A dysfunction in conditioned pain modulation (CPM) is believed to be an important mechanism in chronic pain. Few studies investigated the role of expectations in pain modulation, while there are...Show moreA dysfunction in conditioned pain modulation (CPM) is believed to be an important mechanism in chronic pain. Few studies investigated the role of expectations in pain modulation, while there are indications that pain sensitivity can be affected by expectations. The present study examined whether expectations modulated the effect of conditioned pain stimulation. Since earlier research indicated gender differences and physiological stress levels might play a role in CPM as a response to positive or negative information, the present study will take gender differences and objective stress levels (heartrate and skin conductance levels) into account. Healthy participants (57 of each sex) between 18 – 35 years of age were randomly assigned to three experimental groups: 1) participants were told positive expectations, that holding the non-dominant hand in a cold-water bath will decrease the pain intensity of the test stimulus (analgesia group), 2) participants received the information that the conditioned stimuli will increase the pain intensity of the test stimulus (hyperalgesia group), 3) participants received no information about the effect (control condition). Results were analyzed with a mixed ANOVA. The results show that positive or negative expectations modulated the CPM effect compared to the control condition (p = .006). This effect was not dependent on gender. Conditioning stimulation increased skin conductance levels, but not heart rate in the hyperalgesia group. Higher skin conductance levels as a response to negative information were more visible in males compared to females. The present study suggests that inhibitory CPM can be influenced by verbal suggestions, and that a dysfunction of descending inhibitory pathways seems not the only possible cause of a reduced inhibitory CPM. Future research could examine if positive expectations can influence the altered CPM efficacy in patients with chronic pain.Show less
