Understanding placebo and nocebo responses for pain management

Placebo analgesia: understanding the mechanisms

Expectations of pain relief drive placebo analgesia. Understanding how expectations of improvement trigger distinct biological systems to shape therapeutic analgesic outcomes has been the focus of recent pharmacologic and neuroimaging studies in the field of pain. Recent findings indicate that placebo effects can imitate the actions of real painkillers and promote the endogenous release of opioids and nonopioids in humans. Social support and observational learning also contribute to placebo analgesic effects. Distinct psychological traits can modulate expectations of analgesia, which facilitate brain pain control mechanisms involved in pain reduction. Many studies have highlighted the importance and clinical relevance of these responses. Gaining deeper understanding of these pain modulatory mechanisms has important implications for personalizing patient pain management.

Modulation of inhibitory corticospinal circuits induced by a nocebo procedure in motor performance

As recently demonstrated, a placebo procedure in motor performance increases force production and changes the excitability of the corticospinal system, by enhancing the amplitude of the motor evoked potentials (MEP) and reducing the duration of the cortical silent period (CSP). However, it is not clear whether these neurophysiological changes are related to the behavioural outcome (increased force) or to a general effect of expectation. To clarify this, we investigated the nocebo effect, in which the induced expectation decreases force production. Two groups of healthy volunteers (experimental and control) performed a motor task by pressing a piston with the right index finger. To induce a nocebo effect in the experimental group, low frequency transcutaneous electrical nerve stimulation (TENS) was applied over the index finger with instructions of its detrimental effects on force. To condition the subjects, the visual feedback on their force level was surreptitiously reduced after TENS. Results showed that the experimental group reduced the force, felt weaker and expected a worse performance than the control group, who was not suggested about TENS. By applying transcranial magnetic stimulation over the primary motor cortex, we found that while MEP amplitude remained stable throughout the procedure in both groups, the CSP duration was shorter in the experimental group after the nocebo procedure. The CSP reduction resembled previous findings on the placebo effect, suggesting that expectation of change in performance diminishes the inhibitory activation of the primary motor cortex, independently of the behavioural outcome.

Clinical and 22-item Sino-Nasal Outcome Test symptom patterns in primary headache disorder patients presenting to otolaryngologists with "sinus" headaches, pain or pressure

BACKGROUND

The objective of this work was to study patient and 22-item Sino-Nasal Outcome Test (SNOT-22) characteristics in primary headache disorders (PHDs).

METHODS

Retrospective chart review of "sinus" headache/pressure/pain patients was conducted. Patients that had rhinosinusitis excluded (negative endoscopy/computed tomography [CT]), and neurologist-confirmed PHD were studied. Patterns in symptom and SNOT-22 items were analyzed by network visualization and cluster analysis.

RESULTS

Forty-six patients met study criteria. Forty-three (93.5%) reported "need to blow nose" and 40 (86.9%) reported postnasal drainage. Sneezing was reported by 37 (80.4%) patients, "blockage/congestion of nose" by 33 (71.8%), and "runny nose by 32 (69.6%) patients. The median SNOT-22 score was 54 (interquartile range [IQR], 40 to 63). Past history included neurological diagnoses (60%), rhinologic disease (39%; chronic rhinosinusitis [CRS], rhinitis, recurrent acute sinusitis), asthma (28%), and allergen-sensitivity (26%). Previous sinonasal surgery had been performed in 41%. Network layout and cluster analysis identified 2 patient clusters and 2 symptom clusters. Two-thirds (31) of patients formed a tight cluster (cluster 1) linking to a symptom cluster of psychosocial items wrapped tightly with "facial pain/pressure." The remaining one-third of patients (cluster 2) linked to rhinologic symptoms loosely grouped away from "facial pressure/pain." In contrast to patients in cluster 2, patients in cluster 1 were predominantly female (p < 0.04), had significantly higher (p < 0.0001) median SNOT-22 scores (60 vs 34; IQR, 53 to 67 vs 17 to 42), were more likely to have migraine history (p = 0.058), and reported being "sad" (p < 0.0001) or "embarrassed" (p < 0.006).

CONCLUSION

Prominent rhinologic symptoms can be present in PHD patients in the absence of rhinosinusitis. In particular, high symptom-burden/SNOT-22 scores and high psychosocial symptoms should raise suspicion of PHD when endoscopy and/or CT results do not correlate with symptoms.

Placebo eff ects in psychiatry: mediators and moderators

A strong placebo response in psychiatric disorders has been noted for the past 50 years and various attempts have been made to identify predictors of it, by use of meta-analyses of randomised controlled trials and laboratory studies. We reviewed 31 meta-analyses and systematic reviews of more than 500 randomised placebo-controlled trials across psychiatry (depression, schizophrenia, mania, attention-deficit hyperactivity disorder, autism, psychosis, binge-eating disorder, and addiction) for factors identified to be associated with increased placebo response. Of 20 factors discussed, only three were often linked to high placebo responses: low baseline severity of symptoms, more recent trials, and unbalanced randomisation (more patients randomly assigned to drug than placebo). Randomised controlled trials in non-drug therapy have not added further predictors, and laboratory studies with psychological, brain, and genetic approaches have not been successful in identifying predictors of placebo responses. This comprehensive Review suggests that predictors of the placebo response are still to be discovered, the response probably has more than one mediator, and that different and distinct moderators are probably what cause the placebo response within psychiatry and beyond.

Placebo and nocebo effects in the neurological practice

Knowledge of placebo and nocebo effects is essential to identify their influence on the results in clinical practice and clinical trials, and thereby properly interpret their results. It is known that the gold standard of clinical trials research is the double-blind, placebo-controlled, randomized clinical study. The objective of this review is to distinguish specific from non-specific effects, so that the presence of positive effects in the group that received placebo (placebo effect) and the presence of adverse effects in the group receiving placebo (nocebo effect) lead to confounding in interpreting the results. Placebo and nocebo effects have been considered in neurological diseases such as depression, pain, headache, multiple sclerosis, epilepsy. As placebo and nocebo effects are also present in clinical practice, the purpose of this review is to draw attention to their influence on neurological practice, calling attention to the development of measures that can minimize them.

Dental fear in children: the role of previous negative dental experiences

OBJECTIVES

The aims of this study were to determine the potential main sources of anxiety in children visiting the dental office and to examine whether negative experiences influence the development of dental fear.

METHODS

Six hundred six subjects from the same pediatric dental office were consecutively invited to participate in the study (303 children/303 parents). An adapted version of the Wong-Baker FACES Pain Rating Scale and Corah's Dental Anxiety Scale were used to rate anxiety in children and parents. Clinical variables were collected by the same experienced pediatric dentist, with a view to determining their potential influence upon the development of fears. Descriptive statistics (mean, standard deviation), along with the Mann-Whitney U test, were used to determine the association between clinical variables and anxiety levels. Correlations were established using the Spearman coefficient (r) (p < 0.05).

RESULTS

No statistical differences were observed in anxiety levels with respect to patient gender (p > 0.05). Greater anxiety levels were observed in 4- and 5-year-old children (n = 56/55, respectively), with a negative correlation between age and anxiety level (r = -0.176; p = 0.002) and between parent anxiety level and patient age (r = -0.154; p = 0.007). A strong positive correlation was found between the anxiety levels of the parents and children (r = 0.954; p < 0.001). In addition, a moderate positive correlation was found between elevated anxiety levels in children (r = 0.381; p < 0.001) and parents (r = 0.454; p < .001) and the number of previous treatments in other dental offices.

CONCLUSIONS

Dental fear in children is strongly associated with inadequate dental management, causing anxiety levels to increase in both the children and parents.