Placebos in 19th century medicine: a quantitative analysis of the BMJ.

Objective: To provide the first quantitative data on the use of the term "placebo" in the 19th century.

Design: Computer search of BMJ's archival database from January 1840 (the first issue) through December 1899 for uses of the words "placebo(s)." Grounded theory was used to categorise the implications of uses of the term.

Nonconscious activation of placebo and nocebo pain responses.

The dominant theories of human placebo effects rely on a notion that consciously perceptible cues, such as verbal information or distinct stimuli in classical conditioning, provide signals that activate placebo effects. However, growing evidence suggest that behavior can be triggered by stimuli presented outside of conscious awareness. Here, we performed two experiments in which the responses to thermal pain stimuli were assessed.