Clinical trials of post-traumatic stress disorder (PTSD) show a high rate of placebo response, ranging from 19% to 62% (Ipser & Stein, 2012; Kelmendi et al., 2016; Sher, 2004). Despite these placebo responses across a number of clinical trials, nothing is known about their underlying mechanisms. In fact, the clinical trial setting does not allow us to differentiate between placebo effects due to psychological factors such as patients’ expectations and other phenomena such as spontaneous remission and regression to the mean. The recent explosion of placebo research and the shift in the conceptualization of the placebo effect in several medical conditions, such as pain and motor disorders, makes us understand that their psychological and neurobiological underpinnings can be investigated in some detail. Indeed, what we have learned over the past few years is that different brain mechanisms are at work during the placebo response (Benedetti, Amanzio, Rosato, & Blanchard, 2011; Benedetti, Carlino, & Piedimonte, 2016; Wager & Atlas, 2015).
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