Studies on how psychologic factors influence the placebo effect have shown conflicting results in an experimental setting. Pessimists are more likely to experience a nocebo effect (feel worse after an inert intervention), whereas other studies suggest that patients with more symptoms of depression or anxiety or greater neuroticism have a greater response to a placebo. This is important because treatment benefits are potentiated by placebo effects, and optimal utilization of this phenomenon may improve clinical outcomes.
(1) What psychologic factors are associated with a decrease in magnitude of limitations (Disabilities of the Arm, Shoulder and Hand [DASH] score) and pain intensity (visual analog scale [VAS] for pain) after placebo injections for the treatment of painful nontraumatic upper extremity conditions? (2) What psychologic factors are associated with achieving a minimum clinically important difference (MCID) in disability and pain intensity?
We performed a secondary analysis of data acquired in two prospective, double-blind, randomized controlled trials of patients with lateral elbow pain, trapeziometacarpal arthrosis, and de Quervain tendinopathy who received a single injection of dexamethasone and lidocaine or lidocaine alone (placebo). One hundred six patients were included between June 2003 and February 2008. Sixty-three patients (59%) received dexamethasone and lidocaine, and we analyzed the subset of 43 patients (41%) who received lidocaine alone. The primary outcomes of interest were the DASH questionnaire and the VAS for pain measured three times: when they received the injection, between 1 and 3 months after the injection, and between 5 and 8 months after the injection. Seven patients missed the first followup visit and 14 patients missed the second visit. Based on previous research, we chose a MCID threshold of 10 for the DASH and a threshold of 1.0 for the VAS score. In bivariate analysis, we accounted for sex, race, marital status, degree, education, work status, pretreatment pain, diagnosis, symptoms of depression (Center of Epidemiologic Studies–Depression Scale), coping strategies in response to nociception (Pain Catastrophizing Scale), and personality traits (measured with the Multidimensional Health Locus of Control scale and the Eysenck Personality Questionnaire-Revised score). Variables with p values < 0.10 in bivariate analysis were included in the multivariable regression models. An a priori power analysis showed that a sample of 43 participants provides 80% statistical power, with α set at 0.05, for a regression with five predictors if the depression score would account for 15% or more of the variability in pain score. We used multiple imputations (imputations = 50) for a total of 66 (8.5%) missing or incomplete questionnaires.
In the final multivariable models, no psychologic factors were associated with a change in DASH score between injection and followup, and no factors were associated with greater decrease in pain intensity. After injection, no psychologic factors were independently associated with achieving a MCID in the DASH and VAS.
Our study confirms that patient factors are less important mediators of the placebo effect than clinician factors. In other words, clinician warmth and competence can help diminish symptoms and limitations of people in various states of mind, even when using inert or ineffective treatments.
Level II, therapeutic study.
Department of Surgery and Perioperative Care, Dell Medical School, The University of Texas at Austin, Austin, TX, USA
D. Ring, Department of Surgery and Perioperative Care, Dell Medical School, The University of Texas at Austin, Health Discovery Building, MC Z0800, 1701 Trinity Street, Austin, TX 78712, USA, email: David.Ring@austin.utexas.edu
One of the authors (DR) received royalties from Tornier (formerly Wright Medical; Memphis, TN, USA) for elbow plates in the amount of less than USD 10,000 per year and from Skeletal Dynamics (Miami, FL, USA) for an internal joint stabilizer elbow in the amount of less than USD 10,000 per year. One of the authors certifies that he (DR) is a Deputy Editor for Hand and Wrist, Journal of Orthopaedic Trauma, and Clinical Orthopaedics and Related Research® and has received or may receive payments or benefits in the amount of USD 5000 per year. One of the authors certifies that he (DR) received honoraria from meetings of AO North America (Wayne, PA, USA), AO International (Davos, Switzerland), and various hospitals and universities. One of the authors certifies that he (TT) received payments in the amount of less than 10,000 USD per year from AO Trauma (Dubendorf, Switzerland), DePuy Synthes (West Chester, PA, USA), and PATIENT+ (The Hague, The Netherlands).
All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research® editors and board members are on file with the publication and can be viewed on request.
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Each author certifies that his institution approved the human protocol for this investigation and that all investigations were conducted in conformity with ethical principles of research.
Received April 11, 2018
Accepted July 11, 2018