Among acupuncture-naïve persons with chronic low back pain, we found that having higher pre-treatment expectations for the success of acupuncture was associated with higher general expectations for improvement, preference for acupuncture over other back pain treatments, having heard acupuncture was a very effective treatment, and having a positive impression of acupuncture. However, none of these variables was a significant predictor of short or long-term improvement in back-related symptoms or function.
After one treatment, participants’ revised expectations were predictive of only modest improvements in back symptoms at the end of treatment. After five treatments, a stronger association was found between expectation of treatment success for both outcomes at 8 and 52 weeks, likely reflecting participants’ revisions of their expectations to reflect their actual experience. Thus, in our study population, having a highly positive predisposition toward acupuncture did not predict superior outcomes. Although based on a pre-planned analysis of secondary data, this study has notable strengths including a large sample size, high follow-up rates, successful treatment blinding, and inclusion of multiple measures of participants’ beliefs regarding acupuncture’s effectiveness as a therapy for back pain. Furthermore, the consistent results among these measures lend credence to our results.
The inconsistent findings of the three previous studies of acupuncture for persistent musculoskeletal pain that included measures of pre-treatment expectations14–16
could reflect differences in recruitment sources (primary care patients14, 15
versus respondents to advertisements16
) or in how expectations and outcomes were measured.
Kalauokalani et al’s 14
study of patients randomized to massage or acupuncture found those with higher positive pre-treatment expectations of the treatment they received were more likely to have clinically important improvements in function at the end of treatment. Her study included a small fraction of participants who had previously had these treatments (4% of those randomized to acupuncture and 14% of those randomized to massage).
Linde et al’s 16
analysis of data combined from 4 large trials of acupuncture for different musculoskeletal conditions found expectations of improvement asked before treatment and after the third treatment to be predictive of improvement (defined as 50% improvement in pain, the primary outcome) at the end of treatment and 4 months later. Of the 75% of persons expressing positive expectations of acupuncture, (the remainder failed to provide an expectation), 89% expected at least “clear improvement” in their pain. Thus, the patients in Linde’s report appeared substantially more optimistic than those in our study about the benefits of acupuncture for their pain condition. Moreover, about 30% of participants in his study versus none in our study had previously had acupuncture treatments a year or more prior to the study.
In the third study, Thomas et al.15
found that persons randomized to acupuncture who thought acupuncture might help their back problem did little better than those randomized to usual care after 24 months on their primary outcome measure, the Bodily Pain Scale of the SF-36. By contrast, those who did not know whether acupuncture would be helpful were somewhat more likely to benefit if randomized to acupuncture.
Studies of many other treatments for back pain have also failed to provide consistent evidence that optimism about 24, 25
or preference26, 27
for a treatment leads to better outcomes. The disparate results of these studies suggest that the relationship between expectations and preferences for treatment and outcomes is more complex than has been previously thought. 7, 28
Participants’ previous experience with the treatment under study might be expected to influence the observed relationship between treatment expectations and outcomes. Specifically, we suspect that studies including high proportions of participants who have tried the treatment previously (and who therefore probably had positive experiences with the treatment) will be more likely to find a positive correlation between expectation and outcomes than studies including individuals who have had no experience with the treatment. We think that future progress in elucidating the nature of these relationships will require greater consistency in measurement of preferences and expectations as well as more sophisticated models of the interrelationship among patient expectations, treatment outcomes, and the patient-provider relationship. Such models should include potential mediators and moderators of treatment outcome, including prior experience with the therapy, both in general and for the specific condition studied. New questionnaires should be designed to explicitly facilitate the testing of conceptual models linking expectations and preferences to treatment outcomes.
At this early stage of research on patient expectations, we recommend that such instruments include several questions that explore conceptually distinct dimensions of patients’ expectations-related experience. Such pre-treatment measures might include general expectations for improvement in condition, preferred treatment, expectations about the value of the specific treatment, and the possible antecedents for these expectations (e.g., prior experience with therapy, experience of family or friends). If there is interest in how treatment expectations change over time, similar measures could be asked during the course of treatment.
Further work in this area could ultimately have important practical value by helping clinicians better understand the potential clinical benefits of promoting reasonable treatment options that their patients believe will be most helpful. There is limited, but growing evidence that clinicians can either enhance or attenuate their patient’s pre-treatment expectations by the way they interact with them.28
A recent trial of patients with irritable bowel syndrome clearly demonstrated that a supportive patient-provider relationship amplifies treatment benefits for persons receiving a placebo CAM treatment.29
Conceivably, such benefits could be even greater in persons with greater initial optimism about the treatment.
Our study demonstrates that positive pre-treatment beliefs about medical therapies do not always lead to enhanced outcomes, even for CAM therapies. The relationship between patient expectations and treatment outcomes appears to be complex. Advances in this burgeoning area of research will require development of more sophisticated conceptual models and measures of expectation.