Nordisk medicin
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It is well documented that placebo represents Pavlovian conditioned reflexes activated by positive anticipation of healing. The pain-relieving effects of placebo are due to a psychical activation of the endogenous opioid-serotonergic, pain-inhibitory descending system. The opposite effect is nocebo, a term introduced in 1961 by Kennedy. ⋯ In a setting where the animal has no control over an aversive stimulus, as in inescapable foot shocks, nocebo-effects predominate. It is postulated that noradrenergic neurons in locus coeruleus in the brain stem are involved in the production of nocebo-effects. The "placebo-system" and the "nocebo-system" exert a reciprocal inhibition at a brainstem level (Figure 3).