Placebo and nocebo effects are currently within the focus of clinical and experimental pain research. Neurophysiological and psychophysiological mechanisms might play an important role. Placebo and nocebo effects might be mediated through the descendent inhibitory pain pathway via endogenous opioids. Apart from that three different psychological mechanisms might be relevant for placebo and nocebo effects: classical conditioning, social learning and pain expectation. An open analgesic drug application, detailed patient information about efficacy and possible adverse events (without an extensive focus on it) of perioperative analgesic drugs and interventions and an active involvement of the patient in pain therapy (e.g. by using patient-controlled analgesia) might improve acute pain therapy via an additive placebo effect (by around 30%).
