Placebo Effects Flashcards
What is a complimentary therapy?
- A heterogeneous group of therapies that share a focus on, or integration of, treatment of mind and spirit as well as body (Franck et al., 2007)
- Often focus on symptom relief or prevention rather than cure
Give 2 examples of complementary therapies
- Accupuncture
- Aromatherapy
- Cupping
- Herbal Medicine
- Yoga
- Reiki
Complementary therapies are much less researched than mainstream medicine. Does absence of evidence indicate evidence of absence?
- What if complementary therapies show no clinical effects but improve wellbeing.
- i.e. Physical Activity for treatment of depression vs obesity! Evidence base varies hugely.
- Should still be used by indivdual if not doing physical harm, and they are gaining benefit from it in anyway
Why are complementary therapies not widely offered on the NHS
- Can help relieve pain/discomfort
- But limited resources/funding from the NHS- other services more important to fund
- Evidence base weak!
- Available privately
Define a placebo
- Treatment effects of remedies that are not understood to have any direct link to the outcome.
- Placebo effects mimic drug effects (e.g. pain relief).
- Can also mimic drug side effects (e.g. nausea) – nocebo.
- Placebo effects can be very powerful!
Describe the 1996 McQuay systematic review on placebos
- Five placebo-controlled RCTs
- Acute postoperative pain (130 out of 525 had placebo).
- Pain relief measured on scale of 0 to 100%.
- 7% to 37% experienced at least 50% pain relief in the placebo arm (clinical effect)
- 5% to 63% experienced at least 50% pain relief in the treatment arms (still works better)
Define the Van Laarhoven (2015) Systematic review
- 34 trials of chronic itch (due to atopic dermatitis or psoriasis).
- Placebo treatment significantly decreased itch (1.3 out of 10, 95% confidence interval 1.02–1.61) compared with baseline itch (effect size 0.55).
- Placebo effects have a considerable role in these patients’ treatment.
Is the placebo effect;
- Physiological
- Psychological
- Both
Both!
Describe the Finnis 2010 Outcome expectancy psychological mechanism of placebos
- Patients given placebo have expectations of future responses.
- Can be manipulated with verbal cues e.g. by stating whether a treatment is likely to reduce pain.
- Mediates effects in experimental and clinical pain, motor performance in Parkinson’s disease, changes in emotions, and brain responses in patients with drug addiction.
- Placebo effects can be stronger depending on the mode of delivery i.e. IV/Injection/Surgery/Tablets
Describe the Finnis 2010 classical conditioning psychological mechanism for placebo effects
- Repeated associations between neutral stimulus and an active drug (unconditioned stimulus).
- Neutral stimulus elicits response characteristic of the unconditioned stimulus.
- Has been demonstrated in both animal and human studies but difficult to exclude any cognitive component (such as expectation) in human beings.
- More an unconditioned stimulus is paired with a conditioned stimulus, you create a pairing for an outcome i.e. pain reduction.
Describe the neurobiological mechanism involved with the opioid receptors in a placebo effect
- Most research has addressed placebo analgesia.
- Pain related placebo effects can be completely or partly reversed by the opioid antagonist naloxone.
- Confirmed with brain imaging techniques such as PET & fMRI.
- In one PET study, brain changes in response to placebo were reported to be similar to changes seen after with opioid drug.
Describe this:
The middle scan shows there is a neurobiochemical response to placebo treatment, although its not as pronounced as the opioid treatment
Describe non-opioid responses to placebos
- Different placebo mechanisms can be produced depending on the drug used in the conditioning protocol.
- Placebos been shown to change dopamine release in the striatum, basal ganglia and thalamus in patients with Parkinson’s disease.
- Changes in metabolic activity in the brain after administration of placebo in patients with depression.
Out of placebo aspirin and oxygen mask, which showed a larger improvement on a hypoxic high-altitude headache
Larger effect exerted from the oxygen mask- even with placebo the physiological mechanisms were still different.
This means its working at a higher level than just psychological/neurobiological.
What biochemical change was observed with placebo aspirin- hypoxic headache
inhibition of cyclo-oxygenase
What biochemical change was observed with placebo oxygen mask- hypoxic headache
- reduced ventilation
- reduced blood alkalosis
Describe what is being observed here
Different mechanisms of placebo link to outcomes.
Conscious expectations can lead to lots of effects which equals a placebo effect being experienced.
Very much effected by the way in which its manipulated i.e. mode of delivery or how we’ve learnt that effect
Why do placebo effects need to be controlled for in clinical trials?
- When placebo effects are large they cast doubt on the intervention efficacy and on the proposed mechanism of action of the “real” treatment.
- Is the effect partially or wholly due to psychological – rather than pharmacological processes?
- Systematic review of 115 studies found no significant difference between treatment and placebo effects (MD= −0.29, 95% CI −0.62 to 0.05, P=0.10)
How many arms should a correct placebo controlled trial have?
Describe the three arms in correct clinical trial design
Arm 1: Intervention/treatment
Arm 2: Placebo (matched for “non-specific effects” e.g., setting, communication, credibility, appearance - anything that can affect expectations or motivation. Must be double blind (i.e. to patients and professionals to control for expectations).
Arm 3: No treatment (e.g., waiting list) controls for regression to the mean, spontaneous remission (e.g. practice effects, development of expertise) and unknown parallel interventions
Give two factors which could effect placebo effects
- Treatment Characteristics: shape, size and colour of drug
- Health Care Settings: care at home/ hospital, lay out of, wards etc.
- Patient Characteristics: beliefs, expectations anxiety levels etc.
- HCP Characteristics: gender, status, beliefs and job satisfaction
- HCP-Patient Relations e.g. information provision, reassurance, compassion, changing expectations etc
Give two of the BCT taxonomies which could be relevant for placebo effects
What did the Di Blasi (2001) Systematic Review show regarding placebo effects?
- 25 RCTs
- 19 manipulated treatment expectancy
- Mainly cog care but 4 manipulated cognitive and emotional care.
- Ten found sig effect on health outcomes (2/10 high quality trials).
- Nine no sig differences (5 high quality trials).
What are some potential ethical considerations regarding placebos
Rothman, K. J. (1996)
- Is it ethical to offer patients treatments that have no known beneficial effect even when they consent?
- Is it ethical to ask patient to consent to placebo treatments that may have damaging effects - e.g. placebo surgery?
- Is it ethical not to run placebo trials of treatments proposed for widespread use?
Can placebos work without deception?
Kaptchuk (2010)
- Two-arm RCT.
- N = 80 patients with IBS.
- Arm 1: Pills presented as “placebo pills made of an inert substance that have been shown in clinical studies to produce significant improvement in IBS symptoms through mind-body self-healing processes.”
- Arm 2: No-treatment controls with the same quality of interaction with providers.
- Significantly higher mean IBS global improvement scores in arm 1 at 21- day endpoint (p=.002).
