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1.
J Consult Clin Psychol ; 89(6): 537-550, 2021 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-34264701

RESUMO

OBJECTIVE: To determine if the Transdiagnostic Intervention for Sleep and Circadian Dysfunction (TranS-C) improves functional impairment, psychiatric symptoms, and sleep and circadian functioning. METHOD: Adults diagnosed with serious mental illness (SMI) and sleep and circadian dysfunction (N = 121) were randomly allocated to TranS-C plus usual care (TranS-C + UC; n = 61; 8 individual weekly sessions) or 6 months of Usual Care followed by Delayed Treatment with TranS-C (UC-DT; n = 60). Schizophrenia (45%) and anxiety disorders (47%) were common. Blind assessments were conducted pre-treatment, post-treatment, and 6 months later (6FU). The latter two were the post-randomization points of interest. The location was Alameda County Behavioral Health Care Services (ACBHCS), a Community Mental Health Center (CMHC) in California. RESULTS: For the primary outcomes, relative to UC-DT, TranS-C + UC was associated with reduction in functional impairment (b = -3.18, p = 0.025, d = -0.58), general psychiatric symptoms (b = -5.88, p = 0.001, d = -0.64), sleep disturbance (b = -5.55, p < .0001, d = -0.96), and sleep-related impairment (b = -9.14, p < .0001, d = -0.81) from pre-treatment to post-treatment. These effects were maintained to 6-month follow-up (6FU; d = -0.42 to -0.82), except functional impairment (d = -0.37). For the secondary outcomes, relative to UC-DT, TranS-C + UC was associated with improvement in sleep efficiency and on the Sleep Health Composite score from pre-treatment to 6FU. TranS-C + UC was also associated with reduced total wake time and wake time variability from pre-treatment to post-treatment, as well as reduced hallucinations and delusions, bedtime variability, and actigraphy measured waking activity count variability from pre-treatment to 6FU. CONCLUSIONS: A novel transdiagnostic treatment, delivered within a CMHC setting, improves selected measures of functioning, symptoms of comorbid disorders, and sleep and circadian outcomes. (PsycInfo Database Record (c) 2021 APA, all rights reserved).


Assuntos
Centros Comunitários de Saúde Mental , Transtornos Mentais/terapia , Psicoterapia/métodos , Transtornos do Sono do Ritmo Circadiano/terapia , Transtornos do Sono-Vigília/terapia , Adulto , Ansiedade/terapia , Transtornos de Ansiedade/terapia , California , Feminino , Humanos , Masculino , Transtornos Mentais/complicações , Pessoa de Meia-Idade , Esquizofrenia/terapia , Sono , Transtornos do Sono do Ritmo Circadiano/complicações , Transtornos do Sono-Vigília/complicações , Resultado do Tratamento
2.
Psychometrika ; 85(3): 815-836, 2020 09.
Artigo em Inglês | MEDLINE | ID: mdl-32856271

RESUMO

We propose a dyadic Item Response Theory (dIRT) model for measuring interactions of pairs of individuals when the responses to items represent the actions (or behaviors, perceptions, etc.) of each individual (actor) made within the context of a dyad formed with another individual (partner). Examples of its use include the assessment of collaborative problem solving or the evaluation of intra-team dynamics. The dIRT model generalizes both Item Response Theory models for measurement and the Social Relations Model for dyadic data. The responses of an actor when paired with a partner are modeled as a function of not only the actor's inclination to act and the partner's tendency to elicit that action, but also the unique relationship of the pair, represented by two directional, possibly correlated, interaction latent variables. Generalizations are discussed, such as accommodating triads or larger groups. Estimation is performed using Markov-chain Monte Carlo implemented in Stan, making it straightforward to extend the dIRT model in various ways. Specifically, we show how the basic dIRT model can be extended to accommodate latent regressions, multilevel settings with cluster-level random effects, as well as joint modeling of dyadic data and a distal outcome. A simulation study demonstrates that estimation performs well. We apply our proposed approach to speed-dating data and find new evidence of pairwise interactions between participants, describing a mutual attraction that is inadequately characterized by individual properties alone.

3.
Psychometrika ; 84(3): 802-829, 2019 09.
Artigo em Inglês | MEDLINE | ID: mdl-31297664

RESUMO

Typical Bayesian methods for models with latent variables (or random effects) involve directly sampling the latent variables along with the model parameters. In high-level software code for model definitions (using, e.g., BUGS, JAGS, Stan), the likelihood is therefore specified as conditional on the latent variables. This can lead researchers to perform model comparisons via conditional likelihoods, where the latent variables are considered model parameters. In other settings, however, typical model comparisons involve marginal likelihoods where the latent variables are integrated out. This distinction is often overlooked despite the fact that it can have a large impact on the comparisons of interest. In this paper, we clarify and illustrate these issues, focusing on the comparison of conditional and marginal Deviance Information Criteria (DICs) and Watanabe-Akaike Information Criteria (WAICs) in psychometric modeling. The conditional/marginal distinction corresponds to whether the model should be predictive for the clusters that are in the data or for new clusters (where "clusters" typically correspond to higher-level units like people or schools). Correspondingly, we show that marginal WAIC corresponds to leave-one-cluster out cross-validation, whereas conditional WAIC corresponds to leave-one-unit out. These results lead to recommendations on the general application of the criteria to models with latent variables.


Assuntos
Teorema de Bayes , Simulação por Computador/normas , Análise de Classes Latentes , Funções Verossimilhança , Análise por Conglomerados , Medidas em Epidemiologia , Humanos , Masculino , Cadeias de Markov , Método de Monte Carlo , Valor Preditivo dos Testes , Psicometria , Software
4.
Multivariate Behav Res ; 54(3): 360-381, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30919664

RESUMO

In this study we extend and assess the trifactor model for multiple-ratings data in which two different raters give independent scores for the same responses (e.g., in the GRE essay or to subset of PISA constructed-responses). The trifactor model was extended to incorporate a cross-classified data structure (e.g., items and raters) instead of a strictly hierarchical structure. we present a set of simulations to reflect the incompleteness and imbalance in real-world assessments. The effects of the rate of missingness in the data and of ignoring differences among raters are investigated using two sets of simulations. The use of the trifactor model is also illustrated with empirical data analysis using a well-known international large-scale assessment.


Assuntos
Interpretação Estatística de Dados , Modelos Psicológicos , Psicometria , Humanos
5.
Biostatistics ; 20(1): 164-179, 2019 01 01.
Artigo em Inglês | MEDLINE | ID: mdl-29309512

RESUMO

We propose the Monte Carlo local likelihood (MCLL) method for approximating maximum likelihood estimation (MLE). MCLL initially treats model parameters as random variables, sampling them from the posterior distribution as in a Bayesian model. The likelihood function is then approximated up to a constant by fitting a density to the posterior samples and dividing the approximate posterior density by the prior. In the MCLL algorithm, the posterior density is estimated using local likelihood density estimation, in which the log-density is locally approximated by a polynomial function. We also develop a new method that allows users to efficiently compute standard errors and the Bayes factor. Two empirical and three simulation studies are provided to demonstrate the performance of the MCLL method.


Assuntos
Bioestatística/métodos , Interpretação Estatística de Dados , Funções Verossimilhança , Método de Monte Carlo , Poluição do Ar/estatística & dados numéricos , Animais , Teorema de Bayes , Simulação por Computador , Humanos , Transtornos Respiratórios/epidemiologia , Comportamento Sexual Animal/fisiologia , Urodelos/fisiologia
6.
J Am Acad Child Adolesc Psychiatry ; 57(10): 742-754, 2018 10.
Artigo em Inglês | MEDLINE | ID: mdl-30274649

RESUMO

OBJECTIVE: To determine whether an intervention to reduce eveningness chronotype improves sleep, circadian, and health (emotional, cognitive, behavioral, social, physical) outcomes. METHOD: Youth aged 10 to 18 years with an evening chronotype and who were "at risk" in 1 of 5 health domains were randomized to: (a) Transdiagnostic Sleep and Circadian Intervention for Youth (TranS-C; n = 89) or (b) Psychoeducation (PE; n = 87) at a university-based clinic. Treatments were 6 individual, weekly 50-minute sessions during the school year. TranS-C addresses sleep and circadian problems experienced by youth by integrating evidence-based treatments derived from basic research. PE provides education on the interrelationship between sleep, stress, diet, and health. RESULTS: Relative to PE, TranS-C was not associated with greater pre-post change for total sleep time (TST) or bed time (BT) on weeknights but was associated with greater reduction in evening circadian preference (pre-post increase of 3.89 points, 95% CI = 2.94-4.85, for TranS-C, and 2.01 points, 95% CI = 1.05-2.97 for PE, p = 0.006), earlier endogenous circadian phase, less weeknight-weekend discrepancy in TST and wakeup time, less daytime sleepiness, and better self-reported sleep via youth and parent report. In terms of functioning in the five health domains, relative to PE, TranS-C was not associated with greater pre-post change on the primary outcome. However, there were significant interactions favoring TranS-C on the Parent-Reported Composite Risk Scores for cognitive health. CONCLUSION: For at-risk youth, the evidence supports the use of TranS-C over PE for improving sleep and circadian functioning, and improving health on selected outcomes. CLINICAL TRIAL REGISTRATION INFORMATION: Triple Vulnerability? Circadian Tendency, Sleep Deprivation and Adolescence. https://clinicaltrials.gov; NCT01828320.


Assuntos
Ritmo Circadiano/fisiologia , Privação do Sono/prevenção & controle , Sono/fisiologia , Adolescente , Criança , Feminino , Nível de Saúde , Humanos , Masculino , Autorrelato , Fatores de Tempo
7.
Psychometrika ; 83(4): 785-808, 2018 12.
Artigo em Inglês | MEDLINE | ID: mdl-30120699

RESUMO

We propose a class of confirmatory factor analysis models that include multiple sets of secondary or specific factors and a general factor. The general factor accounts for the common variance among manifest variables, whereas multiple sets of secondary factors account for the remaining source-specific dependency among subsets of manifest variables. A special case of the model is further proposed which constrains the specific factor loadings to be proportional to the general factor loadings. This proportional model substantially reduces the number of model parameters while preserving the essential structure of the general model. Furthermore, the proportional model allows for the interpretation of latent variables as the expected values of the observed manifest variables, decomposition of the variances, and the inclusion of interactions, similar to generalizability theory. We provide two applications to illustrate the utility of the proposed class of models.


Assuntos
Análise Fatorial , Análise Multivariada , Sucesso Acadêmico , Criança , Interpretação Estatística de Dados , Humanos , Psicometria/métodos
8.
Stat Med ; 37(3): 343-356, 2018 02 10.
Artigo em Inglês | MEDLINE | ID: mdl-29082538

RESUMO

Maximum likelihood estimation of models for binary longitudinal data is typically inconsistent if the dependence structure is misspecified. Unfortunately, diagnostics specifically designed for detecting such misspecifications are scant. We develop residuals and diagnostic tests based on comparing observed and expected frequencies of response patterns over time in the presence of arbitrary time-varying and time-invariant covariates. To overcome the sparseness problem, we use lower-order marginal tables, such as two-way tables for pairs of time-points, aggregated over covariate patterns. Our proposed pairwise concordance residuals are valuable for exploratory diagnostics and for constructing both generic tests for misspecified dependence structure as well as targeted adjacent pair concordance tests for excess serial dependence. The proposed methods are straightforward to implement and work well for general situations, regardless of the number of time-points and the number and types of covariates.


Assuntos
Biometria/métodos , Testes Diagnósticos de Rotina , Funções Verossimilhança , Simulação por Computador , Interpretação Estatística de Dados , Humanos , Estudos Longitudinais , Modelos Estatísticos , Sensibilidade e Especificidade
9.
Trials ; 18(1): 539, 2017 Nov 14.
Artigo em Inglês | MEDLINE | ID: mdl-29137655

RESUMO

BACKGROUND: The Memory Support Intervention was developed in response to evidence showing that: (1) patient memory for treatment is poor, (2) poor memory for treatment is associated with poorer adherence and poorer outcome, (3) the impact of memory impairment can be minimized by the use of memory support strategies and (4) improved memory for treatment improves outcome. The aim of this study protocol is to conduct a confirmatory efficacy trial to test whether the Memory Support Intervention improves illness course and functional outcomes. As a "platform" for the next step in investigating this approach, we focus on major depressive disorder (MDD) and cognitive therapy (CT). METHOD/DESIGN: Adults with MDD (n = 178, including 20% for potential attrition) will be randomly allocated to CT + Memory Support or CT-as-usual and will be assessed at baseline, post treatment and at 6 and 12 months' follow-up (6FU and 12FU). We will compare the effects of CT + Memory Support vs. CT-as-usual to determine if the new intervention improves the course of illness and reduces functional impairment (aim 1). We will determine if patient memory for treatment mediates the relationship between treatment condition and outcome (aim 2). We will evaluate if previously reported poor treatment response subgroups moderate target engagement (aim 3). DISCUSSION: The Memory Support Intervention has been developed to be "transdiagnostic" (relevant to a broad range of mental disorders) and "pantreatment" (relevant to a broad range of types of treatment). This study protocol describes a "next step" in the treatment development process by testing the Memory Support Intervention for major depressive disorder (MDD) and cognitive therapy (CT). If the results are promising, future directions will test the applicability to other kinds of interventions and disorders and in other settings. TRIAL REGISTRATION: ClinicalTrials.gov, ID: NCT01790919 . Registered on 6 October 2016.


Assuntos
Afeto , Cognição , Terapia Cognitivo-Comportamental , Transtorno Depressivo Maior/terapia , Memória , California , Protocolos Clínicos , Transtorno Depressivo Maior/diagnóstico , Transtorno Depressivo Maior/psicologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Prospectivos , Projetos de Pesquisa , Fatores de Tempo , Resultado do Tratamento
10.
Psychometrika ; 2017 Feb 28.
Artigo em Inglês | MEDLINE | ID: mdl-28247165

RESUMO

We present a variational maximization-maximization algorithm for approximate maximum likelihood estimation of generalized linear mixed models with crossed random effects (e.g., item response models with random items, random raters, or random occasion-specific effects). The method is based on a factorized variational approximation of the latent variable distribution given observed variables, which creates a lower bound of the log marginal likelihood. The lower bound is maximized with respect to the factorized distributions as well as model parameters. With the proposed algorithm, a high-dimensional intractable integration is translated into a two-dimensional integration problem. We incorporate an adaptive Gauss-Hermite quadrature method in conjunction with the variational method in order to increase computational efficiency. Numerical studies show that under the small sample size conditions that are considered the proposed algorithm outperforms the Laplace approximation.

11.
Stat Methods Med Res ; 26(4): 1756-1773, 2017 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-26116615

RESUMO

Generalized linear mixed models for longitudinal data assume that responses at different occasions are conditionally independent, given the random effects and covariates. Although this assumption is pivotal for consistent estimation, violation due to serial dependence is hard to assess by model elaboration. We therefore propose a targeted diagnostic test for serial dependence, called the transition model test (TMT), that is straightforward and computationally efficient to implement in standard software. The TMT is shown to have larger power than general misspecification tests. We also propose the targeted root mean squared error of approximation (TRSMEA) as a measure of the population misfit due to serial dependence.


Assuntos
Modelos Lineares , Estudos Longitudinais , Humanos , Funções Verossimilhança , Ensaios Clínicos Controlados Aleatórios como Assunto/métodos , Transtornos Respiratórios/tratamento farmacológico , Software
12.
Trials ; 17(1): 606, 2016 12 20.
Artigo em Inglês | MEDLINE | ID: mdl-27998295

RESUMO

BACKGROUND: Severe mental illness (SMI) is common, chronic and difficult to treat. Sleep and circadian dysfunctions are prominent correlates of SMI, yet have been minimally studied in ways that reflect the complexity of the sleep problems experienced. Prior treatment studies have been disorder-focused-they have treated a specific sleep problem in a specific diagnostic group. However, real life sleep and circadianproblems are not so neatly categorized, particularly in SMI where features of insomnia overlap with hypersomnia, delayed sleep phase and irregular sleep-wake schedules. Accordingly, the aim of this studyprotocol is to test the hypothesis that a Transdiagnostic Intervention for Sleep and Circadian Dysfunction (TranS-C) will improve functional impairment, disorder-focused symptoms and sleep and circadian functioning. Participants across DSM diagnoses and across common sleep and circadian problems are eligible. The elements of TranS-C are efficacious across SMI in research settings with research-based providers. The next step is to test TranS-C in a community setting. Accordingly, this study is being conducted within Alameda County Behavioral Health Care Services (ACBHCS), the Community Mental Health Centre (CMHC) for Alameda County. METHODS/DESIGN: 120 adults diagnosed with SMI and sleep and circadian dysfunction within ACBHCS will be randomly allocated to TranS-C (n = 60) or 6-months of Usual Care followed by Delayed Treatment with TranS-C (UC-DT; n = 60). TranS-C is modularized and delivered across eight to twelve 50-minute, weekly, individual sessions. All participants will be assessed before and immediately following treatment and again 6 months later. Primary analysis will examine whether TranS-C significantly improves functional impairment, disorder-specific symptoms and sleep and circadian functioning, relative to UC-DT. Exploratory analysis will examine whether improvements in sleep and circadian functioning predict reduction in functional impairment and disorder-specific symptoms, and whether the intervention effects are mediated by improved sleep and circadian functioning and moderated by previously reported risk factors (demographics, symptom severity, medications, psychiatric and medical comorbidity). DISCUSSION: This trial tests an important and understudied mechanism-dysregulated sleep and circadian rhythms-in SMI, a novel transdiagnostic treatment approach, in a community setting so as to contribute to the goal of bridging the gap between research and practice. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT02469233 . Registered on 9 June 2015.


Assuntos
Ritmo Circadiano , Transtornos Mentais/terapia , Psicoterapia/métodos , Transtornos do Sono do Ritmo Circadiano/terapia , Sono , Adulto , California , Protocolos Clínicos , Feminino , Humanos , Masculino , Transtornos Mentais/diagnóstico , Transtornos Mentais/fisiopatologia , Transtornos Mentais/psicologia , Pessoa de Meia-Idade , Estudos Prospectivos , Projetos de Pesquisa , Índice de Gravidade de Doença , Transtornos do Sono do Ritmo Circadiano/diagnóstico , Transtornos do Sono do Ritmo Circadiano/fisiopatologia , Transtornos do Sono do Ritmo Circadiano/psicologia , Inquéritos e Questionários , Fatores de Tempo , Resultado do Tratamento , Adulto Jovem
13.
Behav Res Ther ; 81: 35-46, 2016 06.
Artigo em Inglês | MEDLINE | ID: mdl-27089159

RESUMO

Patients exhibit poor memory for treatment. A novel Memory Support Intervention, derived from basic science in cognitive psychology and education, is tested with the goal of improving patient memory for treatment and treatment outcome. Adults with major depressive disorder (MDD) were randomized to 14 sessions of cognitive therapy (CT)+Memory Support (n = 25) or CT-as-usual (n = 23). Outcomes were assessed at baseline, post-treatment and 6 months later. Memory support was greater in CT+Memory Support compared to the CT-as-usual. Compared to CT-as-usual, small to medium effect sizes were observed for recall of treatment points at post-treatment. There was no difference between the treatment arms on depression severity (primary outcome). However, the odds of meeting criteria for 'response' and 'remission' were higher in CT+Memory Support compared with CT-as-usual. CT+Memory Support also showed an advantage on functional impairment. While some decline was observed, the advantage of CT+Memory Support was evident through 6-month follow-up. Patients with less than 16 years of education experience greater benefits from memory support than those with 16 or more years of education. Memory support can be manipulated, may improve patient memory for treatment and may be associated with an improved outcome.


Assuntos
Terapia Cognitivo-Comportamental , Transtorno Depressivo Maior/terapia , Aprendizagem , Adulto , Feminino , Humanos , Masculino , Resultado do Tratamento , Adulto Jovem
14.
Psychometrika ; 81(3): 830-50, 2016 09.
Artigo em Inglês | MEDLINE | ID: mdl-26645083

RESUMO

A first-order autoregressive growth model is proposed for longitudinal binary item analysis where responses to the same items are conditionally dependent across time given the latent traits. Specifically, the item response probability for a given item at a given time depends on the latent trait as well as the response to the same item at the previous time, or the lagged response. An initial conditions problem arises because there is no lagged response at the initial time period. We handle this problem by adapting solutions proposed for dynamic models in panel data econometrics. Asymptotic and finite sample power for the autoregressive parameters are investigated. The consequences of ignoring local dependence and the initial conditions problem are also examined for data simulated from a first-order autoregressive growth model. The proposed methods are applied to longitudinal data on Korean students' self-esteem.


Assuntos
Modelos Estatísticos , Autoimagem , Estatística como Assunto , Estudantes/psicologia , Humanos , Funções Verossimilhança , Estudos Longitudinais , Modelos Teóricos , Análise de Regressão , República da Coreia
15.
J Consult Clin Psychol ; 83(3): 564-77, 2015 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-25622197

RESUMO

OBJECTIVE: To determine if a treatment for interepisode bipolar disorder I patients with insomnia improves mood state, sleep, and functioning. METHOD: Alongside psychiatric care, interepisode bipolar disorder I participants with insomnia were randomly allocated to a bipolar disorder-specific modification of cognitive behavior therapy for insomnia (CBTI-BP; n = 30) or psychoeducation (PE; n = 28) as a comparison condition. Outcomes were assessed at baseline, the end of 8 sessions of treatment, and 6 months later. This pilot was conducted to determine initial feasibility and generate effect size estimates. RESULTS: During the 6-month follow-up, the CBTI-BP group had fewer days in a bipolar episode relative to the PE group (3.3 days vs. 25.5 days). The CBTI-BP group also experienced a significantly lower hypomania/mania relapse rate (4.6% vs. 31.6%) and a marginally lower overall mood episode relapse rate (13.6% vs. 42.1%) compared with the PE group. Relative to PE, CBTI-BP reduced insomnia severity and led to higher rates of insomnia remission at posttreatment and marginally higher rates at 6 months. Both CBTI-BP and PE showed statistically significant improvement on selected sleep and functional impairment measures. The effects of treatment were well sustained through follow-up for most outcomes, although some decline on secondary sleep benefits was observed. CONCLUSIONS: CBTI-BP was associated with reduced risk of mood episode relapse and improved sleep and functioning on certain outcomes in bipolar disorder. Hence, sleep disturbance appears to be an important pathway contributing to bipolar disorder. The need to develop bipolar disorder-specific sleep diary scoring standards is highlighted.


Assuntos
Afeto/fisiologia , Transtorno Bipolar/psicologia , Terapia Cognitivo-Comportamental/métodos , Distúrbios do Início e da Manutenção do Sono/terapia , Sono/fisiologia , Adulto , Transtorno Bipolar/complicações , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Projetos Piloto , Distúrbios do Início e da Manutenção do Sono/complicações , Distúrbios do Início e da Manutenção do Sono/psicologia , Resultado do Tratamento
16.
Psychometrika ; 79(1): 84-104, 2014 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-24337937

RESUMO

An additive multilevel item structure (AMIS) model with random residuals is proposed. The model includes multilevel latent regressions of item discrimination and item difficulty parameters on covariates at both item and item category levels with random residuals at both levels. The AMIS model is useful for explanation purposes and also for prediction purposes as in an item generation context. The parameters can be estimated with an alternating imputation posterior algorithm that makes use of adaptive quadrature, and the performance of this algorithm is evaluated in a simulation study.


Assuntos
Modelos Teóricos , Psicometria/métodos , Estatística como Assunto/métodos , Humanos
17.
Psychometrika ; 78(4): 685-709, 2013 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-24092484

RESUMO

Group-level variance estimates of zero often arise when fitting multilevel or hierarchical linear models, especially when the number of groups is small. For situations where zero variances are implausible a priori, we propose a maximum penalized likelihood approach to avoid such boundary estimates. This approach is equivalent to estimating variance parameters by their posterior mode, given a weakly informative prior distribution. By choosing the penalty from the log-gamma family with shape parameter greater than 1, we ensure that the estimated variance will be positive. We suggest a default log-gamma(2,λ) penalty with λ → 0, which ensures that the maximum penalized likelihood estimate is approximately one standard error from zero when the maximum likelihood estimate is zero, thus remaining consistent with the data while being nondegenerate. We also show that the maximum penalized likelihood estimator with this default penalty is a good approximation to the posterior median obtained under a noninformative prior.Our default method provides better estimates of model parameters and standard errors than the maximum likelihood or the restricted maximum likelihood estimators. The log-gamma family can also be used to convey substantive prior information. In either case-pure penalization or prior information-our recommended procedure gives nondegenerate estimates and in the limit coincides with maximum likelihood as the number of groups increases.


Assuntos
Psicometria/métodos , Estatística como Assunto/métodos , Humanos , Funções Verossimilhança , Modelos Estatísticos
18.
Stat Med ; 32(23): 4071-89, 2013 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-23670939

RESUMO

Fixed-effects meta-analysis has been criticized because the assumption of homogeneity is often unrealistic and can result in underestimation of parameter uncertainty. Random-effects meta-analysis and meta-regression are therefore typically used to accommodate explained and unexplained between-study variability. However, it is not unusual to obtain a boundary estimate of zero for the (residual) between-study standard deviation, resulting in fixed-effects estimates of the other parameters and their standard errors. To avoid such boundary estimates, we suggest using Bayes modal (BM) estimation with a gamma prior on the between-study standard deviation. When no prior information is available regarding the magnitude of the between-study standard deviation, a weakly informative default prior can be used (with shape parameter 2 and rate parameter close to 0) that produces positive estimates but does not overrule the data, leading to only a small decrease in the log likelihood from its maximum. We review the most commonly used estimation methods for meta-analysis and meta-regression including classical and Bayesian methods and apply these methods, as well as our BM estimator, to real datasets. We then perform simulations to compare BM estimation with the other methods and find that BM estimation performs well by (i) avoiding boundary estimates; (ii) having smaller root mean squared error for the between-study standard deviation; and (iii) better coverage for the overall effects than the other methods when the true model has at least a small or moderate amount of unexplained heterogeneity.


Assuntos
Teorema de Bayes , Funções Verossimilhança , Metanálise como Assunto , Análise de Regressão , Simulação por Computador , Depressão/terapia , Dipiridamol/farmacologia , Exercício Físico/psicologia , Humanos , Inibidores da Agregação Plaquetária/farmacologia , Acidente Vascular Cerebral/prevenção & controle
19.
J Neurovirol ; 19(2): 123-30, 2013 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-23430713

RESUMO

Specific neuronal spatial distributional patterns have previously been correlated with increasing severity of HIV-associated dementia (HAD). As astrocytes are also a putative site of neurotoxicity, we investigated the spatial relationships of astrocytes with pyramidal and interneurons in the superior frontal gyrus from 29 patients who died from acquired immunodeficiency syndrome. Frontal cortical brain tissue was taken from diseased HIV patients who had been assessed for the presence and severity of HAD using the Memorial Sloan-Kettering Scale. No correlation was found between neuronal density and severity of dementia. However, the pattern of astrocytes became more clustered as dementia progressed. Bivariate spatial pattern analysis of neuronal populations with astrocytes revealed that, with increasing dementia severity, astrocytes and large pyramidal neurons increasingly "repelled" each other, while astrocytes and interneurons evidenced increasing "attraction." This implies that astrocytes may be more likely to be situated in the vicinity of surviving interneurons but less likely to be situated near surviving large pyramidal neurons in the setting of progressing HAD.


Assuntos
Complexo AIDS Demência/patologia , Astrócitos/patologia , Interneurônios/patologia , Células Piramidais/patologia , Complexo AIDS Demência/fisiopatologia , Comunicação Celular , Contagem de Células , Humanos , Masculino , Tamanho do Órgão , Células Piramidais/fisiopatologia , Índice de Gravidade de Doença
20.
Psychosom Med ; 72(7): 656-63, 2010 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-20668284

RESUMO

OBJECTIVE: To conduct a randomized, controlled, two-stage trial in the treatment of bulimia nervosa, comparing cognitive-behavioral therapy (CBT) versus motivational enhancement in Phase 1 followed by group versus individual CBT in Phase 2. METHODS: A total of 225 patients with bulimia nervosa or eating disorder not otherwise specified (EDNOS) were recruited into a randomized controlled trial lasting 12 weeks with follow-ups at 1 year and 2.5 years. RESULTS: Patients improved significantly across all of the interventions with no differences in outcome or treatment adherence. Including motivational enhancement therapy rather than a CBT first phase of treatment did not affect outcome. CONCLUSIONS: Outcome differences between individual and group CBT were minor, suggesting that group treatment prefaced by a short individual intervention may be a cost-effective alternative to purely individual treatment.


Assuntos
Terapia Comportamental/métodos , Bulimia Nervosa/terapia , Terapia Cognitivo-Comportamental/métodos , Motivação , Adulto , Bulimia Nervosa/psicologia , Transtornos da Alimentação e da Ingestão de Alimentos/terapia , Feminino , Seguimentos , Humanos , Relações Interpessoais , Masculino , Cooperação do Paciente , Pacientes Desistentes do Tratamento , Psicoterapia de Grupo/métodos , Projetos de Pesquisa , Resultado do Tratamento
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