Commentary: the use of placebos in psychiatric research

Inpatient's, therapist's and staff's expectations regarding treatment and their effects on placebo response in the psychiatric ward - results from an add-on oxytocin RCT

OBJECTIVES

Patient's and therapist's expectations are considered an important factor influencing placebo response in experimental and therapeutic settings. Nevertheless, the placebo effects of common neurological facilitators that promote treatment efficacy have not been explored. In the present study we examined the estimations of patients, therapists, and staff members, regarding their treatment type and assessed their influence on the facilitating effects of oxytocin.

METHODS

Patients (N = 87) were randomized and double-blindly allocated to receive either oxytocin or placebo, twice daily for a period of four weeks, as part of a larger randomized, double-blind, placebo-controlled trial. Patient's, therapist's and staff's expectations were assessed based on their estimation of treatment type (agent or placebo). Multilevel modeling and univariate and multivariate regression analysis were performed to assess the effects of patient's, therapist's, and staff's estimations on treatment outcome beyond the effects of treatment type.

RESULTS

Staff's, therapist's, and patient's estimations were significantly associated with treatment outcomes. Nevertheless, only therapist's and patient's estimations significantly predicted improvement beyond actual administration, with therapist's and patient's estimations associated with improvement in trait anxiety (STAI-T, B=-1.80, p < .05, and B=-2.02, p < .05, respectively); therapist's estimations were associated with improvement in general distress (OQ-45, B=-3.71, p < .05), and patient's estimations were associated with symptom relief (HSCL-11, B=-0.13, p < .05). Overall, patient's estimations had a higher relative contribution to treatment success, with standardized coefficients across scales ranging from - 0.06 to -0.26.

CONCLUSIONS

The neurobiological factors that promote treatment success are also influenced by patient's and therapist's expectations. Future studies should consider these effects when examining their impact in inpatient settings.

Placebo response in depression

With its naturally fluctuating course, depression is a highly placebo-responsive condition: mean placebo response rates in antidepressant clinical trials are 30% to 40%. We review the history and terminology of placebo and the proposed mechanisms underlying the placebo response, including the physician-patient relationship and biological, sociocultural, and treatment situation factors. We identify the predictors and patterns of placebo response in depressed patients, both within and outside of the clinical trial context, and differentiate between true drug response and placebo pattern response. We discuss the strategies now being advanced to minimize the placebo response given the increased placebo drift reported in recent trials, and the ethical guidelines governing placebo administration. Potential areas for future research include the identification of biological markers of placebo response, such as functional neuroimaging and quantitative electroencephalography, the development and testing of more sophisticated, alternative research designs, and the design of valid biological tools to assess antidepressant efficacy.