinal cord nociceptive activity reduced
- PFC and Cingulate and PAG increased activity
- Size of effect to be related to being “reward oriented” (it has to do with positive expectations - people who are positive respond better to placebo effect)
During placebo study - there is increased activity of DLPFC and OFC which correlate with an increase in?
Midbrain (esp. PAG where opiate neurons are)
Physiological changes with effective placebo treatment
- Activation of descending pain modulatory network
- Decreased activity in somatosensory areas
- Changes in brain neurochemistry esp. the endogenous opioids
When doesn’t the placebo effect work?
When you don’t have the capacity to generate belief states about the quality of care you are getting e.g. people with Alzheimer’s disease
Rats can be conditioned to associate a neural stimulus with either a weak or strong nociceptive stimulus
People can be conditioned to experience pain relief on neutral faces in this study
Rats can be conditioned to associate a neural stimulus with either a weak or strong nociceptive stimulus
People can be conditioned to experience pain relief on neutral faces in this study
Do you want to have placebo effects when designing drug treatment/therapy?
No - so you know the drugs effect alone
It is not relying on info coming from the periphery and then being built up. It is an example of top down processing - what is the top?
We know what the end result is. We want to change it by modulating the top of the hierarchy: the PFC and its currency, metaphor and abstraction - imagination
