Learning by observing: a systematic exploration of modulatory factors and the impact of observationally induced placebo and nocebo effects on treatment outcomes

Introduction

Observational learning (OL) refers to learning through observing other people's behavior. OL has been suggested as an effective and simple tool to evoke treatment expectations and corresponding placebo and nocebo effects. However, the exact mechanisms by which OL shapes treatment outcomes, its moderating factors and possible areas of application remain unclear. We thus reviewed the existing literature with two different literature searches to answer the following questions: Which influencing factors contribute to OL-induced placebo and nocebo effects (in healthy volunteers and patients) and how large are these effects (search 1)? In which medical fields has OL been used so far to modulate treatment expectancy and treatment outcomes in patients, their caregivers, and at-risk groups (search 2)? We also aimed to explore whether and how the assessment of treatment expectations has been incorporated.

Methods

We conducted two independent and comprehensive systematic literature searches, both carried out on September 20, 2022.

Results

We identified 21 studies that investigated OL-mediated placebo and nocebo effects for pain and itch, the (placebo) efficacy of sham treatment on anxiety, and the (nocebo) induction of medication side effects (search 1). Studies showed that OL can efficiently induce placebo and nocebo effects across different presentation modes, with medium effect sizes on average: placebo effects, d = 0.79 (range: d = -0.36-1.58), nocebo effects, d = 0.61 (range: d = 0.04-1.5). Although several moderating factors have been investigated, their contribution to OL-induced effects remains unclear because of inconsistent results. Treatment expectation was assessed in only four studies. Regarding medical applications of OL (search 2), we found 12 studies. They showed that OL was effectively applied in preventive, therapeutic and rehabilitative interventions and that it was mainly used in the field of psychosomatics.

Discussion

OL effects on treatment outcomes can be both positive and negative. Future research should investigate which individuals would benefit most from OL and how OL can be implemented most effectively to induce placebo and avoid nocebo effects in clinical settings.

Systematic review registration

This work was preregistered at the Center for Open Science as open-ended registration (doi: 10.17605/OSF.IO/FVHKE). The protocol can be found here: https://archive.org/details/osf-registrations-fvhke-v1.

Translating knowledge on placebo and nocebo effects into clinical practice

Introduction

Positive and negative treatment expectations are powerful modulators of health and treatment outcomes. A substantial part of treatment success is due to contextual factors modulating patient's expectations towards a treatment. Consequently, treatment expectations should be a target of therapeutic interventions themselves.

Objectives

This article highlights the neurobiological underpinnings of treatment expectations as well as strategies to modulate contextual factors to optimize treatment outcomes in daily clinical settings.

Methods

This clinical update aligns with the 2022 IASP Global Year Translating Pain Knowledge into Practice and selectively reviews the best available evidence and practice.

Results

The effects of treatment expectations, also known as placebo and nocebo effects, are observed in various clinical conditions and physiological systems. However, most of our knowledge comes from the field of pain, where expectation effects substantially contribute to overall analgesic treatment outcomes. Experimental placebo analgesia paradigms provide the best illustration of how analgesic effects can be attributed not only to a pharmacological or specific treatment, but instead are the result of the expectation towards the treatment. The impact of expectations on treatment outcome is highly variable between individuals, and the identification of factors predicting an individual's response has proven to be challenging. Further research is required to provide personalized treatment strategies for the daily clinical practice.

Conclusion

Patient's previous experiences and expectations are powerful modulators of treatment efficacy, tolerability, and adherence. By providing a comprehensive overview of recent advances in this field, this review offers valuable insights for clinicians and researchers seeking to improve patient-clinician interaction.

Study protocol: effects of treatment expectation toward repetitive transcranial magnetic stimulation (rTMS) in major depressive disorder-a randomized controlled clinical trial

BACKGROUND

Patients' expectations toward any given treatment are highly important for the effectiveness of such treatment, as has been demonstrated for several disorders. In particular, in major depressive disorder (MDD), one of the most frequent and most serious mental disorders with severe consequences for the affected, the augmentation of available treatment options could mean a ground-breaking success. Repetitive transcranial magnetic stimulation (rTMS), a new, non-invasive, and well-tolerated intervention with proven effects in the treatment of MDD, appears particularly suitable in this context as it is assumed to exert its effect via structures implicated in networks relevant for both expectation and depression.

METHODS

All patients will receive rTMS according to its approval. Half of the patients will be randomized to a psychological intervention, which is a comprehensive medical consultation aiming to improve positive treatment expectations; the control group will receive a conventional informed consent discussion (in the sense of a treatment-as-usual condition). As outcome parameters, instruments for both self-assessment and external assessment of depression symptoms will be applied. Furthermore, psycho-immunological parameters such as inflammation markers and the cortisol awakening response in saliva will be investigated. Resting-state functional magnetic resonance imaging (rs fMRI) will be performed to analyze functional connectivity, including the cerebellum, and to identify neuronal predictors of expectation effects. In addition, possible cerebellar involvement will be assessed based on a cerebellar-dependent motor learning paradigm (i.e., eyeblink conditioning).

DISCUSSION

In this study, the effects of treatment expectations towards rTMS are investigated in patients with MDD. The aim of this study is to identify the mechanisms underlying the expectation effects and, beyond that, to expand the potential of non-invasive and well-tolerated treatments of MDD.

TRIAL REGISTRATION

German Registry of Clinical Studies (DRKS DRKS00028017. Registered on 2022/03/07. URL: https://www.drks.de/drks_web/ .

[Placebo effects in analgesia : Influence of expectations on the efficacy and tolerability of analgesic treatment]

Expectations of patients influence the perception and neuronal processing of acute and chronic pain and modulate the effectiveness of analgesic treatment. The expectation of treatment is not only the most important determinant of placebo analgesia. Expectations of treatment also influence the efficacy and tolerability of "active" pharmacological and non-pharmacological treatment of pain. Recent insights into the psychological and neurobiological mechanisms underlying the clinically relevant effects of treatment expectations enable and call for the systematic integration and modulation of treatment expectations into analgesic treatment concepts. Such a strategy promises to optimize analgesic treatment and to prevent or reduce the burden of unwanted side effects and the misuse of analgesics, particularly of opioids. This review highlights the current concepts, recent achievements and also challenges and key open research questions.

[Neurobiological and neurochemical mechanisms of placebo analgesia]

BACKGROUND

The efficacy of pain therapies can be substantially modulated by treatment expectations, which is reflected by the substantial placebo effects observed in pain (so called placebo analgesia).

QUESTION

What is currently known about the neurobiological and neurochemical mechanisms underlying placebo analgesia?

MATERIALS AND METHODS

A focused presentation of key publications in the field embedded in a structured overview of the mechanistic concepts and current theories according to recent evidence.

RESULTS

Experimental studies with functional neuroimaging showed that the effect of placebo analgesia is reflected by changes in brain activity related to pain processing and cognitive control. The important neurotransmitters involved include opioids and dopamine.

CONCLUSION

Placebo analgesia is associated with complex neurobiological and -physiological mechanisms. An advanced comprehension of these processes should be applied to optimize existing and future therapeutic approaches in pain therapy.

Online processing of moral transgressions: ERP evidence for spontaneous evaluation

Experimental studies using fictional moral dilemmas indicate that both automatic emotional processes and controlled cognitive processes contribute to moral judgments. However, not much is known about how people process socio-normative violations that are more common to their everyday life nor the time-course of these processes. Thus, we recorded participants' electrical brain activity while they were reading vignettes that either contained morally acceptable vs unacceptable information or text materials that contained information which was either consistent or inconsistent with their general world knowledge. A first event-related brain potential (ERP) positivity peaking at ∼200 ms after critical word onset (P200) was larger when this word involved a socio-normative or knowledge-based violation. Subsequently, knowledge-inconsistent words triggered a larger centroparietal ERP negativity at ∼320 ms (N400), indicating an influence on meaning construction. In contrast, a larger ERP positivity (larger late positivity), which also started at ∼320 ms after critical word onset, was elicited by morally unacceptable compared with acceptable words. We take this ERP positivity to reflect an implicit evaluative (good-bad) categorization process that is engaged during the online processing of moral transgressions.

Reduced magnetisation transfer ratio in cognitively impaired patients at the very early stage of multiple sclerosis: a prospective, multicenter, cross-sectional study

OBJECTIVES

Cognitive impairment belongs to the core symptoms in multiple sclerosis (MS) and can already be present at the very early stages of the disease. The present study evaluated cognitive functioning after the first clinical presentation suggestive of MS and brain tissue damage in a non-lesion focused MRI approach by using magnetisation transfer imaging (MTI).

SETTING AND PARTICIPANTS

47 patients (15 men and 32 women; mean age: 31.17 years) after the first clinical event suggestive of MS were recruited in six different MS centres in Germany and underwent a neuropsychological test battery including tests for attention, memory and executive function as well as depression and fatigue. MTI and conventional MRI measures (T1/T2 lesion load) were assessed. In addition, Magnetisation Transfer Ratio (MTR) maps were calculated. Primary outcome measure was the investigation of cognitive dysfunction in very early MS in correlation to MRI data.

RESULTS

55.3% of patients with MS failed at least one test parameter. Specifically, 6% were reduced in working memory, 14.9% in focused attention, 25.5% in figural learning and up to 14.9% in executive function. When the sample was subdivided into cognitively impaired and preserved, MTR scores within the cognitively impaired subgroup were significantly lower compared with the preserved group (t(43)=2.346, p=0.02*). No significant differences between the two groups were found in T2-weighted and T1-weighted lesion volume.

CONCLUSIONS

After the first MS-related clinical event, 55.3% of patients showed distinct cognitive deficits. Cognitively impaired patients had significantly lower whole brain MTR, but no differences in focal brain lesion volumes supporting the idea that early cognitive deficits may be related to diffuse loss of brain tissue integrity.

Steady-state movement-related potentials evoked by fast repetitive movements

We investigated steady-state movement-related cortical potentials elicited by fast repetitive movements (1/sec) with 50-channel EEG. The experimental design comprised a comparison (a) between unilateral movements of the digits and the toes and (b) between metronome-paced and self-paced initiation of the movements. A distinct biphasic pattern of electrical activity following movement onset was observed, namely a frontal negative peak at a latency of 90 ms (post-MP100) anda frontal positive peak at a latency of 310ms (post-MP300). Pacing exerted its effects mainly on the amplitude and on the latency of the post-MP300. Source analysis revealed that both peaks could be modelled by a single source. The source locations were highly reproducible across the metronome-paced and self-paced conditions, and, they followed the expected somatotopic organisation.

Micellar electrokinetic capillary chromatography as a powerful tool for pharmacological investigations without sample pretreatment: a precise technique providing cost advantages and limits of detection to the low nanomolar range

A number of pharmaceuticals (e.g., acetaminophen, salicylic acid, sulfamethoxazole, theophylline, tolbutamide and trimethoprim) have been determined in human plasma by micellar electrokinetic chromatography (MEKC), without sample pretreatment, using underivatized fused-silica capillaries. The total analysis time was only 10 min. A sodium dodecyl sulfate (SDS)-containing borate buffer (60 mM with 200 mM SDS) at pH 10 was used. Between runs, proteins adsorbed to the capillary wall are removed by rinsing with SDS buffer and either acetonitrile (e.g., 50% v/v) or isopropanol (e.g., 10% v/v). Other rinsing procedures are discussed (salts, enzyme-containing solutions, organic solvents, sodium hydroxide, hydrofluoric acid). The separation system is tested in a concentration range between 10 ng/mL and 100 microg/mL; a detection limit of about 20 ng/mL can readily be obtained. The sensitivity was substantially improved using isopropanol as buffer additive. A day-to-day precision for relative peak areas of 1-2% relative standard deviation (RSD, n > 40) was reached in the upper concentration range. Under repeatability conditions, these values could also be obtained for low microg/mL concentrations. Thus, not only drug monitoring but also pharmacokinetic investigations from blood plasma become possible without further sample pretreatment.

Constraint-induced movement therapy for motor recovery in chronic stroke patients

OBJECTIVE

Assessment of the effectiveness of constraint-induced (CI) movement therapy and quantitative evaluation of the effects of CI therapy.

DESIGN

Intervention study; case series; pretreatment to posttreatment measures and follow-up 3 months after intervention.

SETTING

An outpatient department.

PATIENTS

Five chronic stroke patients with moderate motor deficit; convenience sample.

INTERVENTIONS

CI therapy consisting of restraint of the unaffected upper extremity in a sling for 14 days combined with 6 hours of training per weekday of the affected upper extremity.

MAIN OUTCOME MEASURES

Actual Amount of Use Test (AAUT), Motor Activity Log (MAL), Wolf Motor Function Test (WMFT), and Arm Motor Ability Test (AMAT) RESULTS: There was a substantial improvement in the performance times of the laboratory tests (AMAT, WMFT, p < or = .039) and in the quality of movement (AMAT, WMFT, p < or = .049; MAL, p = .049), particularly in the use of the extremity in "real world" environments (AAUT, p = .020), supported by results of quantitative evaluation. The effect sizes were large and comparable to those found in previous studies of CI therapy.

CONCLUSIONS

CI therapy is an efficacious treatment for chronic stroke patients, especially in terms of real world outcome.

Pharmacokinetic investigations with direct injection of plasma samples: possible savings using capillary electrophoresis (CE)

Capillary electrophoresis (CE) is often regarded as a separation technique of choice because of its high selectivity and its cost advantages compared to LC.RSD% of 0.5% have become standard for quality control assays. Using CE, sample pretreatment can often be significantly reduced, leading to notable savings of labor and reagent costs. Moreover, errors from sample pretreatment steps are avoided. A number of pharmaceuticals (e.g. acetaminophen, salicylic acid, sulfamethoxazole, theophylline, tolbutamide, and trimethoprim) have been determined in human plasma on underivatized fused silica capillaries by MEKC without sample pretreatment, the total analysis time being only 10 min. An sodium dodecyl sulfate-containing borate buffer (60 mM with 200 mM SDS) at pH 10 has been used. Between runs, proteins adsorbed to the capillary wall are removed by a rinsing regimen consisting of SDS buffer and either acetonitrile (e.g. 50% v/v) or isopropanol (e.g. 10% v/v). Other rinsing approaches are discussed (salts, enzyme containing solutions, organic solvents, sodium hydroxide, hydrofluoric acid). The separation system is tested in a concentration range between 10 ng/mL and 100 micrograms/mL, the detection limit being about 5 ng/mL. The sensitivity has been substantially improved compared to preceding work using field-amplified injection mechanisms and efficient computer algorithms that take advantage of multiwavelength detection. Correlations between the limit of quantitation (LOQ), the limit of detection (LOD) and the signal/noise ratio are discussed. A day-to-day precision for relative peak areas of 1 to 2% relsdv (n > 40) has been reached in the upper concentration range. Thus, not only drug monitoring but also pharmacokinetic investigations from blood plasma have become possible without further sample pretreatment.

Plasticity in the motor system related to therapy-induced improvement of movement after stroke

Neuroplasticity might play a beneficial role in the recovery of function after stroke but empirical evidence for this is lacking thus far. Constraint-induced (CI) therapy was used to increase the use of a paretic upper extremity in four hemiparetic stroke patients. Dipole modeling of steady-state movement-related cortical potentials was applied before and after training and 3 months later. The source locations associated with affected hand movement were unusual at follow-up because activation of the ipsilateral hemisphere was found in the absence of mirror movements of the unaffected hand. This long-term change may be considered as an initial demonstration of large-scale neuroplasticity associated with increased use of the paretic limb after application of CI therapy.

Strategies for capillary electrophoresis: method development and validation for pharmaceutical and biological applications

This review is in support of the development of selective, reproducible and validated capillary electrophoretis (CE) methods. Focusing on pharmaceutical and biological applications, the successful use of CE is demonstrated by more than 800 references, mainly from 1994 until 1998. Approximately 80 recent reviews have been catalogued. These articles sum up the existing strategies for method development in CE, especially in the search for generally accepted concepts, but also looking for new, promising reagents and ideas. General strategies for method development were derived not only with regard to selectivity and efficiency, but also with regard to precision, short analysis time, limit of detection, sample pretreatment requirements and validation. Standard buffer recipes, surfactants used in micellar electrokinetic capillary chromatography (MEKC), chiral selectors, useful buffer additives, polymeric separation media, electroosmotic flow (EOF) modifiers, dynamic and permanent coatings, actions to deal with complex matrices and aspects of validation are collected in 20 tables. Detailed schemes for the development of MEKC methods and chiral separations, for optimizing separation efficiency, means of troubleshooting, and other important information for key decisions during method development are given in 19 diagrams. Method development for peptide and protein separations, possibilities to influence the EOF and how to stabilize it, as well as indirect detection are considered in special sections.

Determination of pharmaceuticals in plasma by capillary electrophoresis without sample pretreatment reproducibility, limit of quantitation and limit of detection

Pharmaceuticals in human plasma are determined on underivatized fused-silica capillaries by micellar electrokinetic capillary chromatography (MEKC) without sample pretreatment. Our best method to date uses as running buffer a sodium dodecyl sulfate (SDS) containing borate buffer (60 mM with 200 mM SDS) at pH 10. Between runs, proteins adsorbed to the capillary wall are removed by an acetonitrile and SDS-buffer rinsing regimen (50% v/v each). A day-to-day precision for relative peak areas of about 2% relative standard deviation (RSD; n > 40) has been reached. Different rinsing approaches are discussed (salts, enzyme-containing solutions, organic solvents, hydrofluoric acid). The separation system is tested in a concentration range between approximately 100 mg/L-10 mg/L. Correlations between the limit of quantitation, the limit of detection and the signal/noise are discussed. The applicability of the system is demonstrated for the pharmaceuticals acetaminophen, salicylic acid, sulfamethoxazole, tolbutamide, and trimethoprim.

The Arm Motor Ability Test: reliability, validity, and sensitivity to change of an instrument for assessing disabilities in activities of daily living

OBJECTIVE

To continue and expand determination of the reliability, validity, and sensitivity to change of the Arm Motor Ability Test (AMAT), an instrument for assessing deficits in activities of daily living (ADL).

DESIGN

The AMAT was administered twice to patients, with an interest interval of either 1 or 2 weeks, by one of two examiners assigned to patients in counterbalanced order. Patients' interest intervals and scores on the arm portion of the Motricity Index was unknown to the raters.

SETTING

A referral inpatient neurological rehabilitation center.

PATIENTS

Thirty-three subacute stroke inpatients with moderate to mild upper extremity motor deficit: median Motricity-Index-Arm score = 89, median chronicity = 43d, median age = 66yr; 12 were women.

MAIN OUTCOME MEASURE AND RESULTS

The AMAT was developed in 1987, and interrater reliabilities at that time were found to range from .95 to .99. The present values for interrater reliability (2 scales) from videotaped test performance were: kappas = .68 to .77. Spearman correlations = .97 to .99. For performance time, interscorer reliability from videotaped test performance was .99. Homogeneities for the three AMAT measures for the total sample (Cronbach's alpha and split-half reliability) were .93 to .99. The test-retest reliabilities for the total sample were .93 to .99. The correlations to the Motricity-Index-Arm score were .45 to .61. The AMAT detected the difference in change occurring as a result of the passage of 1 versus 2 weeks in these subacute inpatients, presumably as a result of intensive therapy and/or spontaneous recovery, confirming the results of an earlier intervention study.

CONCLUSION

The AMAT is an instrument with high interrater reliability, internal consistency, and sensitivity to change, as well as having satisfactory concurrent validity.

Quantitation of acetaminophen and salicylic acid in plasma using capillary electrophoresis without sample pretreatment. Improvement of precision

Capillary electrophoresis has become one of the most attractive techniques in the analysis of biological samples. Pharmaceuticals in human plasma can easily be determined on uncoated fused-silica capillaries without any sample pretreatment. Intra- and inter-day precision values of about 1-2% R.S.D. (n = 20) and 2-3% R.S.D. (n > 80) respectively are obtained using a sodium dodecyl sulfate-containing borate buffer, pH 10 and acetonitrile as a between-run rinsing reagent. This method is highly robust, no breakdowns of the current or capillary blockings were observed for several weeks. The general applicability is demonstrated for several model drugs. The effectiveness of other rinsing procedures including enzyme-containing solutions, different organic solvents and hydrofluoric acid is discussed.

Spinal compensation for postural deficits after hemilabyrinthectomy?

Removal of the labyrinthine organs on one side results in static and dynamic disturbances. Some functional recovery occurs over time and is paralleled in frogs by an increase in the efficacy of central vestibular pathways. Here, we report concomitant increases in dorsal root evoked ventral root responses in the brachial spinal cord and compare the time courses of neural changes in the brain stem and in the spinal cord with the progress of postural recovery in frogs. From this comparison we conclude that postural deficits are compensated by a spinal substitution process on the operated side.

[Sympathetic trunk treatment or infusion therapy in cases of sudden deafness (author's transl)]

The optimal criterion for registering the result of a sudden-deafness-therapy is a class interval of 25 dB in the audiogram, followed by punctal evaluation of the mean value of the frequencies 0,5/1/2/4/8 kc/sec. Blocking of the sympathetic trunk, as well as infusions using low-molecular dextranes or derivatives of nicotnic acid, furthermore strictly oral treatment as well as combinations of all these, all lead to a statistically proved recovery of hearing. The extent of improvement is ascertainbly smaller with strictly oral treatment than with blocking the sympathetic trunk or with infusions. Hearing is slightly more improved by blocking the sympathetic trunk than by infusional treatment. Statistically however, the difference is not significant. Low-molecular dextran (Rheomakrodex) is not superior to Xantinol-Nicotinate (Complamin). Future investigations in the assessment of therapeutical results should exclusively evaluate unilateral sudden deafness and include the intact second ear into the computation.