But analyses of the published data and the unpublished data that were hidden by drug companies reveals that most (if not all) of the benefits are due to the placebo effect.
Antidepressants and the Placebo Effect
Evidence for Opioid-Mediated Placebo Analgesia
In 2005, the first direct evidence of opioid-mediated placebo analgesia was published (Zubieta et al., 2005). In vivo receptor-binding techniques using the radiotracer carfentanil, a µ-opioid agonist, were used to show that a placebo procedure activates µ-opioid neurotransmission in the dorsolateral prefrontal cortex, the anterior cingulate cortex, the insula, and the nucleus accumbens (Fig. 4.7). …
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Open Administration of Placebos Greatly Increases Effectiveness
In postoperative pain following the extraction of the third molar (Levine et al., 1981; Levine and Gordon, 1984), a hidden intravenous injection of 6–8 mg morphine corresponded to an open intravenous injection of saline solution in full view of the patient (placebo). In other words, telling the patient that a painkiller was being injected (with …
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Acupuncture and Placebo Analgia
In another clinical trial, patients were asked whether they considered acupuncture to be an effective therapy in general and what they personally expected from the treatment. Patients with higher expectations about acupuncture experienced larger clinical benefits than those with lower expectations, regardless of their allocation to real or sham groups (Linde et al., 2007). It …
Placebo Conditioning by Means of Functional Magnetic Resonance Imaging
Lui et al. (2010) showed dynamic changes in prefrontal areas during placebo conditioning by means of functional magnetic resonance imaging. Brief laser heat stimuli delivered to one foot, either right or left, were preceded by different visual cues, signaling either painful stimuli alone, or painful stimuli accompanied by a sham analgesic procedure. Cues signaling the …
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Previous Experience and Analgesia
Previous experience can also influence the magnitude of placebo analgesia. In one study, the intensity of painful stimulation was reduced surreptitiously after placebo administration, so leading subjects to believe that an analgesic treatment was effective (Colloca and Benedetti, 2006) (Fig. 4.2C). Fig. 4.2 C. Variability in magnitude of placebo analgesia. Part (C) shows different degrees …
Verbal Suggestion’s Effect on Analgesia
Today it seems clear that the experimental manipulation used to induce placebo analgesia plays a fundamental role in the magnitude of the response. Among the different manipulations that have been performed, both the type of verbal suggestions and the individual’s previous experience have been found to be important. Verbal suggestions that induce certain expectations of …
The Lateral and Medial Pain Systems in Alzheimer’s Disease
The lateral and medial pain systems are affected differently in Alzheimer’s disease. Both the primary somatosensory cortex and some thalamic nuclei, which belong to the lateral pain system, are relatively unaffected by the histological changes that characterize Alzheimer’s disease, thus indicating that a preserved sensory-discriminative function should be expected. By contrast, the intralaminar thalamic nuclei, …
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Bottom-up Processing of Pain
Today we know that there is not a pain center in which the final pain experience emerges, but rather there is a distributed system that is made up of an intricate network of cortical and subcortical areas, each with some specific functions. This network is often referred to as the “pain matrix.” The organization of …
4.1.3 Expectations of improvement may lead to analgesia
Expectation plays an essential role in placebo analgesia. Modulation of pain perception by placebos depends on expectation, as shown in many studies (Kirsch, 1999; Price et al., 1999, 2008). Montgomery and Kirsch conducted one of the first studies in which expected pain levels were manipulated and directly measured (Montgomery and Kirsch, 1997). They used a …
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