, according to investigators.
These findings may improve prediction of placebo responses in IBS, and may help avoid patient-provider “mismatch,” both of which can alter treatment outcomes and confound clinical trial findings, reported lead author Jeffrey M. Lackner, PsyD, chief of the division of behavioral medicine at the University of Buffalo, New York, and colleagues.
“A relatively large (40%) placebo response in IBS trials obscures potentially useful, mechanistic, and pharmacodynamically induced symptom changes among agents that do reach market,” the investigators wrote in Gastro Hep Advances. “This begs the question of what individual difference factors distinguish placebo responders.”
While previous studies have explored placebo patient predictors in IBS, most focused on study design and baseline personal characteristics such as age and sex, with none yielding prognostically reliable findings, according to Dr. Lackner and colleagues. Mid-treatment factors such as patient-provider dynamics have not been featured in published meta-analyses, they noted, despite their potential importance.
University of Buffalo
Dr. Jeffrey M. Lackner
“This limitation partly reflects the demands of efficacy trials that prioritize pre- and posttreatment data over that collected during acute phase, when the putative mechanisms underpinning placebo effects play out,” the investigators wrote. “The expectation that one can benefit from a treatment, for example, is optimally assessed after its rationale is delivered but before a clinically thorough regimen is provided, meaning that it cannot be fruitfully assessed at baseline along with other personal characteristics when treatment rationale is not fully disclosed. The same applies to relational factors such as patient-physician interactions that define the context where treatment is delivered, and placebo response presumably incubates.”
To explore the above factors, Dr. Lackner and colleagues conducted a secondary analysis of 145 patients with Rome III-diagnosed IBS from the Irritable Bowel Syndrome Outcome Study.
During the study, patients were randomized to receive either 10 sessions of clinic-based cognitive behavioral therapy (CBT), 4 sessions of minimal-contact CBT, or 4 sessions of supportive counseling and education without any prescribed behavior changes. Responses were measured by the IBS version of the Clinical Global Improvement Scale, with evaluations conducted at the treatment midpoint and 2 weeks after treatment.
Candidate predictors at baseline included pain catastrophizing, somatization, emotion regulation, neuroticism, stress, and others, while clinical factors included treatment expectancy/credibility and patient-provider relationship.
Responses during treatment were significantly associated with lower somatization and stress level at baseline, as well as greater patient-provider agreement on treatment tasks (P less than .001).
Posttreatment responses were significantly associated with baseline gastroenterologist-rated IBS severity, anxiety, agreement that the patient and the provider shared goals from a provider perspective, and ability to reframe stressful events in a positive light (P less than .001). That ability to reconsider emotions was also associated with a faster placebo response (P = .011).
“The strength of placebo responsiveness is subject to the influence of patient factors that precede treatment delivery (rethinking or reinterpreting stressful situations in everyday life in a way that reduces their subsequent impact) and specific elements of provider-patient interactions that occur while treatment is delivered, particularly practitioners’ estimation that patients agree on their goals and tasks to achieve them,” Dr. Lackner and colleagues concluded. “We believe this line of research can help identify factors that drive placebo response and narrow the patient-provider ‘mismatch’ that undermines the quality, satisfaction, and efficiency of IBS care regardless of what treatment is delivered.”
The study was supported by the NIH. The investigators disclosed no conflicts of interest.
