Negative language use of the physiotherapist in low back pain education impacts anxiety and illness beliefs: A randomised controlled trial in healthy respondents

Objective: This study aimed to determine the effect of physiotherapists' negative language use on nocebo effects of state anxiety and illness beliefs.

Methods: A web-based randomised controlled trial included adults without recent musculoskeletal pain. The intervention was a short educational video about low back pain using negative language (nocebo condition: n = 87) versus a video using neutral or positive language (control condition: n = 82). State anxiety was assessed using the State-Trait Anxiety Inventory. Illness beliefs were assessed using the Illness Perception Questionnaire.

Results: Nocebo and control groups differed in outcome measures (MANOVA Pillai's trace = 0.22, F = 4.98; df = (9,159), p < 0.001). Post-hoc analyses showed a medium to large effect for the nocebo condition on anxiety (d = 0.71, 95% CI 0.4 -1.0). The nocebo group also had higher scores in three illness beliefs: beliefs on timeline (d = 0.45, 95% CI 0.14 - 0.75), treatment control (d = 0.43, 95% CI 0.12 - 0.74) and concern (d = 0.47, 95% CI 0.16 - 0.78).

Conclusion: Physiotherapists' use of negative language contributes directly to a higher state anxiety and illness beliefs that can trigger the nocebo effects in the recipient PRACTICE IMPLICATIONS: Negative language use should be avoided.