Elsevier

Journal of Affective Disorders

Volume 238, 1 October 2018, Pages 111-117
Journal of Affective Disorders

Research paper
Treatment credibility, expectancy, and preference: Prediction of treatment engagement and outcome in a randomized clinical trial of hatha yoga vs. health education as adjunct treatments for depression

https://doi.org/10.1016/j.jad.2018.05.009Get rights and content

Highlights

  • We conducted an RCT of yoga vs. health education for people with depression.

  • Higher expectancies for improvement were associated with more improvement with yoga.

  • Expectancy for improvement was not associated with improvement in the control arm.

  • There was a trend for a similar pattern for credibility.

  • Expectancy and credibility were not associated with intervention adherence.

Abstract

Background

Hatha yoga may be helpful for alleviating depression symptoms. The purpose of this analysis is to determine whether treatment program preference, credibility, or expectancy predict engagement in depression interventions (yoga or a control class) or depression symptom severity over time.

Methods

This is a secondary analysis of a randomized controlled trial (RCT) of hatha yoga vs. a health education control group for treatment of depression. Depressed participants (n = 122) attended up to 20 classes over a period of 10 weeks, and then completed additional assessments after 3 and 6 months. We assessed treatment preference prior to randomization, and treatment credibility and expectancy after participants attended their first class. Treatment “concordance” indicated that treatment preference matched assigned treatment.

Results

Treatment credibility, expectancy, and concordance were not associated with treatment engagement. Treatment expectancy moderated the association between treatment group and depression. Depression severity over time differed by expectancy level for the yoga group but not for the health education group. Controlling for baseline depression, participants in the yoga group with an average or high expectancy for improvement showed lower depression symptoms across the acute intervention and follow-up period than those with a low expectancy for improvement. There was a trend for a similar pattern for credibility. Concordance was not associated with treatment outcome.

Limitations

This is a secondary, post-hoc analysis and should be considered hypothesis-generating.

Conclusions

Results suggest that expectancy improves the likelihood of success only for a intervention thought to actively target depression (yoga) and not a control intervention.

Introduction

Major depression is a complex phenomenon that involves the interplay of physical, emotional, and cognitive symptoms. Beliefs about a treatment's efficacy may interact with the treatment itself to determine the actual impact of that treatment. When a depressed patient expects that her/his depression symptoms will improve with a given treatment, be it psychotherapy or medications, this may in fact increase the chances that the patient's depression symptoms do improve (Rutherford et al., 2010). Consistent with this, the odds of being considered a treatment responder are higher in trials that compare two active antidepressant medications than they are in the medication arms of randomized, double-blind, placebo-controlled trials (Rutherford et al., 2009). Credibility is a related but distinct construct, and refers to “how believable, convincing, and logical the treatment is” (Kazdin, 1979). Across different types of psychotherapies and psychiatric disorders, early patient perceptions of treatment credibility predict symptom change over time (Mooney et al., 2014).

Patient preference may also predict treatment response. That is, patients who receive a preferred depression treatment (i.e., “concordance”) might show better outcomes than those who receive a non-preferred treatment in a randomized trial. Empirical findings provide mixed support for this hypothesis (Winter and Barber, 2013). A meta-analysis that included 12 studies of depression treatment preference demonstrated a significant but small (Cohen's d = 0.17) effect of concordance on outcome (Lindhiem et al., 2014).

Expectancy, credibility, and concordance may also exert an indirect effect on symptomatic outcome through higher treatment adherence or engagement, or decreased likelihood of study dropout. For example, in a study of internet-based CBT for social anxiety disorder, higher treatment credibility was associated with higher rates of adherence (El Alaoui et al., 2015). Other studies have found that concordance or strength of preference is associated with higher levels of adherence (Hunot et al., 2007, Raue et al., 2009) or lower likelihood of dropout (Dunlop et al., 2017, Kwan et al., 2010), although there are studies that fail to support this hypothesis (Winter and Barber, 2013). A meta-analysis of 9 studies found that concordance significantly predicted treatment completion, with an odds ratio of 1.42. This is a small effect size (Lindhiem et al., 2014). Thus, expectancy, credibility and concordance could lead to higher rates of treatment engagement or study completion, which in turn may lead to better overall outcomes and symptom reduction.

There is increasing evidence that hatha yoga may serve to alleviate depression symptoms (Cramer et al., 2017, Cramer et al., 2013, Uebelacker et al., 2016). Hatha yoga is the most common type of yoga practiced in the U.S., with common styles including Kripalu, Iyengar, Vinyasa, or Viniyoga. Hatha yoga is intended to promote good physical, mental, and spiritual health, and includes physical postures (asanas) and breathing exercises (pranayama), and may also include meditation. Like other types of treatments, expectancies, credibility, or preferences may enhance or detract from the ability of yoga to have an impact on depression. Starting a yoga program with the expectation that it may be helpful could exert an antidepressant effect in and of itself, or through greater engagement in the yoga program. There may be a fair degree of between-person variability in credibility and expectancy for a non-traditional treatment such as yoga.

We are aware of only one existing study that examined expectancy and credibility in the context of yoga for depression. de Manincor et al. (2016) randomized 101 individuals with elevated depression or anxiety symptoms to either a 6-week yoga intervention or a waitlist control group. Although the yoga group showed significantly greater reductions in depression severity, credibility and expectancy were not associated with outcome.

For the current study, we analyzed data from a recently completed randomized control trial of adults with major depression who remained persistently depressed despite antidepressant medication treatment (n = 122). In the parent study, participants were assigned to one of two adjunctive interventions: weekly hatha yoga classes or a health education control class called the Healthy Living Workshop (HLW) (Uebelacker et al., 2017b). Although both types of classes were designed to promote good health, we hypothesized that the yoga intervention would more directly target depression symptoms. We found that, although the groups did not differ on depressive symptoms specifically at the end of the 10-week intervention period, the yoga group had significantly lower average depressive symptoms over time during the combined acute treatment phase and 6-month follow-up period relative to the health education control group. Related, there were significantly more treatment responders in the yoga group at 3-month and 6-month follow-up. Building on this prior work, the aims of the current study were to: 1) compare groups in concordance, credibility, and expectancy at the beginning of the intervention period; 2) examine whether concordance, credibility, or expectancy predicted number of classes attended in either study arm; and 3) examine whether concordance, credibility, or expectancy predicted depression outcome in either treatment arm. In the yoga group only, we also examined whether concordance, credibility, or expectancy predicted average minutes per week of home yoga practice (another index of treatment engagement). “Concordance” was a binary variable representing whether a participant's treatment preference matched the group to which he/she was assigned. We assessed treatment preference prior to randomization, and we assessed credibility and expectancy of the assigned intervention (yoga or HLW) after participation in a first session. We hypothesized that: 1) relative to HLW, the yoga intervention would show greater concordance at baseline, and greater credibility and expectancy after the first session; 2) these three variables would predict number of classes attended in both arms and amount of home yoga practice in the yoga arm; and 3) these three variables would predict outcome in both arms.

Section snippets

Methods

The Institutional Review Board of Butler Hospital approved the study. This trial is registered at clinicaltrials.gov (NCT01384916). We recruited participants from the local community. Advertisements presented study interventions with equipoise, using the rationale that both yoga and HLW were designed to promote good physical and mental health. Once participants understood the nature of the study, signed informed consent forms, and were determined to meet most eligibility criteria (Baseline 1

Demographics and clinical characteristics at baseline

Participants included 103 women and 19 men. Participants were Black or African American (n = 4), White (n = 103), or other or multiracial (n = 15). Six participants were Latino. Most participants (n = 75) had chronic depression. Mean level of depression symptoms on the QIDS at baseline was 12.87 (SD = 2.78). There were no significant differences between groups on these or other baseline demographic or clinical characteristics (Uebelacker et al., 2017b).

Other treatment during study participation

As reported in our previous publication (

Discussion

In this study, we found the expectancy that an intervention for depression would be helpful in fact predicted a better outcome in terms of symptom reduction, but only for the group that received yoga classes, and not for the group that received the health education control condition. We found a non-significant but similar trend for credibility. The fact that expectancy did not predict outcome for individuals in the health education group suggests that the expectancy may improve the likelihood

Conclusion

Credibility and expectancy have often been conceptualized simply as unwanted nuisance variables. That is, in behavioral trials, researchers struggle to match the credibility and expectancy for the control condition to that of the experimental intervention condition. Certainly, one does not want to offer a control intervention that has no credibility whatsoever. However, given the potential impact of patients’ perceptions regarding an intervention's credibility, and expectations that the

Financial support

This work was supported by the National Institutes of Health [R01NR012005]. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

Author statement

The manuscript has been read and approved by all named authors. All authors have materially participated in this research.

Contributors

  • Lisa Uebelacker is responsible for the design of the parent study, oversight of data collection, design of the analyses reported in this paper, data analysis, data interpretation, and preparation of this manuscript.

  • Lauren Weinstock is responsible for the design of the analyses reported in this manuscript, data interpretation, and review of this manuscript.

  • Cynthia Battler is responsible for the design of the analyses reported in this manuscript, data interpretation, and review of this manuscript.

Funding

This work was supported by the National Institutes of Health [R01NR012005]. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

Acknowledgments

We would like to acknowledge the many other co-Investigators, research staff, yoga and HLW instructors, and participants in the parent study

Declarations of interest

Dr. Uebelacker's spouse is employed by Abbvie Pharmaceuticals. Other authors have no conflicts of interest to disclose.

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