What's the placebo effect worth?

Earlier this year a study in the BMJ examining pain relief from analgesics showed that just informing people that a codeine product they were taking (actually a placebo) was worth $2.50rather than 10 cents increased the proportion of people who reported pain relief from 61% to 85.4%.So reducing the "price" of the placebo may have reduced the pain relief induced.

Waber RL, Shiv B, Carmon Z, Ariely D. Commercial features of placebo and therapeutic efficacy. JAMA 2008;299:1016-7.

A second more recent study by Kaptchuk et al. (2008)has shown a 'dose dependence' of placebo effects on pain relief dependent on if the patient was assigned to a waiting list (observation), placebo acupuncture alone ("limited"), or placebo acupuncture with a patient-practitioner relationship augmented by warmth, attention, and confidence ("augmented"). The proportion of patients reporting adequate relief were 28% on waiting list, 44% in limited group, and 62% in augmented group (P<0.001 for trend).

So it does appear that the placebo effect is still with us despite calls for it's demise though separating the effects of therapeutic rituals, patient-practitioner interaction, observation/assessment (or the “Hawthorne effect”, initially describing “an increase in worker productivity produced by the psychological stimulus of being singled out and made to feel important”) or investment in ones health, an explanation which seems plausible from the Ariely study.