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Can a physiologic response outside of conscious control be conditioned to a placebo? Researchers in Germany used a well-established model of conditioned immunosuppression to explore this issue in healthy men.
In one experiment, 35 men received the immunosuppressant cyclosporine A as an unconditioned stimulus (US) paired with a strawberry/lavender-flavored drink (conditioned stimulus; CS). With later exposure to the CS alone, it suppressed T-cell function. This conditioned immunosuppression was extinguished after 14 exposures to the CS without the US.
In another trial using the same conditioning regimen (N=29), extinction was completely prevented when the drink was later paired with an immunosuppressant dose that was too low to affect immune f…