- Placebo Effect, Honest Placebo, Open-label Placebo
- Placebo effect and its impact on the overall treatment effect
- Placebo Effect and The Choice of Placebo
An AWC study uses a design that permits a valid comparison with a control to provide a quantitative assessment of a drug’s effect. In the context of psychedelic drug development, the use of a traditional placebo as a control can be problematic for assessing efficacy. Subjects receiving an active drug experience functional unblinding because of the intense perceptual disturbances that can develop; those who receive a placebo in the context of high expectancy may experience a nocebo effect (i.e., worsening symptoms as a result of knowing they did not get active treatment). However, an inactive control allows for better contextualization of any safety findings. Alternatives to an inert placebo (e.g., subperceptual doses of a psychedelic drug, other psychoactive drugs that mimic some aspects of the psychedelic experience) may be considered as well.
Aspect |
Placebo Effect |
Nocebo Effect |
Definition |
A positive
response to an inactive treatment, often due to the person's belief in the
treatment's effectiveness. |
A negative
response to a treatment, often due to the person's belief that the treatment
will cause harm or have adverse effects. |
Psychological
Mechanisms |
Expectation
of improvement, conditioning, and the power of suggestion. |
Expectation
of harm, conditioning, and the power of suggestion. |
Potential
Chemical Mechanisms |
Belief and
expectation trigger the release of endorphins, dopamine, and other
neurochemicals, leading to perceived improvement in symptoms. |
Belief and
expectation trigger the release of stress hormones (e.g., cortisol) and
activate the brain’s pain pathways, leading to perceived worsening of
symptoms. |
Common
Occurrences |
In clinical
trials, as a control group receiving an inactive treatment (e.g., sugar
pill). |
In clinical
trials, when participants experience side effects despite receiving an inactive
treatment, or when they're informed about potential side effects |
Impact on
Treatment |
Can lead to
an actual improvement in symptoms or a perceived improvement in well-being |
Can cause or
exacerbate symptoms, leading to a perceived worsening of health |
Importance in
Research |
Helps
determine the true efficacy of a treatment by comparing it to the placebo
group |
Highlights
the importance of considering participants' expectations and beliefs when
designing and interpreting clinical trials. |
Clinical Use |
Utilized in
clinical trials as a control to assess the effectiveness of new treatments. |
Considered a
challenge in clinical trials as it can lead to false negative outcomes or
increased reports of adverse effects. |
Impact on Clinical
Trial Outcome |
Making the outcome
measures in placebo group artificially better than what they should be. Underestimating the treatment difference. Lowering the statistical power. |
Making the
outcome measures in placebo group artificially worse than what they should
be. On the efficacy side, overestimate the treatment difference. Increasing the statistical power. |
Ethical
Considerations |
May be
considered deceptive if participants are not informed about the possibility
of receiving a placebo |
Raises
questions about the balance between informing participants of potential side
effects and avoiding the creation of negative expectations |
Examples |
- Feeling
relief from pain after taking a sugar pill, believing it to be a painkiller. -
Experiencing reduced anxiety after receiving a fake treatment, thinking it is
an anti-anxiety medication. |
- Developing
side effects (e.g., nausea, dizziness) after taking a harmless sugar pill,
convinced it is a potent medication. - Perceiving
worsening of symptoms despite receiving an inert substance, assuming it is a
harmful treatment. |
References:
- Wartolowska, Colloca, and Amandzio (2023) Editorial: The nocebo effect and its consequences for clinical trials and clinical practice
- Colloca and Barsky (2020) Placebo and Nocebo Effects
- Colloca and Miller (2011) The nocebo effect and its relevance for clinical practice
- Ferreres, Banos, and Farre (2004)Nocebo effect: the other side of placebo.
- Mitsikostas (2009) Nocebo is the enemy, not placebo. A meta-analysis for the nocebo effect in headaches
- Amanzio, Corazzini, Vase, & Benedetti (2016). A systematic review of adverse events in placebo groups of anti-migraine clinical trials.
- Wolters, Peerdeman, and Evers (2019) Placebo and Nocebo Effects Across Symptoms: From Pain to Fatigue, Dyspnea, Nausea, and Itch
- Hoffman, et al (2022) Vaccine hesitancy prospectively predicts nocebo side-effects following COVID-19 vaccination