Beliefs in a trial of treatment for pain

Background
Beliefs about treatments in unblinded randomised controlled trials can influence treatment effectiveness, and ideally should be measured. Beliefs may affect compliance, which is necessary for effectiveness, and can in turn be affected by having experience of a treatment.
Aims
To understand the role of treatment beliefs in a trial of telephone-delivered cognitive behavioural therapy (tCBT) to prevent chronic widespread pain (CWP). Specifically, to test if beliefs differed between treatment arms, at the start of treatment and in changes post-allocation, and if they were associated with outcome.
Method
The MAmMOTH study was a trial of tCBT for prevention of CWP in people at high risk. Patients with a number of risk factors for developing CWP were identified by survey of those registered at GP practices in Scotland. Potential participants were sent a short version of the Treatment Beliefs Questionnaire (TBQ) with the study invitation, to measure beliefs about trial treatments – tCBT (referred to as “talking therapy”) and usual care (UC). The short TBQ consists of four statements with a 5-point response scale (Strongly Disagree, Disagree, Neither Agree nor Disagree, Agree, Strongly Agree) scored (1-5) such that high scores represent positive beliefs about treatment. Participants were randomly allocated tCBT or UC. Those allocated tCBT had initial assessment with a therapist by telephone followed by six weekly-sessions, with booster sessions at 3 and 6 months. Participants were considered to have completed treatment if they attended the initial assessment and at least two of any sessions. Those allocated UC received no additional intervention. Questionnaires at 3, 12 and 24 months recorded health, pain status, and the long version TBQ. For this analysis a positive outcome was defined as a report of ‘much’ or ‘very much better’ change in global impression of health on a 7-item Likert scale.
Scores of the short TBQ were calculated for each time point. Positivity towards each treatment was compared between those in each treatment arm using regression models adjusted for age, gender, number of CWP risk factors, GP practice, and, at follow-up, baseline TBQ. In the tCBT arm, positivity toward tCBT was compared at each timepoint between completers and non-completers. Logistic regression models assessed whether baseline TBQ for allocated treatment was associated with outcome, and whether concurrent attitudes towards allocated treatment were associated with outcome at each time point, after adjustment.
Result
Baseline TBQ was available for 364 participants in each treatment arm. Positivity towards UC did not differ at any timepoint between those allocated tCBT and UC. Positivity toward talking therapy did not differ between treatment arms at baseline (3.29 in tCBT vs 3.26 in UC, adjusted mean difference 0.03, 95% confidence interval -0.07–0.13) but did at 3 months (3.60 vs 3.18, 0.39, 0.29-0.49), 12 months (3.56 vs 3.12, 0.40, 0.30-0.51) and 24 months (3.53 vs 3.13, 0.36, 0.24-0.48). In tCBT, completers (n=247) differed from non-completers (n=119) in positive beliefs towards tCBT at all timepoints: at baseline 3.37 in completers vs 3.11 in non-completers (adjusted mean difference 0.24, 0.09-0.38), at 3 months 3.70 vs 3.10 (0.48, 0.28-0.67), at 12 months, 3.73 vs 2.90 (0.69, 0.49-0.90), and at 24 months, 3.64 vs 2.99 (0.48, 0.24-0.71). Baseline positivity towards allocated treatment was not associated with positive outcomes. Concurrent positivity towards allocated treatment was associated with outcomes at each timepoint for tCBT, odds ratios 3.56 (2.11-6.01), 2.59 (1.71-3.92), and 3.33 (1.89-5.88), and at 3 months for UC 1.99 (1.22-3.22).
Conclusion
Experiencing tCBT was associated with an increase in positivity towards it, and positive beliefs are associated with treatment compliance and better outcomes. These findings are important for patients with pain as they show that having experience of tCBT might improve positivity toward it.