Confirmatory test of two factors and four subtypes of bipolar disorder based on lifetime psychiatric co-morbidity

Exploring intra-diagnosis heterogeneity and inter-diagnosis commonality in genetic architectures of bipolar disorders: association of polygenic risks of major psychiatric illnesses and lifetime phenotype dimensions

BACKGROUND

Bipolar disorder (BD) shows heterogeneous illness presentation both cross-sectionally and longitudinally. This phenotypic heterogeneity might reflect underlying genetic heterogeneity. At the same time, overlapping characteristics between BD and other psychiatric illnesses are observed at clinical and biomarker levels, which implies a shared biological mechanism between them. Incorporating these two issues in a single study design, this study investigated whether phenotypically heterogeneous subtypes of BD have a distinct polygenic basis shared with other psychiatric illnesses.

METHODS

Six lifetime phenotype dimensions of BD identified in our previous study were used as target phenotypes. Associations between these phenotype dimensions and polygenic risk scores (PRSs) of major psychiatric illnesses from East Asian (EA) and other available populations were analyzed.

RESULTS

Each phenotype dimension showed a different association pattern with PRSs of mental illnesses. PRS for EA schizophrenia showed a significant negative association with the cyclicity dimension (p = 0.044) but a significant positive association with the psychotic/irritable mania dimension (p = 0.001). PRS of EA major depressive disorder demonstrated a significant negative association with the elation dimension (p = 0.003) but a significant positive association with the comorbidity dimension (p = 0.028).

CONCLUSION

This study demonstrates that well-defined phenotype dimensions of lifetime-basis in BD have distinct genetic risks shared with other major mental illnesses. This finding supports genetic heterogeneity in BD and suggests a pleiotropy among BD subtypes and other psychiatric disorders beyond BD. Further genomic analyses adopting deep phenotyping across mental illnesses in ancestrally diverse populations are warranted to clarify intra-diagnosis heterogeneity and inter-diagnoses commonality issues in psychiatry.

Latent class analysis of bipolar disorder symptoms and suicidal ideation and behaviors

Individuals with bipolar disorder are at increased risk of dying by suicide compared to healthy controls and those with unipolar depression. Previous studies show that depressive symptoms and mixed episodes of mania and depression are related to suicide. However, most of these studies adopt a variable-centered approach to understanding how specific symptoms relate to suicidal ideation, without addressing how these symptoms and symptom profiles relate to suicidal behaviors.

OBJECTIVES

Using latent class analysis, this study adopts a person-centered approach to examine whether subtypes of patients with bipolar disorder differ in their levels of suicidal ideation and behaviors.

METHODS

A total of 150 patients from a behavioral health outpatient clinic were recruited. Latent classes were generated based on self reports of their depressive and manic symptoms.

RESULTS

Five classes of patients with bipolar disorder were identified, namely, a minimal symptom, mania, moderately depressed, severely depressed, and mixed depression-mania subtypes. Those in the severely depressed and mixed depression-mania groups reported significantly higher levels of suicidal ideation and behaviors compared to the other groups.

CONCLUSIONS

Our findings provide further support for the strong relationship between depressive symptoms and suicidality. These findings are significant as they shed light on the different suicide risk profiles among a heterogenous group of patients with bipolar disorder. Name of clinical trial: Suicidal Behavior in Patients Diagnosed with Bipolar Disorder: The Roles of Biological and Childhood and Adult Environmental Risk Factors. ClinicalTrials.gov Identifier: NCT02604277.

Psychopathologic structure of bipolar disorders: exploring dimensional phenotypes, their relationships, and their associations with bipolar I and II disorders

BACKGROUND

Given its diverse disease courses and symptom presentations, multiple phenotype dimensions with different biological underpinnings are expected with bipolar disorders (BPs). In this study, we aimed to identify lifetime BP psychopathology dimensions. We also explored the differing associations with bipolar I (BP-I) and bipolar II (BP-II) disorders.

METHODS

We included a total of 307 subjects with BPs in the analysis. For the factor analysis, we chose six variables related to clinical courses, 29 indicators covering lifetime symptoms of mood episodes, and 6 specific comorbid conditions. To determine the relationships among the identified phenotypic dimensions and their effects on differentiating BP subtypes, we applied structural equation modeling.

RESULTS

We selected a six-factor solution through scree plot, Velicer's minimum average partial test, and face validity evaluations; the six factors were cyclicity, depression, atypical vegetative symptoms, elation, psychotic/irritable mania, and comorbidity. In the path analysis, five factors excluding atypical vegetative symptoms were associated with one another. Cyclicity, depression, and comorbidity had positive associations, and they correlated negatively with psychotic/irritable mania; elation showed positive correlations with cyclicity and psychotic/irritable mania. Depression, cyclicity, and comorbidity were stronger in BP-II than in BP-I, and they contributed significantly to the distinction between the two disorders.

CONCLUSIONS

We identified six phenotype dimensions; in addition to symptom features of manic and depressive episodes, various comorbidities and high cyclicity constructed separate dimensions. Except for atypical vegetative symptoms, all factors showed a complex interdependency and played roles in discriminating BP-II from BP-I.

Confirmatory Latent Class Analysis

Most applications of person-centered methodologies have relied on data-driven approaches to class enumeration. As person-centered analyses grow in popularity within organizational research, confirmatory approaches may be sought to provide more stringent theoretical tests and to formalize replication efforts. Confirmatory latent class analysis (LCA) is achieved through placement of modeling constraints, yet there is variation in the types of potential constraints and a lack of standardization in evaluating model fit in published work. This article provides a comprehensive framework for operationalizing model constraints and demonstrates confirmatory LCA via two illustrations: (a) a dual sample approach ( n = 1,366 and n = 1,367 in exploratory and validation samples, respectively) and (b) confirmatory testing of a hypothesized latent class structure ( n = 1,483). We depict operationalization of threshold boundary and/or equality constraints under both illustrations to generate a confirmatory latent class structure, and explain methods of model evaluation and comparison to alternative models. The confirmatory model was well supported under the dual sample approach, and partially supported under the hypothesis-driven approach. We discuss decision making at various points of model estimation and end with future methodological developments.

Latent class analysis shows that paediatricians' opinions about the advanced resuscitation of extremely preterm infants were diverse and influenced by personal beliefs

AIM

The aim of this study was to survey paediatricians, who taught neonatal resuscitation in Brazil, about when they would apply advanced resuscitation in the delivery room for newborn infants born at 23-26 weeks of gestational age.

METHODS

This cross-sectional study focused on an electronic questionnaire that was sent to paediatricians who acted as instructors for the Brazilian Neonatal Resuscitation Program from December 2011 to September 2013. The primary outcome was the gestational age at which the respondent would apply advanced resuscitation in the delivery room. Latent class analysis identified the profiles of the instructors, and logistic regression identified the variables associated with belonging to one of the derived classes.

RESULTS

The 560 (82%) instructors who agreed to participate fell into three latent classes: pro-resuscitation, intermediate and pro-limitation, with high, intermediate and low probabilities of performing advanced resuscitation in neonates born at 23-26 weeks. In the multivariate model, group membership was associated with the paediatrician's age, years of practice and personal importance of religion and the patient's birthweight, future quality of life and probability of death.

CONCLUSION

The opinions of paediatricians performing advanced resuscitation on extremely preterm infants in the delivery room were diverse and influenced by personal beliefs.

Summaries of plenary and selected symposia sessions at the XXIV World Congress of Psychiatric Genetics; Jerusalem, Israel; 30 October 2016-3 November 2016

The XXII World Congress of Psychiatric Genetics, sponsored by the International Society of Psychiatric Genetics, took place in Jerusalem, Israel, from 30 October 2016 to 3 November 2016. A total of 372 participants gathered to discuss the latest findings in the field. The following report was written by early career investigator travel awardees, and student and postdoctoral attendees. Each was assigned one or more sessions as a rapporteur. This manuscript represents topics covered in most, but not all of the presentations during the conference, and contains some of the major notable new findings reported.

Rapporteur summaries of plenary, symposia, and oral sessions from the XXIIIrd World Congress of Psychiatric Genetics Meeting in Toronto, Canada, 16-20 October 2015

The XXIIIrd World Congress of Psychiatric Genetics meeting, sponsored by the International Society of Psychiatric Genetics, was held in Toronto, ON, Canada, on 16-20 October 2015. Approximately 700 participants attended to discuss the latest state-of-the-art findings in this rapidly advancing and evolving field. The following report was written by trainee travel awardees. Each was assigned one session as a rapporteur. This manuscript represents the highlights and topics that were covered in the plenary sessions, symposia, and oral sessions during the conference, and contains major notable and new findings.

Data-driven classification of bipolar I disorder from longitudinal course of mood

The Diagnostic and Statistical Manual of Mental Disorder (DSM) classification of bipolar disorder defines categories to reflect common understanding of mood symptoms rather than scientific evidence. This work aimed to determine whether bipolar I can be objectively classified from longitudinal mood data and whether resulting classes have clinical associations. Bayesian nonparametric hierarchical models with latent classes and patient-specific models of mood are fit to data from Longitudinal Interval Follow-up Evaluations (LIFE) of bipolar I patients (N=209). Classes are tested for clinical associations. No classes are justified using the time course of DSM-IV mood states. Three classes are justified using the course of subsyndromal mood symptoms. Classes differed in attempted suicides (P=0.017), disability status (P=0.012) and chronicity of affective symptoms (P=0.009). Thus, bipolar I disorder can be objectively classified from mood course, and individuals in the resulting classes share clinical features. Data-driven classification from mood course could be used to enrich sample populations for pharmacological and etiological studies.

Characteristics of Bipolar I patients grouped by externalizing disorders

BACKGROUND

Bipolar disorder co-occurs with a number of disorders with externalizing features. The aim of this study is to determine whether Bipolar I (BPI) subjects with comorbid externalizing disorders and a subgroup with externalizing symptoms prior to age 15 have different clinical features than those without externalizing disorders and whether these could be attributed to specific genetic variations.

METHODS

A large cohort (N=2505) of Bipolar I subjects was analyzed. Course of illness parameters were compared between an Externalizing Group, an Early-Onset Subgroup and a Non-Externalizing Group in the Discovery sample (N=1268). Findings were validated using an independent set of 1237 BPI subjects (Validation sample). Genetic analyses were carried out.

RESULTS

Subjects in the Externalizing Group (and Early-Onset Subgroup) tended to have a more severe clinical course, even in areas specifically related to mood disorder such as cycling frequency and rapid mood switching. Regression analysis showed that the differences are not completely explainable by substance use. Genetic analyses identified nominally associated SNPs; calcium channel genes were not enriched in the gene variants identified.

LIMITATIONS

Validation in independent samples is needed to confirm the genetic findings in the present study.

CONCLUSIONS

Our findings support the presence of an externalizing disorder subphenotype within BPI with greater severity of mood disorder and possible specific genetic features.