Placebo & the Placebo Effect

Definition, etymology & terminology

• Definition — a placebo is any component of therapy without specific biological activity for the condition being treated — not just a sugar pill but any inert vehicle for treatment by suggestion; KDT's exam phrasing is "an inert substance given in the garb of a medicine" that works by psychodynamic, not pharmacodynamic, means and often produces responses equivalent to the active drug.
• Etymology — Latin placebo = "I shall please"; the patient responds to the whole therapeutic setting, and the effect largely depends on the physician–patient relationship — a placebo medicine is a vehicle for 'cure' by suggestion, surprisingly often successful, if only temporarily.
• Placebo effect vs response — 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) may involve objective physiologic and biochemical changes as well as changes in subjective complaints.
• Nocebo — Latin nocebo = "I shall injure" — the converse of placebo, a negative psychodynamic response from a pessimistic attitude or loss of faith in the medication; it can oppose the therapeutic effect of active medication and is the standard term for placebo-associated adverse events (stomach upset, insomnia, sedation).
• All treatments carry a placebo component — physiotherapy, psychotherapy, surgery, even entering a patient into a trial and the personality of the doctor all carry a placebo element — but it is most easily investigated with drugs, because an active drug and an inert dummy can be made to appear identical for controlled comparison.