ABSTRACT
Chronic pain increases the risk of sleep disturbances, depression and disability. Even though medical treatments have limited value, the use of prescription-based analgesics have increased over the recent years. It is therefore important to evaluate the effect of non-pharmacological treatments. A systematic search for studies evaluating the effect of relaxation techniques on chronic pain was conducted. Randomized controlled trials were included. Significant effects on pain, or on pain and one or more secondary outcome measure, were found in 21 studies. Four studies found significant effects on secondary outcome measures only. Four studies showed no significant effects on any outcome measure. Thus, most of the studies reported that relaxation techniques reduced pain and/or secondary outcome measures. However, the included studies have evaluated effects across a wide variety of chronic pain conditions and relaxation techniques. Hence, there is a large degree of heterogeneity among the included studies. This complicates the effect evaluation and makes it difficult to draw a clear and unambiguous conclusion. Relaxation techniques are probably most effective when used through regular and continued practice. Future studies should therefore investigate long-term effects of relaxation technique interventions, evaluate the dose-response relationship and examine efficacy differences across pain conditions and interventions.
ABSTRACT
BACKGROUND: Contextual factors, such as participant/experimenter sex may moderate the placebo effects. We tested whether the participant and experimenter sex modulated placebo effects on experimentally induced pain and associated stress. OBJECTIVE: To investigate if (i) participant sex and (ii) experimenter sex influence placebo analgesia and subjective and physiological stress in two experiments employing a within-subjects and a mixed design, respectively. Placebo effects were investigated in pain reports, stress, and blood pressure. METHODS: Participants received painful stimulations and a placebo cream. In Experiment One (N = 59) participants underwent a placebo condition (PC) and a natural history condition (NHC) in random order. A placebo cream was applied in the PC and then the heat stimulation temperature was surreptitiously lowered. Identical stimulations were administered in the NHC, but with no cream, no information, and no lowered temperature. In Experiment Two, participants (N = 93) were randomly assigned to three groups receiving either a placebo cream with surreptitiously lowered intensity of electric stimuli (Placebo, PG), a placebo cream (Cream-Control, CCG) without changing the stimuli, or lowered intensity, but with no cream (Pain-Control, PCG) in a mixed design. All participants in both experiments received the same stimuli in the post-test as in the pre-test. Four experimenters (two females) in Experiment One, and five experimenters (two females) in Experiment Two conducted the studies. RESULTS: No placebo effect was seen on pain. However, there were placebo effects on stress, moderated by participant and experimenter sex: in Experiment One males in the PC had lower diastolic blood pressure (DBP) compared to males in the NHC. Participants in the PC had lower DBP compared to the NHC when tested by a female. In Experiment Two, participants expected more cream effectiveness when a female experimenter administered it, and reported lower stress in the PG compared to the PCG when tested by females. CONCLUSION: Our findings highlight a distinction between placebo effects on pain and on associated stress. Secondly, female experimenters recorded lower physiological and subjective stress, higher effectiveness expectations, and lower pain from both sexes compared to male experimenters. Possible reasons for the failure to find a pain placebo effect are discussed.
