Cognitive changes as a result of a single exposure to placebo

Abstract

Placebo has been shown to be a powerful analgesic with corresponding reduction in the activation of the pain matrix in the brain. However, the response to placebo treatment is highly variable. It is unclear how anticipatory and pain-evoked potentials are affected by the treatment and how reproducible the response is. Laser stimulation was used to induce moderate pain in healthy volunteers. We induced placebo analgesia by conditioning subjects to expect pain reduction by applying a sham anaesthetic cream on one arm in conjunction with a reduced laser stimulus. Pain ratings were assessed before, during and after treatment. Using lectroencephalography (EEG) we measured anticipatory neural responses and pain-evoked potentials to laser heat to determine how expectation of analgesia affected the response to a placebo manipulation. This was a reproducibility study and as such the experimental procedure was repeated after a minimum gap of 2 weeks. Significant reductions in pain-evoked potentials were shown after treatment. The anticipatory responses did not change after treatment for the control and sham-treatment groups in the first session but were significantly lower in the repeat session relative to the first session in the sham-treatment group only. A significant correlation was found between the reduction in state anxiety in the repeat session relative to the first and the reduction in the anticipatory response in the sham-treatment group. Receiving a placebo treatment appears to cause a lasting change in the cognitive processing of pain for at least 6 weeks. This cognitive change may be facilitated by a change in state anxiety.

The association between resting functional connectivity and dispositional optimism

“…The current study used the Chinese version of LOT-R (Life Orientation Test-Revised) [39, 40] to assess participants’ levels of dispositional optimism [2, 12]. The LOT-R includes 10 items that evaluate generalized expectancies for either positive or negative outcomes.…”

“…Although extreme optimism can be harmful as it can promote an underestimation of risk and poor planning [6, 7], moderate optimism can motivate adaptive behavior in the present towards a future goal [7], and is beneficial to both physical and psychological wellbeing [8–10]. Optimists tend to have lower self-reported depressive symptoms [11], whereas pessimists report more negative expectations of the future [12–14]. Additionally, optimists were observed to have a lower risk of cardiovascular disease compared with pessimists [11, 15], and to be associated with lower incidence rate of complications and better recovery after surgery[16].…”

What’s in a word? How instructions, suggestions, and social information change pain and emotion

“…Following this placebo administration, this instruction is often reinforced by lowering stimulus intensity (unbeknown to the participant), leading the participant to experience actual relief and attribute it to the placebo (e.g. Atlas et al, 2010; Colloca et al, 2010; Geuter et al, 2013; Koban et al, 2012; Morton et al, 2010; Price et al, 1999; Wager et al, 2004). Despite an important involvement of learning in placebo (Colloca and Benedetti, 2009; Schafer et al, 2015), suggestions are central to placebo and nocebo effects, and can be effective even alone, i.e.…”

The Placebo Effect: Advances from Different Methodological Approaches

“…Some recent studies adopting a pharmacological conditioning with drugs such as morphine (Amanzio and Benedetti, 1999; Benedetti et al, 2007), immunosuppressor cyclosporin A (Goebel et al, 2002; Pacheco-Lopez et al, 2009), dopamine-agonist apomorphine (Benedetti et al, 2004), benzodiazepine receptor agonist midazolan and antagonist flumazenil (Petrovic et al, 2002), found that the conditioned placebo responses mimic drug effects, thus providing evidence that an important factor in eliciting bodily placebo responses is the previous exposure to effective treatment. Conditioned placebo analgesic responses not only appear sensitively shaped by prior exposure to treatment effectiveness (Colloca and Benedetti, 2006; Morton et al, 2010b; Morton et al, 2010a), but also by the number of learning trials (Colloca and Benedetti, 2006; Colloca et al, 2008a; Colloca et al, 2008b; Colloca and Benedetti, 2009; Colloca et al, 2010; Colloca and Miller, 2011).…”

“…Importantly, higher empathy yielded stronger placebo responses, supporting a link between the ability to modify behaviors following social observational learning and empathy. Beyond empathy, some other dispositional traits such as altruism (Mackenbach, 2005) and optimism (Geers et al, 2005; Geers et al, 2010; Morton et al, 2010b) seem to play a role, indicating that emotions and personality traits modulate expectations and placebo-induced behavioral changes.…”