Placebo Effect Flashcards
Define the placebo effect
The placebo effect refers to the phenomenon where a patient’s symptoms improve after receiving a treatment with no therapeutic effect, purely due to their belief in its efficacy. This effect highlights the psychological and physiological responses triggered by expectations of healing rather than the treatment itself
List commonly observed placebo mediated phenomena that impact on medical research
Symptom Relief: Pain, nausea, and fatigue reduction.
Psychological Benefits: Mood improvement and reduction in anxiety.
Physiological Responses: Changes in heart rate, blood pressure, and immune responses.
Condition-Specific Responses: Observed in chronic pain, depression, and irritable bowel syndrome
What are some Experimental Evidence for the Reality of the Placebo Effect
Open-Label Placebos: Patients told they are receiving a placebo still show symptom improvements (e.g., in pain and IBS studies).
Sham Surgeries: Patients undergoing fake surgeries (e.g., knee arthroscopy) report improvements comparable to real surgeries.
Classical Conditioning Studies: Participants exhibit physiological responses (e.g., reduced pain) after associating a neutral stimulus with an active drug.
Describe physiological mechanisms that mediate placebo effects:
Expectations: Belief in treatment efficacy drives positive outcomes.
Conditioning: Repeated pairings of treatment cues and symptom relief.
Patient-Practitioner Interaction: Empathy and reassurance boost placebo responses.
Describe Neurobiological Mechanisms that mediate placebo effects:
Endogenous Opioid Systems: Activation in placebo-induced pain relief.
Dopaminergic Pathways: Reward systems engaged by expectations.
Brain Activity Changes: Alterations in the prefrontal cortex and insula.
What is the nocebo effect ?
The nocebo effect is the negative counterpart to the placebo effect, where negative expectations or beliefs about a treatment exacerbate symptoms or cause adverse effects.
Can lead to real physiological and psychological harm.
Commonly observed in drug trials (e.g., side effects reported in placebo arms).
Driven by fear, anxiety, and negative conditioning.
Provide some examples of Experimental Design Strategies to Mitigate the Impact of Placebo Effects
Double-Blind Studies: Both participants and researchers are unaware of group assignments.
Placebo-Controlled Trials: Compare active treatments to placebo groups.
Balanced Expectancy Designs: Equally distribute expectations across groups.
Objective Outcomes: Use biomarkers or quantifiable data to minimize subjective bias.
Give 2 studies that show evidence of Placebo effect:
Benedetti et al. (1996): Showed placebo analgesia was reversed by naloxone, indicating endogenous opioid involvement.
Beecher (1955): Highlighted that 35% of patients experienced placebo-induced relief across 15 trials.
