Functional Movement Disorders and Placebo: A Brief Review of the Placebo Effect in Movement Disorders and Ethical Considerations for Placebo Therapy

The Social Epistemology of Clinical Placebos

Many extant theories of placebo focus on their causal structure wherein placebo effects are those that originate from select features of the therapy (e.g., client expectations or "incidental" features like size and shape). Although such accounts can distinguish placebos from standard medical treatments, they cannot distinguish placebos from everyday occurrences, for example, when positive feedback improves our performance on a task. Providing a social-epistemological account of a treatment context can rule out such occurrences, and furthermore reveal a new way to distinguish clinical placebos from standard medical treatments.

Longitudinal Meta-Analysis of Historical Parkinson's Disease Trials to Inform Future Trial Design

BACKGROUND

The outcome of clinical trials in neurodegeneration can be highly uncertain due to the presence of a strong placebo effect.

OBJECTIVES

To develop a longitudinal model that can enhance the success of future Parkinson's disease trials by quantifying trial-to-trial variations in placebo and active treatment response.

METHODS

A longitudinal model-based meta-analysis was conducted on the total score of Unified Parkinson's Disease Rating Scale (UPDRS) Parts 1, 2, and 3. The analysis included aggregate data from 66 arms (observational [4], placebo [28], or investigational-drug-treated [34]) from 4 observational studies and 17 interventional trials. Inter-study variabilities in key parameters were estimated. Residual variability was weighted by the size of study arms.

RESULTS

The baseline total UPDRS was estimated to average at 24.5 points. Disease score was estimated to worsen by 3.90 points/year for the duration of the treatments; whilst notably, arms with a lower baseline progressed faster. The model captured the transient nature of the placebo response and sustained symptomatic drug effect. Both placebo and drug effects peaked within 2 months; although, 1 year was needed to observe the full treatment difference. Across these studies, the progression rate varied by 59.4%, the half-life for offset of placebo response varied by 79.4%, and the amplitude for drug effect varied by 105.3%.

CONCLUSION

The longitudinal model-based meta-analysis describes UPDRS progression rate, captures the dynamics of the placebo response, quantifies the effect size of the available therapies, and sets the expectation of uncertainty for future trials. The findings provide informative priors to enhance the rigor and success of future trials of promising agents, including potential disease modifiers. © 2023 GSK. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Functional neurological disorder and placebo and nocebo effects: shared mechanisms

Functional neurological disorder (FND) is characterized by neurological symptoms that cannot be explained by a structural neurological cause. Among the different aetiological models that have been proposed for FND, of note is the Bayesian predictive coding model, which posits that perception relies on top-down cortical predictions (priors) to infer the source of incoming sensory information. This model can also apply to non-pathological experiences, such as placebo and nocebo effects, wherein sensory information is shaped by prior expectations and learning. To date, most studies of the relationship between placebo and nocebo effects and FND have focused on the use of placebos for diagnosis and treatment of FND. Here, we propose that this relationship might go beyond diagnosis and therapy. We develop a framework in which shared cognitive, personality and neuroanatomical factors justify the consideration of a deeper link between FND and placebo and nocebo effects. This new perspective might offer guidance for clarification of the pathogenesis of FND and for the identification of potential biomarkers and therapeutic targets.

Psychedelic-assisted therapy for functional neurological disorders: A theoretical framework and review of prior reports

Functional neurological disorders (FNDs), which are sometimes also referred to as psychogenic neurological disorders or conversion disorder, are common disabling neuropsychiatric disorders with limited treatment options. FNDs can present with sensory and/or motor symptoms, and, though they may mimic other neurological conditions, they are thought to occur via mechanisms other than those related to identifiable structural neuropathology and, in many cases, appear to be triggered and sustained by recognizable psychological factors. There is intriguing preliminary evidence to support the use of psychedelic‐assisted therapy in a growing number of psychiatric illnesses, including FNDs. We review the theoretical arguments for and against exploring psychedelic‐assisted therapy as a treatment for FNDs. We also provide an in‐depth discussion of prior published cases detailing the use of psychedelics for psychosomatic conditions, analyzing therapeutic outcomes from a contemporary neuroscientific vantage as informed by several recent neuroimaging studies on psychedelics and FNDs.

Treatment of functional neurological disorder: current state, future directions, and a research agenda

Functional neurological disorder (FND) encompasses a complex and heterogeneous group of neuropsychiatric syndromes commonly encountered in clinical practice. Patients with FND may present with a myriad of neurological symptoms and frequently have comorbid medical, neurological, and psychiatric disorders. Over the past decade, important advances have been made in understanding the pathophysiology of FND within a biopsychosocial framework. Many challenges remain in addressing the stigma associated with this diagnosis, refining diagnostic criteria, and providing access to evidence-based treatments. This paper outlines FND treatment approaches, emphasizing the importance of respectful communication and comprehensive explanation of the diagnosis to patients, as critical first step to enhance engagement, adherence, self-agency, and treatment outcomes. We then focus on a brief review of evidence-based treatments for psychogenic non-epileptic seizures and functional movement disorder, a guide for designing future treatment trials for FND, and a proposal for a treatment research agenda, in order to aid in advancing the field to develop and implement treatments for patients with FND.

Estimating contextual effect in nonpharmacological therapies for pain in knee osteoarthritis: a systematic analytic review

OBJECTIVE

Conduct a systematic review and use meta-analytic techniques to estimate the proportion of total treatment effect that can be attributable to contextual effects (PCE) in adults receiving nonpharmacological, nonsurgical (NPNS) treatments for knee osteoarthritis (OA).

DESIGN

We reviewed the published literature to identify five frequently studied NPNS treatments for knee OA: exercise, acupuncture, ultrasound, laser, and transcutaneous electrical nerve stimulation (TENS). We searched for randomized controlled trials (RCTs) of these treatments and abstracted pre- and post-intervention pain scores for groups receiving placebo and active treatments. For each study we calculated the PCE by dividing the change in pain in the placebo group by the change in pain in the active treatment group. We log transformed the PCE measure and pooled across studies using a random effects model.

RESULTS

We identified 25 studies for analysis and clustered the RCTs into two groups: acupuncture and topical energy modalities (TEM). 13 acupuncture studies included 1,653 subjects and 12 TEM studies included 572 subjects. The combined PCE was 0.61 (95% CI 0.46-0.80) for acupuncture and 0.69 (95% CI 0.54-0.88) for TEM.

CONCLUSION

Our findings suggest that about 61% and 69% of the total treatment effect experienced by subjects receiving acupuncture and TEM treatments, respectively, for knee OA pain may be explained by contextual effects. Contextual effects may include the placebo effect, changes attributable to natural history, and effects of co-therapies. These data highlight the important role of contextual effects in the response to NPNS OA treatments.

[Functional movement disorders in children and adolescents]

Functional movement disorders (FMDs), also known as psychogenic movement disorders (PMDs), should be considered a biological-psychological-social disease like other functional neurological diseases. It is not merely a psychological or mental disease. The etiology of FMDs includes neurobiological changes, such as abnormal patterns of cerebral activation and abnormal connectivity between the limbic system and the motor networks. Inheritance and epigenetic machinery, such as DNA methylation and changes in grey and white matter morphology, may influence the development of FMDs. FMDs are not rare in the outpatient service of pediatrics and are one of the most challenging movement disorders due to complex and diversified clinical manifestations. Due to a lack of clinical knowledge and unified diagnostic criteria, it is difficult for pediatricians to make a correct diagnosis of FMDs, which may be easily confused with other diseases. Pediatricians should pay more attention to children with FMDs and establish a multidisciplinary team with psychiatrists, specialists in developmental behavior, and physiotherapists, so as to provide active management and treatment for such children.