Greater baseline pain inclusion criteria in clinical trials increase regression to the mean effect: a modelling study

Counting your chickens before they hatch: improvements in an untreated chronic pain population, beyond regression to the mean and the placebo effect

Introduction

Isolating the effect of an intervention from the natural course and fluctuations of a condition is a challenge in any clinical trial, particularly in the field of pain. Regression to the mean (RTM) may explain some of these observed fluctuations.

Objectives

In this paper, we describe and quantify the natural trajectory of questionnaire scores over time, based on initial scores.

Methods

Twenty-seven untreated chronic low back pain patients and 25 healthy controls took part in this observational study, wherein they were asked to complete an array of questionnaires commonly used in pain studies during each of 3 visits (V1, V2, V3) at the 2-month interval. Scores at V1 were classified into 3 subgroups (extremely high, normal, and extremely low), based on z-scores. The average delta (∆ = V2 - V1) was calculated for each subgroup, for each questionnaire, to describe the evolution of scores over time based on initial scores. This analysis was repeated with the data for V2 and V3.

Results

Our results show that high initial scores were widely followed by more average scores, while low initial scores tended to be followed by similar (low) scores.

Conclusion

These trajectories cannot be attributable to RTM alone because of their asymmetry, nor to the placebo effect as they occurred in the absence of any intervention. However, they could be the result of an Effect of Care, wherein participants had meaningful improvements simply from taking part in a study. The improvement observed in patients with high initial scores should be carefully taken into account when interpreting results from clinical trials.

From cause and effect to causes and effects

It is now-at least loosely-acknowledged that most health and clinical outcomes are influenced by different interacting causes. Surprisingly, medical research studies are nearly universally designed to study-usually in a binary way-the effect of a single cause. Recent experiences during the coronavirus disease 2019 pandemic brought to the forefront that most of our challenges in medicine and healthcare deal with systemic, that is, interdependent and interconnected problems. Understanding these problems defy simplistic dichotomous research methodologies. These insights demand a shift in our thinking from 'cause and effect' to 'causes and effects' since this transcends the classical way of Cartesian reductionist thinking. We require a shift to a 'causes and effects' frame so we can choose the research methodology that reflects the relationships between variables of interest-one-to-one, one-to-many, many-to-one or many-to-many. One-to-one (or cause and effect) relationships are amenable to the traditional randomized control trial design, while all others require systemic designs to understand 'causes and effects'. Researchers urgently need to re-evaluate their science models and embrace research designs that allow an exploration of the clinically obvious multiple 'causes and effects' on health and disease. Clinical examples highlight the application of various systemic research methodologies and demonstrate how 'causes and effects' explain the heterogeneity of clinical outcomes. This shift in scientific thinking will allow us to find the necessary personalized or precise clinical interventions that address the underlying reasons for the variability of clinical outcomes and will contribute to greater health equity.

Emerging drugs for the treatment of irritability associated with autism spectrum disorder

INTRODUCTION

Autism spectrum disorder (ASD) is an early-onset disorder with a prevalence of 1% among children and reported disability-adjusted life years of 4.31 million. Irritability is a challenging behavior associated with ASD, for which medication development has lagged. More specifically, pharmacotherapy effectiveness may be limited against high adverse effects (considering side effect profiles and patient medication sensitivity); thus, the possible benefits of pharmacological interventions must be balanced against potential adverse events in each patient.

AREAS COVERED

After reviewing the neuropathophysiology of ASD-associated irritability, the benefits and tolerability of emerging medications in its treatment based on randomized controlled trials were detailed in light of mechanisms and targets of action.

EXPERT OPINION

Succeeding risperidone and aripiprazole, monotherapy with memantine may be beneficial. In addition, N-acetylcysteine, galantamine, sulforaphane, celecoxib, palmitoylethanolamide, pentoxifylline, simvastatin, minocycline, amantadine, pregnenolone, prednisolone, riluzole, propentofylline, pioglitazone, and topiramate, all adjunct to risperidone, and clonidine and methylphenidate outperformed placebo. These effects were through glutamatergic, γ-aminobutyric acidergic, inflammatory, oxidative, cholinergic, dopaminergic, and serotonergic systems. All medications were reported to be safe and tolerable. Considering sample size, follow-up, and effect size, further studies are necessary. Along with drug development, repositioning and combining existing drugs supported by the mechanism of action is recommended.

Characterizing Acute Low Back Pain in a Community-Based Cohort

Acute low back pain (LBP) is a common experience, however, the associated pain severity, pain frequency, and characteristics of individuals with acute LBP in community settings have yet to be well understood. The purpose of this manuscript is to categorize and compare acute LBP groups for differences in the following characteristics: 1) sociodemographic, 2) general and physical health, and 3) psychological. This cross-sectional study used baseline data from 131 community-based participants with acute LBP (<4 weeks duration before screening and > 30 pain-free days before acute LBP onset). Two LBP categorization definitions were used based on LBP frequency combined with either: 1) pain interference frequency (impact-based) or 2) pain intensity (intensity-based). Descriptive associations were calculated as prevalence ratios for categorical variables and Hedges' g for continuous variables. Our analyses identified several large associations for impact-based and intensity-based categories for pain interference with activity and with enjoyment in life, global mental health, STarT Back Screening Tool risk category, general health, and Fear Avoidance Beliefs Questionnaire-Physical Activity subscale. Larger associations were found with social constructs (racially and ethnically minoritized, performance of social roles, and isolation) when using the intensity-based versus impact-based categorization. This study adds to the literature by providing standard ways to characterize community-based individuals experiencing acute LBP. The robust differences observed between these categorization approaches suggest they may be used to improve the early identification of factors potentially contributing to the development of chronic LBP.

Neuropsychological Function in Traumatic Brain Injury and the Influence of Chronic Pain

Cognitive dysfunction, pain, and psychological morbidity all present unique challenges to those living with traumatic brain injury (TBI). In this study we examined (a) the impact of pain across domains of attention, memory, and executive function, and (b) the relationships between pain and depression, anxiety, and post-traumatic stress disorder (PTSD) in persons with chronic TBI. Our sample included 86 participants with a TBI and chronic pain (n = 26), patients with TBI and no chronic pain (n = 23), and a pain-free control group without TBI (n = 37). Participants visited the laboratory and completed a comprehensive battery of neuropsychological tests as part of a structured interview. Multivariate analysis of covariance using education as a covariate, failed to detect a significant group difference for neuropsychological composite scores of attention, memory, and executive function (p = .165). A follow-up analysis using multiple one-way analysis of variance (ANOVA) was conducted for individual measures of executive function. Post-hoc testing indicated that those in both TBI groups preformed significantly worse on measures of semantic fluency when compared to controls (p < 0.001, ηρ2 = .16). Additionally, multiple ANOVAs indicated that those with TBI and pain scored significantly worse across all psychological assessments (p < .001). We also found significant associations between measures of pain and most psychological symptoms. A follow-up stepwise linear regression among those in the TBI pain group indicated that post concussive complaints, pain severity, and neuropathic pain symptoms differentially contributed to symptoms of depression, anxiety, and PTSD. These findings suggest deficits in verbal fluency among those living with chronic TBI, with results also reinforcing the multidimensional nature of pain and its psychological significance in this population.