Switching Principal Component Analysis for Modeling Means and Covariance Changes Over Time

Many psychological theories predict that cognitions, affect, action tendencies, and other variables change across time in mean level as well as in covariance structure. Often such changes are rather abrupt, because they are caused by sudden events. To capture such changes, one may repeatedly measure the variables under study for a single individual and examine whether the resulting multivariate time series contains a number of phases with different means and covariance structures. The latter task is challenging, however. First, in many cases, it is unknown how many phases there are and when new phases start. Second, often a rather large number of variables is involved, complicating the interpretation of the covariance pattern within each phase. To take up this challenge, we present switching principal component analysis (PCA). Switching PCA detects phases of consecutive observations or time points (in single subject data) with similar means and/or covariation structures, and performs a PCA per phase to yield insight into its covariance structure. An algorithm for fitting switching PCA solutions as well as a model selection procedure are presented and evaluated in a simulation study. Finally, we analyze empirical data on cardiorespiratory recordings

Cognitive-behaviour therapy for patients with Abridged Somatization Disorder (SSI 4,6) in primary care: a randomized, controlled study

Abstract Background Somatoform disorders are characterized by the presence of multiple somatic symptoms without an organic cause that completely explains their symptoms. These patients generate a high cost in health services. We aim to evaluate the effectiveness and feasibility of a cognitive-behaviour therapy (CBT) programme, administered in group and individual formats in primary care for patients who are diagnosed with abridged somatization disorder. Method/design Design: Multicentre, randomized, controlled trial involving 3 groups, one of which is the control group consisting of standardized recommended treatment for somatization disorder in primary care (Smith's norms) and the 2 others, the intervention groups, consisting of cognitive-behavioural therapy (10 sessions) administered in individual format (intervention group 1) or in group format (intervention group 2). Setting: 29 primary care health centres in the province of Zaragoza and 3 primary care health centres in the province of Mallorca, Spain. Sample: N = 204 patients, (68 in each of the three groups), aged 18–65 years, able to understand and read Spanish, who fulfil Escobar's criteria of Abridgged Somatization Disorder (SSI 4,6), stable with pharmacotherapy over the previous month, and who will remain stable for the next 3 months in the doctor's opinion, having signed informed consent. Intervention: Control group: Standardized recommended treatment for somatization disorder in primary care (Smith's norms). Intervention group: 10 weekly sessions of CBT, following a protocol designed by Prof. Escobar's group at UMDNJ, USA. There are 2 different treatment conditions: individual and group format. Measurements: Survey on the use of health services, number and severity of somatic symptoms, anxiety, depression, quality of life and clinical global impression. The interviewers will not know which group the patient belongs to (blind). The assessments will be carried out at baseline, post-treatment, 6 months and 12 post-treatment. Main variables: Utilization of health services, number and severity of somatic symptoms. Analysis: The analysis will be per intent to treat. We will use the general linear models of the SPSS v.15 statistical package, to analyse the effect of treatment on the result variable (utilization of health services, number and severity of somatic symptoms). Discussion It is necessary to develop more effective psychological treatments for somatoform disorders. This randomised clinical trial will determine whether cognitive behaviour therapy, both in group or in individual format, is effective for the treatment of these patients. Trial registration Current controlled trials ISRCTN69944771</p

Development and evaluation of an instrument for the critical appraisal of randomized controlled trials of natural products

<p>Abstract</p> <p>Background</p> <p>The efficacy of natural products (NPs) is being evaluated using randomized controlled trials (RCTs) with increasing frequency, yet a search of the literature did not identify a widely accepted critical appraisal instrument developed specifically for use with NPs. The purpose of this project was to develop and evaluate a critical appraisal instrument that is sufficiently rigorous to be used in evaluating RCTs of conventional medicines, and also has a section specific for use with single entity NPs, including herbs and natural sourced chemicals.</p> <p>Methods</p> <p>Three phases of the project included: 1) using experts and a Delphi process to reach consensus on a list of items essential in describing the identity of an NP; 2) compiling a list of non-NP items important for evaluating the quality of an RCT using systematic review methodology to identify published instruments and then compiling item categories that were part of a validated instrument and/or had empirical evidence to support their inclusion and 3) conducting a field test to compare the new instrument to a published instrument for usefulness in evaluating the quality of 3 RCTs of a NP and in applying results to practice.</p> <p>Results</p> <p>Two Delphi rounds resulted in a list of 15 items essential in describing NPs. Seventeen item categories fitting inclusion criteria were identified from published instruments for conventional medicines. The new assessment instrument was assembled based on content of the two lists and the addition of a Reviewer's Conclusion section. The field test of the new instrument showed good criterion validity. Participants found it useful in translating evidence from RCTs to practice.</p> <p>Conclusion</p> <p>A new instrument for the critical appraisal of RCTs of NPs was developed and tested. The instrument is distinct from other available assessment instruments for RCTs of NPs in its systematic development and validation. The instrument is ready to be used by pharmacy students, health care practitioners and academics and will continue to be refined as required.</p

The role of teacher behavior management in the development of disruptive behaviors: an intervention study with the good behavior game

Abstract The role of teacher behavior management for children’s disruptive behavior development (hyperactive and oppositional behavior) was investigated using a universal classroom preventive intervention study. Five-hundred seventy children were followed from second to third grade of elementary school. Observations of teacher behavior management and children’s on-task and off-task classroom behavior and peer reports of hyperactive and oppositional behavior were available. Results showed that the reduced use of negative remarks of intervention teachers predicted children’s increase in on-task behavior and decrease in talking-out behavior. These improved children’s classroom behaviors in turn mediated the impact of the intervention on the development of hyperactive and oppositional behavior over the studied period. These results were similar for girls and boys. The results underscore the role of teachers’ classroom management strategies in improving children’s classroom behavior, which, in turn is an important component in the reduction of disruptive behavior development

N-of-1 trials in child and adolescent psychiatry: A closer look at stimulants

© 2018 Uitgeverij Boom. All rights reserved. Background : An N-of-1 trial is a clinical trial studying the response of an individual to a particular intervention or different interventions in an objective, systematic way. Aim: To evaluate both the applications and the methodology of N-of-1 trials in child and adolescent psychiatry. Method: A systematic review using PubMed and Embase assessing N-of-1 trials published during the period 1986 -July 2016 with the following key-word:'N-of-1'. results 20 articles were induded. AII articles used N-of-1 trials to evaluate the effect of stimulant medications in children and adolescents with adhd. Most articles recommended the use of the N-of-1 methodology in clinical practice, despite the large variation in methodology and in outcome interpretation of N-of-1 trials.The 20 articles didn't meet the current quality standards for N-of-1 trials. Conclusion: Despite the advantages of N-of-1 trials, the applications in child and adolescent psychiatry turn out to be rather limited and specific. N-of-1 trials have more to offer regarding both clinical practice and research in child and adolescent psychiatry. If the methodological recommendations are sufficiently met, N-of-1 trials could provide a useful and applicable tool for the child-And adolescent psychiatrist to offer individual patient care.status: publishe

Switching PCA for modeling changes in the underlying structure of multivariate time series data

Behavioral researchers are often interested in the underlying structure of multivariate time series data. For instance, given multiple measurements of a set of variables for one subject, one may wonder whether some of the variables covary across time or whether they all fluctuate independently of one another, and whether the underlying structure is the same across all measurements or varies over time. For example, when something happens between two measurements, the amount or nature of covariation in the data can change. To explore such structural differences across time, Switching PCA is developed. Using Switching PCA, clusters of sequential (i.e., a time contiguity constraint is imposed on the clustering, implying that each cluster consists of consecutive measurements only) measurements are induced, according to the underlying structure, and the data within each cluster are modeled by a separate PCA. An algorithm for fitting Switching PCA models is presented. The value of the model for empirical research is demonstrated.status: publishe

A clusterwise simultaneous component method for capturing within-cluster differences in component variances and correlations

<p>This paper presents a clusterwise simultaneous component analysis for tracing structural differences and similarities between data of different groups of subjects. This model partitions the groups into a number of clusters according to the covariance structure of the data of each group and performs a simultaneous component analysis with invariant pattern restrictions (SCA-P) for each cluster. These restrictions imply that the model allows for between-group differences in the variances and the correlations of the cluster-specific components. As such, clusterwise SCA-P is more flexible than the earlier proposed clusterwise SCA-ECP model, which imposed equal average cross-products constraints on the component scores of the groups that belong to the same cluster. Using clusterwise SCA-P, a finer-grained, yet parsimonious picture of the group differences and similarities can be obtained. An algorithm for fitting clusterwise SCA-P solutions is presented and its performance is evaluated by means of a simulation study. The value of the model for empirical research is illustrated with data from psychiatric diagnosis research.</p>