Precision non-implantable neuromodulation therapies : a perspective for the depressed brain

Current first-line treatments for major depressive disorder (MDD) include pharmacotherapy and cognitive-behavioral therapy. However, one-third of depressed patients do not achieve remission after multiple medication trials, and psychotherapy can be costly and time-consuming. Although nonimplantable neuromodulation (NIN) techniques such as transcranial magnetic stimulation, transcranial direct current stimulation, electroconvulsive therapy, and magnetic seizure therapy are gaining momentum for treating MDD, the efficacy of non-convulsive techniques is still modest, whereas use of convulsive modalities is limited by their cognitive side effects. In this context, we propose that NIN techniques could benefit from a precision-oriented approach. In this review, we discuss the challenges and opportunities in implementing such a framework, focusing on enhancing NIN effects via a combination of individualized cognitive interventions, using closed-loop approaches, identifying multimodal biomarkers, using computer electric field modeling to guide targeting and quantify dosage, and using machine learning algorithms to integrate data collected at multiple biological levels and identify clinical responders. Though promising, this framework is currently limited, as previous studies have employed small samples and did not sufficiently explore pathophysiological mechanisms associated with NIN response and side effects. Moreover, cost-effectiveness analyses have not been performed. Nevertheless, further advancements in clinical trials of NIN could shift the field toward a more ‘‘precision-oriented’’ practice

Mega-analysis methods in ENIGMA : the experience of the generalized anxiety disorder working group

The ENIGMA group on Generalized Anxiety Disorder (ENIGMA-Anxiety/GAD) is part of a broader effort to investigate anxiety disorders using imaging and genetic data across multiple sites worldwide. The group is actively conducting a mega-analysis of a large number of brain structural scans. In this process, the group was confronted with many methodological challenges related to study planning and implementation, between-country transfer of subject-level data, quality control of a considerable amount of imaging data, and choices related to statistical methods and efficient use of resources. This report summarizes the background information and rationale for the various methodological decisions, as well as the approach taken to implement them. The goal is to document the approach and help guide other research groups working with large brain imaging data sets as they develop their own analytic pipelines for mega-analyses

Cortical and subcortical brain structure in generalized anxiety disorder : findings from 28 research sites in the ENIGMA-Anxiety Working Group

The goal of this study was to compare brain structure between individuals with generalized anxiety disorder (GAD) and healthy controls. Previous studies have generated inconsistent findings, possibly due to small sample sizes, or clinical/analytic heterogeneity. To address these concerns, we combined data from 28 research sites worldwide through the ENIGMA-Anxiety Working Group, using a single, pre-registered mega-analysis. Structural magnetic resonance imaging data from children and adults (5–90 years) were processed using FreeSurfer. The main analysis included the regional and vertex-wise cortical thickness, cortical surface area, and subcortical volume as dependent variables, and GAD, age, age-squared, sex, and their interactions as independent variables. Nuisance variables included IQ, years of education, medication use, comorbidities, and global brain measures. The main analysis (1020 individuals with GAD and 2999 healthy controls) included random slopes per site and random intercepts per scanner. A secondary analysis (1112 individuals with GAD and 3282 healthy controls) included fixed slopes and random intercepts per scanner with the same variables. The main analysis showed no effect of GAD on brain structure, nor interactions involving GAD, age, or sex. The secondary analysis showed increased volume in the right ventral diencephalon in male individuals with GAD compared to male healthy controls, whereas female individuals with GAD did not differ from female healthy controls. This megaanalysis combining worldwide data showed that differences in brain structure related to GAD are small, possibly reflecting heterogeneity or those structural alterations are not a major component of its pathophysiology

Diagnostic operationalization and phenomenological heterogeneity in psychiatry : the case of attention deficit hyperactivity disorder

Introduction. We assessed the impact of polythetic conceptualizations of mental disorders on the validity and reliability of psychiatric diagnosis, with a specific focus on two levels of heterogeneity: phenomenological and pathophysiological. Objective. We investigated this issue using attention deficit hyperactivity disorder (ADHD) as an example. Method. We examined individuals from two samples enriched for psychopathology (n = 1 255 children in Porto Alegre and 1 257 children in São Paulo, Brazil). We conducted a series of data analyses to investigate phenomenological heterogeneity, including confirmatory factor analysis. We also investigated pathophysiological heterogeneity using symptom-level regressions between ADHD symptoms and four neurocognitive processes consistently linked to ADHD (working memory, inhibitory control, intra-subject variability in reaction times, and temporal processing). Lastly, we assessed the performance of polythetic systems for reliability testing inter-rater and test-rest reliability of two well-known symptomatic scales. Results. Among the 116 200 possible combinations of symptoms to achieve DSM symptomatic threshold for categorical ADHD diagnosis, we found 173 combinations in the two independent samples, and only four were replicated in both samples (2.3%). We also found that the number of ADHD symptoms is a poor indicator of variation in the general ADHD latent trait. Overall, symptoms did not have specific profiles of associations with any of the neurocognitive processes. Reliability analyses revealed that increasing the number of items augments overall reliability of measurements. Discussion and conclusion. Our findings illustrate both potential benefits and problems inherent to the polythetic system for ADHD. Implications for the search of mechanisms underlying psychiatric disorders are discussed.Antecedentes. Evaluamos el impacto de las conceptualizaciones politécnicas de los trastornos mentales en la validez y la fiabilidad del diagnóstico psiquiátrico, con un enfoque específico en dos niveles de heterogeneidad: fenomenológico y fisiopatológico. Objetivos. Investigamos este problema utilizando el trastorno por déficit de atención e hiperactividad (TDAH) como ejemplo. Método. Examinamos individuos de dos muestras enriquecidas por psicopatología (n = 1 255 niños en Porto Alegre y 1 257 niños en São Paulo, Brasil). Llevamos a cabo una serie de análisis de datos para investigar la heterogeneidad fenomenológica, incluido el análisis factorial confirmatorio. También investigamos la heterogeneidad fisiopatológica utilizando regresiones al nivel de síntomas entre los síntomas del TDAH y cuatro procesos neurocognitivos consistentemente vinculados al TDAH (memoria de trabajo, control inhibitorio, variabilidad intrasujeto en tiempos de reacción y procesamiento temporal). Por último, evaluamos el rendimiento de los sistemas politéticos para la prueba de confiabilidad interevaluador y la confiabilidad test-rest de dos escalas sintomáticas bien conocidas. Resultados. Entre las 116 200 posibles combinaciones de síntomas para alcanzar el umbral sintomático del DSM para el diagnóstico categórico de TDAH, encontramos 173 combinaciones en las dos muestras independientes y sólo cuatro se replicaron en ambas muestras (2.3%). También encontramos que la cantidad de síntomas de TDAH no es un buen indicador de la variación en el rasgo latente general del TDAH. En general, los síntomas no tenían perfiles específicos de asociaciones con ninguno de los procesos neurocognitivos. Los análisis de confiabilidad revelaron que aumentar el número de artículos aumenta la confiabilidad general de las mediciones. Discusión y conclusión. Nuestros hallazgos ilustran tanto los beneficios potenciales como los problemas inherentes al sistema politécnico para el TDAH. Se discuten las implicaciones para la búsqueda de mecanismos subyacentes a los trastornos psiquiátricos