Which Factors Predict Placebo Response in Anxiety Disorders and Major Depression?

INDUSTRY FUNDING AND PLACEBO QUIT RATE IN CLINICAL TRIALS OF NICOTINE REPLACEMENT THERAPY: A COMMENTARY ON ETTER ET AL. (2007)

“…A number of factors may account for this difference between industry-funded and non-industry trials, such as the characteristics of participants recruited (in particular heaviness of smoking or level of tobacco dependence), the exclusion of participants with confounding comorbidity (such as alcohol abuse or mood disorder) or the number of study sites [2]. Interestingly, we did not observe an association between placebo response rate and either year of publication or whether the study was conducted in the United States, in contrast with recent evidence from trials of antidepressant medication [4,5]. These results suggest that there may be important differences in the design and conduct of industry-sponsored trials compared with nonindustry trials, which impact specifically upon placebo response rates to increase the likelihood of observing a statistically significant treatment effect.…”

Neural Mechanisms of Placebo Anxiolysis

“…We therefore suggest that placebo anxiolysis is an active process requiring top-down cognitive control, supported mainly by frontal substrates. In-line with this hypothesis, functional magnetic resonance imaging (fMRI) studies of placeboinduced reductions in pain and other negative emotional states have consistently found placebo-induced activations in prefrontal and anterior cingulate sites, often correlated with the magnitude of the placebo effect (Wager et al, 2004;Petrovic et al, 2005;Bingel et al, 2006;Zhang et al, 2011;Amanzio et al, 2013) and disruption of prefrontal activity during placebo tasks has been shown to disrupt placebo effects Krummenacher et al, 2010).…”

“…However, little is known about the neural bases of placebo effects in the treatment of fear and anxiety. This is remarkable, because in clinical everyday life placebos are frequently used with the intention to calm anxious patients (Nitzan and Lichtenberg, 2004;Sherman and Hickner, 2008) and placebo effects have been shown to contribute to the pharmacological treatment of anxiety disorders (Stein et al, 2006;Sugarman et al, 2014) and to the pharmacological reduction of postoperative anxiety ).…”

Neuro-Bio-Behavioral Mechanisms of Placebo and Nocebo Responses: Implications for Clinical Trials and Clinical Practice

“…Anxiety Disorders. For anxiety disorders such as generalized anxiety, panic disorder, or social phobia, placebo effects in clinical trials have been reported ranging between 10% and 60% (Loebel et al, 1986;Mavissakalian, 1988;Mellergard and Rosenberg, 1990;Piercy et al, 1996;Huppert et al, 2004;Khan et al, 2005;Stein et al, 2006). Moreover, in RCTs investigating the anxiolytic effect of the benzodiazepine alprazolam, improvement in the placebo arm remained stable after the pill intake was discontinued, whereas patients in the drug arm suffered relapses to baseline levels (Ballenger et al, 1988;Pecknold et al, 1988), indicating that placebo responses in anxiety disorders can indeed be long lasting and clinically relevant.…”