I’ve just written a post on one of my favourite topics; the placebo effect.
Triggered by the article Placebo is not what you think, it touches on the use of placebos by medical professionals (currently a banned practice) and the informed use of placebos by heroin addicts. Strangely enough, in the latter case the use by addicts is self-medicated:
Furthermore, studies done in the 1970s showed that when heroin users inject water (sometimes done deliberately to alleviate cravings when drugs are in short supply), they can experience drug-like euphoria and have been observed to show opiate-like physiological signs such as pupil constriction.
This last point also demonstrates that placebo is not solely about expectancy, belief or ‘being fooled’, as the heroin users knew they were injecting themselves with water. Conditioned responses play a role.