Placebo & the Placebo Effect

Placebo & the Placebo Effect

1. Definition, etymology & terminology

• A placebo is any component of therapy that is without specific biological activity for the condition being treated — the standard clinical-pharmacology definition; it is not limited to a sugar pill but extends to any inert vehicle for treatment by suggestion (B&B Ch 2, p.15).
• KDT's exam-tuned definition: a placebo is "an inert substance which is given in the garb of a medicine"; it works by psychodynamic (not pharmacodynamic) means and "often produces responses equivalent to the active drug" (KDT 8e Ch 5, p.77).
• Etymology — placebo is Latin for "I shall please" (more fully "shall be pleasing or acceptable"); the patient responds to the whole therapeutic setting, and the placebo effect largely depends on the physician–patient relationship (KDT 8e Ch 5, p.77; B&B Ch 2, p.15 footnote).
• A placebo medicine is a vehicle for 'cure' by suggestion, and is surprisingly often successful, if only temporarily (B&B Ch 2, p.15).
• The placebo effect is the (favourable) psychological/physiological response to the act of medication itself rather than to any pharmacological action; the placebo response (G&G's term) may involve objective physiologic and biochemical changes as well as changes in subjective complaints (Katzung 16e Ch 1, p.14).
• Nocebo (Latin: nocebo = "I shall injure") is the converse of placebo — the negative psychodynamic effect, an adverse response evoked by a pessimistic patient attitude or loss of faith in the medication/physician; the nocebo effect can oppose the therapeutic effect of active medication (KDT 8e Ch 5, p.78; B&B Ch 2, p.15 — "negative placebo or nocebo effect").
• The nocebo term is little used in the older literature, but is the standard term for placebo-associated adverse events — subjective "toxicity" such as stomach upset, insomnia, sedation (B&B Ch 2, p.15; Katzung 16e Ch 1, p.14).
• All treatments carry a placebo component — physiotherapy, psychotherapy, surgery, entering a patient into a therapeutic trial, even the personality and style of the doctor — but the effect is most easily investigated with drugs, because the active drug and the inert dummy can be made to appear identical, allowing controlled comparison (B&B Ch 2, p.15).