A treeless absolutely random forest with closed-form estimators of expected proximities.

We introduce a simple variant of a Purely Random Forest, an Absolute Random Forest (ARF) for clustering. At every node splits of units are determined by a randomly chosen feature and a random threshold drawn from a uniform distribution whose support, the range of the selected feature in the root node, does not change. This enables closed-form estimators of parameters, such as pairwise proximities, to be obtained without having to grow a forest. The probabilistic structure corresponding to an ARF is called a Treeless Absolute Random Forest (TARF). With high probability, the algorithm will split units whose feature vectors are far apart and keep together units whose feature vectors are similar. Thus, the underlying structure of the data drives the growth of the tree. The expected value of pairwise proximities is obtained for three pathway functions. One, a completely common pathway function, is an indicator of whether a pair of units follow the same path from the root to the leaf node. The properties of TARF-based proximity estimators for clustering and classification are compared to other methods in eight real-world data sets and in simulations. Results show substantial performance and computing efficiencies of particular value for large data sets.

Neurobiology and Treatment of Posttraumatic Stress Disorder.

The recent worldwide surge of warfare and hostilities exposes increasingly large numbers of individuals to traumatic events, placing them at risk of developing posttraumatic stress disorder (PTSD) and challenging both clinicians and service delivery systems. This overview summarizes and updates the core knowledge of the genetic, molecular, and neural circuit features of the neurobiology of PTSD and advances in evidence-based psychotherapy, pharmacotherapy, neuromodulation, and digital treatments. While the complexity of the neurobiology and the biological and clinical heterogeneity of PTSD have challenged clinicians and researchers, there is an emerging consensus concerning the underlying mechanisms and approaches to diagnosis, treatment, and prevention of PTSD. This update addresses PTSD diagnosis, prevalence, course, risk factors, neurobiological mechanisms, current standard of care, and innovations in next-generation treatment and prevention strategies. It provides a comprehensive summary and concludes with areas of research for integrating advances in the neurobiology of the disorder with novel treatment and prevention targets.

Pilot Study of Prism EFP NeuroFeedback in Adult ADHD.

OBJECTIVE: A pilot study to preliminarily examine the effects of Prism EFP NeuroFeedback (NF) in adult ADHD. METHOD: Prism EFP NF is a form of NF specifically designed to target emotional dysregulation (ED) through down regulation of amygdala activity. Prism EFP NF has been shown to improve other disorders with significant ED. Nine participants with adult ADHD received an open trial of Prism EFP NF consisting of fifteen sessions over 8 weeks; all completed at least 5 weeks of treatment with seven completing all 8 weeks. Outcomes were assessed by change in ADHD symptoms from baseline to End of Treatment. RESULTS: About two-third reduction was seen in total DSM ADHD symptom scores (primary outcome measure) with improvement observed in all other clinical measures. No significant adverse events were seen. CONCLUSION: This preliminary trial found substantial effects of Prism EFP NF on ADHD/ED symptoms and global impairment.

Amygdala-derived-EEG-fMRI-pattern neurofeedback for the treatment of chronic post-traumatic stress disorder. A prospective, multicenter, multinational study evaluating clinical efficacy.

We conducted a prospective, single arm, multisite, multinational, open label trial assessing the safety and efficacy of a novel amygdala derived neurofeedback treatment, designated Amygdala-Derived-EFP, for chronic PTSD. Participants, including veterans and civilians, underwent screening, training, 15 neurofeedback sessions over 8 weeks and; baseline, termination (8 weeks) and 3 month post treatment assessments with validated measures. The primary endpoint was more than 50 % of the participants demonstrating a Minimally Clinically Important Difference (MCID) defined as a 6-point reduction, on the Clinician Administered PTSD Scale (CAPS-5) total score at 3 months. Secondary measures included the PCL-5, ERQ, PHQ-9, and CGI. Statistical analyses were performed using SAS®V9.4. The primary endpoint was met, with a CAPS-5 MCID response rate of 66.7 %. The average reduction in CAPS-5 total scores at 3 month follow up was 13.5 points, more than twice the MCID. Changes from baseline in CAPS-5, PCL-5, PHQ-9 scores at 8 weeks and the 3 month follow-up demonstrated statistically significant improvements in response and; demonstrated effect sizes ranging from 0.46 to 1.07. Adverse events were mild and resolved after treatment. This study builds on prior research demonstrating similar outcomes using amygdala-derived neurofeedback. Positive attributes of this therapy include monitoring by non-physician personnel, affordability, accessibility, and tolerability.

Circulating cell-free mitochondrial DNA levels and glucocorticoid sensitivity in a cohort of male veterans with and without combat-related PTSD.

Circulating cell-free mitochondrial DNA (ccf-mtDNA) is a biomarker of cellular injury or cellular stress and is a potential novel biomarker of psychological stress and of various brain, somatic, and psychiatric disorders. No studies have yet analyzed ccf-mtDNA levels in post-traumatic stress disorder (PTSD), despite evidence of mitochondrial dysfunction in this condition. In the current study, we compared plasma ccf-mtDNA levels in combat trauma-exposed male veterans with PTSD (n = 111) with those who did not develop PTSD (n = 121) and also investigated the relationship between ccf mt-DNA levels and glucocorticoid sensitivity. In unadjusted analyses, ccf-mtDNA levels did not differ significantly between the PTSD and non-PTSD groups (t = 1.312, p = 0.191, Cohen's d = 0.172). In a sensitivity analysis excluding participants with diabetes and those using antidepressant medication and controlling for age, the PTSD group had lower ccf-mtDNA levels than did the non-PTSD group (F(1, 179) = 5.971, p = 0.016, partial η2 = 0.033). Across the entire sample, ccf-mtDNA levels were negatively correlated with post-dexamethasone adrenocorticotropic hormone (ACTH) decline (r = -0.171, p = 0.020) and cortisol decline (r = -0.149, p = 0.034) (viz., greater ACTH and cortisol suppression was associated with lower ccf-mtDNA levels) both with and without controlling for age, antidepressant status and diabetes status. Ccf-mtDNA levels were also significantly positively associated with IC50-DEX (the concentration of dexamethasone at which 50% of lysozyme activity is inhibited), a measure of lymphocyte glucocorticoid sensitivity, after controlling for age, antidepressant status, and diabetes status (ß = 0.142, p = 0.038), suggesting that increased lymphocyte glucocorticoid sensitivity is associated with lower ccf-mtDNA levels. Although no overall group differences were found in unadjusted analyses, excluding subjects with diabetes and those taking antidepressants, which may affect ccf-mtDNA levels, as well as controlling for age, revealed decreased ccf-mtDNA levels in PTSD. In both adjusted and unadjusted analyses, low ccf-mtDNA levels were associated with relatively increased glucocorticoid sensitivity, often reported in PTSD, suggesting a link between mitochondrial and glucocorticoid-related abnormalities in PTSD.

Predictors of PTSD symptoms in brazilian police officers: the synergy of negative affect and peritraumatic dissociation / Preditores de sintomas de transtorno de estresse pós-traumático em policiais brasileiros: a interação entre afeto negativo e dissociação peritraumática

BACKGROUND: Exposure to traumatic events is a necessary but not a sufficient condition for the development of posttraumatic stress disorder (PTSD). Pretrauma, peritrauma and posttrauma factors interact to impact on symptom severity. The aim of the present study is to determine risk factors for PTSD symptoms in Brazilian police officers. METHOD: In a cross-sectional sample of active duty officers (n = 212), participants were asked to complete a socio-demographic questionnaire and self-report scales on affective traits, cumulative critical incident exposure, peritraumatic distress and dissociation, PTSD symptoms, and social support. Hierarchical linear regression analysis was conducted to examine predictors of PTSD symptoms. RESULTS: Variables related to negative affect, job duration, frequency of critical incident exposure, peritraumatic dissociation, and lack of social support remained significant in the final model and explained 55 percent of the variance in PTSD symptoms. When interaction terms were evaluated, a synergistic effect between negative affect and peritraumatic dissociation was found. CONCLUSIONS: The risk factors found in this study provide clues on how to elaborate primary prevention strategies regarding PTSD symptoms in police officers. Such initiatives may lessen the impact of repeated exposure to traumatic events on police officers over the course of their careers.

INTRODUÇÃO: A exposição a eventos traumáticos é uma condição necessária, porém não única, para o desenvolvimento de transtorno de estresse pós-traumático (TEPT). Fatores individuais pré, peri e pós-trauma exercem impacto sobre a gravidade dos sintomas. O objetivo do presente estudo é determinar os fatores de risco para o desenvolvimento de sintomas de TEPT em policiais brasileiros. MÉTODO: Uma amostra transversal de policiais em atividade (n = 212) foi convidada a responder um questionário sóciodemográfico e escalas autoaplicáveis sobre afeto positivo e negativo, frequência de incidentes críticos, sofrimento e dissociação peritraumáticos, sintomas de TEPT e apoio social. Regressão linear hierárquica foi utilizada para avaliar fatores de risco. RESULTADOS: Afeto negativo, tempo de trabalho, frequência de exposição a eventos traumáticos, dissociação peritraumática e apoio social diminuído permaneceram no modelo final e explicaram 55 por cento das variações dos sintomas de TEPT. Foi observado efeito sinérgico entre dissociação peritraumática e afeto negativo. CONCLUSÃO: Baseados nos achados os autores discutem estratégias de prevenção que visam diminuir o impacto da exposição a eventos traumáticos em policiais ao longo de suas carreiras.

Evaluation of the emotional peritraumatic response: transcultural adaptation of the Peritraumatic Distress Inventory into Portuguese

Objetivo: Traduzir e determinar a equivalência semântica da Peritraumatic Distress Inventory (PDI) para o Português. Métodos: A versão da escala PDI em português foi ralizada em quatro etapas: tradução, retradução, apreciação formal de equivalência semântica e pré-teste na população-alvo de 22 policiais militares. Uma fase adicional incluiu a análise da equivalência semântica por um dos autores da escala original. Resultados: A versão T1 e a retradução B1 obtiveram maiores escores entre ambos os avaliadores, atingindo notas máximas em 13 dos 15 itens. A população-alvo consistiu em 22 policiais militares (17 homens e 5 mulheres) sem queixas psiquiátricas. A média de idade foi de 33,9 (+- 4,63) anos e todos tinham o ensino médio completo. A população-alvo compreendeu todos os itens da PDI em português e o tempo médio de resposta da escala foi de 90 (+- 10,48) segundos. Conclusões: Este trabalho torna disponível em português a PDI, a primeira escala que avalia objetivamente o critério A2 para o diagnóstico do transtorno de estresse pós-traumático. As propriedades psicométricas da PDI em português devem ser estudadas posteriormente.