The effect of positive, neutral, and negative expectations about spinal manipulative therapy on pain intensity in...

Spinal manipulative therapy (SMT) has favorable, but small effects on pain intensity to treat chronic low back pain (CLBP). However, there is the potential for these effects to be enhanced by manipulating treatment expectations. Our objective was to investigate the effect of verbally delivered treatment expectations in association with SMT on pain intensity for individuals with CLBP. Our sample consisted of sixty participants who were randomly allocated to three groups in which verbally delivered expectations (positive [PEG], neutral [NEUG], and negative [NEG]) were administered by video before one session of SMT. Pain intensity (primary outcome), global perceived effect (GPE) of improvement, disability, participants' expectations, and empathy as secondary outcomes were assessed immediately post-treatment and pain intensity, GPE, and disability at the 3-month follow-up. Participants were interviewed about their perceptions regarding the videos. Pain intensity significantly decreased in the PEG and NEUG immediately after the SMT session (mean difference=MD), PEG - MD=-1.9 [95% CI -3.4 - -0.3] and NEUG - MD=-1.6 [95% CI -3.2 - -0.05], both when compared to the NEG. However, these findings weren't maintained at the 3-month follow-up. No significant changes in GPE and disability were observed between groups. Our findings suggest that positive and neutral verbally delivered treatment expectations resulted in short-term SMT hypoalgesia compared to negative expectations; however, these effects did not persist at 3-month follow-up. Such results suggest that both positive and neutral SMT-related expectations should be adopted when communicating the expected treatment effects to patients. CLINICAL TRIALS REGISTRATION NUMBER: NCT05996991, protocol registration: August 2023, study start date 1st October, 2023 PERSPECTIVE: Our findings showed that using positive or neutral verbally delivered expectations has the potential to enhance short-term hypoalgesia associated with SMT in CLBP.