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.