Further Evidence for a Dimensional Latent Structure of Health Anxiety: Taxometric Analyses of the Whiteley Index Based on Two German Representative Samples

Health anxiety is an intricate part of illness anxiety and somatic symptom disorder. Based on convenience samples, two out of three available studies indicate that it is a dimensional rather than a categorical construct. Using two representative datasets, this study investigates whether previous results can be clarified. Conventional taxometric analyses as well as comparison curve fit indices (CCFI) profile analyses (MAMBAC and MAXSLOPE procedures) were calculated with two datasets of the German adult population assessing the Whiteley Index (WI-14, N = 2,072; WI-7, N = 2,498). Mean CCFIs indicated a dimensional structure for both the WI-7 (mean CCFI = 0.42, mean CCFI profile = 0.40) and the WI-14 (mean CCFI = 0.44, mean CCFI profile = 0.32). The results support and extend previous findings by strongly suggesting a dimensional distribution of health anxiety in the general population. Implications for research and practice comprise the adoption of a dimensional description of psychopathology as well as transdiagnostic treatment approaches.

Evidence for the taxonic latent structure for DSM-5 intermittent explosive disorder in adults

BACKGROUND

Identification of individuals with clinically significant aggressive behavior is critical for the prevention and management of human aggressive behavior. A previous population-based taxometric study reported that the Diagnostic and Statistical Manual of Mental Disorders-4th Edition (DSM-IV) intermittent explosive disorder (IED) belongs to its own discrete class (taxon) rather than existing along a continuum.

METHODS

This study sought to extend previous population-based findings in a clinical research sample of adults with DSM-5 IED (n = 346), adults with non-aggressive DSM-5 disorders (n = 293), and adults without any DSM-5 disorder (n = 174), using standardized assessments of DSM-5 diagnoses, aggression, and other related measures not available in past studies.

RESULTS

Analyses revealed a taxonic latent structure that overlapped with the DSM-5 diagnosis of IED. Within the sample, taxon group members had higher scores on a variety of measures of psychopathology than did the complement members of the sample. Comorbidity of other diagnoses with IED did not affect these results.

CONCLUSION

These findings support the proposition that DSM-5 IED represents a distinct behavioral disorder rather than the severe end of an aggressive behavior continuum.

A Latent Structure Analysis of Cognitive Vulnerability to Depression in Adolescence

Whether cognitive vulnerability to depression exists along a continuum of severity or as a qualitatively discrete phenomenological entity has direct bearing on theoretical formulations of risk for depression and clinical risk assessment. This question is of particular relevance to adolescence, given that cognitive vulnerability appears to coalesce and rates of depression begin to rise markedly during this period of development. Although a dimensional view is often assumed, it is necessary to submit this assumption to direct empirical evaluation. Taxometric analysis is a family of statistical techniques developed directly to test such assumptions. The present study applied taxometric methods to address this question in a community sample of early adolescents (n = 485), drawing on three indices of cognitive vulnerability to depression (i.e., negative inferential style, ruminative response style, self-referent information processing). The results of three taxometric analyses (i.e., mean above minus below a cut [MAMBAC], maximum eigenvalue [MAXEIG], and latent mode [L-Mode]) were consistent in unambiguously supporting a dimensional conceptualization of this construct. The latent structure of the tested indices of cognitive vulnerability to depression in adolescence appears to exist along a continuum of severity rather than as a discrete clinical entity.

The classification of eating disorders in China: A categorical model or a dimensional model

OBJECTIVE

According to the ICD-10 and DSM-5, eating disorders (EDs) are classified using a categorical model that assumes the subtypes are qualitatively different from one another. However, it is still intensely debated that a dimensional model is more suitable. The aim of this study is to examine whether EDs have a categorical or dimensional latent structure using a sample of Chinese ED patients.

METHOD

The sample included 322 patients, diagnosed with an ED from 2010 to 2017 in the Shanghai Mental Health Center, and comparison participants (N = 850), recruited from undergraduate students in one university in Shanghai. Participants were evaluated with the Eating Disorder Inventory-2 (EDI-2) questionnaire and another questionnaire developed by the researchers. Three taxometric procedures (MAXimum EIGenvalue [MAXEIG], latent-mode factor analysis [L-Mode], and Mean Above Minus Below A Cut [MAMBAC]) were applied, respectively, to analyze the patients' clinical symptoms data.

RESULTS

Patients were divided into three groups according to their clinical diagnosis. The plots of the three taxometric analysis procedures supported the categorical construct in anorexia nervosa, binge-eating/purging group, and bulimia nervosa group. The Comparison Curve Fit Indices of the MAXEIG, L-Mode, and MAMBAC procedures were 0.694, 0.709, 0.704 in the AN-BP group and 0.727, 0.67, 0.62 in the BN group, respectively, which also support the categorical construct.

DISCUSSION

The results support two distinct classes of ED subtypes among Chinese sample. Further work on applying hybrid model in analysis has been discussed.

The latent structure of the functional dyspepsia symptom complex: a taxometric analysis

OBJECTIVES

Rome III introduced a subdivision of functional dyspepsia (FD) into postprandial distress syndrome and epigastric pain syndrome, characterized by early satiation/postprandial fullness, and epigastric pain/burning, respectively. However, evidence on their degree of overlap is mixed. We aimed to investigate the latent structure of FD to test whether distinguishable symptom-based subgroups exist.

METHODS

Consecutive tertiary care Rome II FD patients completed the dyspepsia symptom severity scale. Confirmatory factor analysis (CFA) was used to compare the fit of a single factor model, a correlated three-factor model based on Rome III subgroups and a bifactor model consisting of a general FD factor and orthogonal subgroup factors. Taxometric analyses were subsequently used to investigate the latent structure of FD.

KEY RESULTS

Nine hundred and fifty-seven FD patients (71.1% women, age 41 ± 14.8) participated. In CFA, the bifactor model yielded a significantly better fit than the two other models (χ² difference tests both p < 0.001). All symptoms had significant loadings on both the general and the subgroup-specific factors (all p < 0.05). Somatization was associated with the general (r = 0.72, p < 0.01), but not the subgroup-specific factors (all r < 0.13, p > 0.05). Taxometric analyses supported a dimensional structure of FD (all CCFI<0.38).

CONCLUSIONS AND INFERENCES

We found a dimensional rather than categorical latent structure of the FD symptom complex in tertiary care. A combination of a general dyspepsia symptom reporting factor, which was associated with somatization, and symptom-specific factors reflecting the Rome III subdivision fitted the data best. This has implications for classification, pathophysiology, and treatment of FD.

Do recognizable lifetime eating disorder phenotypes naturally occur in a culturally asian population? A combined latent profile and taxometric approach

BACKGROUND

We examined whether empirically derived eating disorder (ED) categories in Hong Kong Chinese patients (N = 454) would be consistent with recognizable lifetime ED phenotypes derived from latent structure models of European and American samples.

METHOD

We performed latent profile analysis (LPA) using indicator variables from data collected during routine assessment, and then applied taxometric analysis to determine whether latent classes were qualitatively versus quantitatively distinct.

RESULTS

Latent profile analysis identified four classes: (i) binge/purge (47%); (ii) non-fat-phobic low-weight (34%); (iii) fat-phobic low-weight (12%); and (iv) overweight disordered eating (6%). Taxometric analysis identified qualitative (categorical) distinctions between the binge/purge and non-fat-phobic low-weight classes, and also between the fat-phobic and non-fat-phobic low-weight classes. Distinctions between the fat-phobic low-weight and binge/purge classes were indeterminate.

CONCLUSION

Empirically derived categories in Hong Kong showed recognizable correspondence with recognizable lifetime ED phenotypes. Although taxometric findings support two distinct classes of low weight EDs, LPA findings also support heterogeneity among non-fat-phobic individuals.

On the latent structure of problem gambling: a taxometric analysis

AIMS

To test whether problem gambling is a categorical or dimensional disorder on the basis of two problem gambling assessments. This distinction discriminates between two different conceptualizations of problem gambling: one that problem gambling is defined by its addictive properties, the other that it is a continuum of harm.

METHOD

Using The British Gambling Prevalence Survey 2010, a nationally representative sample of the United Kingdom conducted by the National Centre for Social Research, five different taxometric analyses were carried out on cases from two problem gambling screens: the Problem Gambling Severity Index (PGSI) and a measure derived from the DSM-IV Pathological Gambling criteria. Two further analyses were conducted on the total scores for these measures.

RESULTS

There was strong evidence that both scales were measuring a categorical construct. Fit indices consistently supported a categorical interpretation [comparison curve fit index (CCFI) > 0.6]. The PGSI analysis indicated the presence of a taxon (CCFIs = 0.633, 0.756). The analysis conducted on the adapted DSM-IV criteria indicated stronger quantitative support for a taxon (CCFIs = 0.717, 0.811 and 0.756) but items probing a loss of control were inconsistent. The taxometric analyses of both scales support a categorical interpretation (CCFIs = 0.628, 0.567), but extreme caution should be used due to high nuisance covariance.

CONCLUSIONS

Two problem gambling screens (the Problem Gambling Severity Index and a measure derived from the DSM-IV Pathological Gambling criteria) appear to measure a categorical construct that taps into a categorical, loss of control model of problem gambling. There is some evidence that the two screens measure different aspects of an addiction construct.

Taxometric analysis of DSM-IV and DSM-5 alcohol use disorders

BACKGROUND

With preparations currently being made for the Diagnostic and Statistical Manual of Mental Disorders-5th Edition (DSM-5), one prominent issue to resolve is whether alcohol use disorders are better represented as discrete categorical entities or as a dimensional construct. The purpose of this study was to investigate the latent structure of DSM-4th edition (DSM-IV) and proposed DSM-5 alcohol use disorders.

METHODS

The study used the Wave 2 National Epidemiologic Survey on Alcohol and Related Conditions (NESARC) to conduct taxometric analyses of DSM-IV and DSM-5 alcohol use disorders defined by different thresholds to determine the taxonic or dimensional structure underlying the disorders.

RESULTS

DSM-IV and DSM-5 alcohol abuse and dependence criteria with 3+ thresholds demonstrated a dimensional structure. Corresponding thresholds with 4+ criteria were clearly taxonic, as were thresholds defined by cut-offs of 5+ and 6+ criteria.

CONCLUSIONS

DSM-IV and DSM-5 alcohol use disorders demonstrated a hybrid taxonic-dimensional structure. That is, DSM-IV and DSM-5 alcohol use disorders may be taxonically distinct compared to no disorder if defined by a threshold of 4 or more criteria. However, there may be dimensional variation remaining among non-problematic to subclinical cases. A careful and systematic program of structural research using taxometric and psychometric procedures is warranted.

The latent structure of attention deficit/hyperactivity disorder in an adult sample

The vast majority of studies that have examined the latent structure of attention deficit/hyperactivity disorder (ADHD) in children and adolescents have concluded that ADHD has a dimensional latent structure. In other words, ADHD symptomatology exists along a continuum and there is no natural boundary or qualitative distinction (i.e., taxon) separating youth with ADHD from those with subclinical inattention or hyperactivity/impulsivity problems. Although adult ADHD appears to be less prevalent than ADHD in youth (which could suggest a more severe adult ADHD taxon), researchers have yet to examine the latent structure of ADHD in adults. The present study used a sample (N = 600) of adults who completed a self-report measure of ADHD symptoms. The taxometric analyses revealed a dimensional latent structure for inattention, hyperactivity/impulsivity, and ADHD. These findings are consistent with previous taxometric studies that examined ADHD in children and adolescents, and with contemporary polygenic and multifactorial models of ADHD.

Seeking verisimilitude in a class: a systematic review of evidence that the criterial clinical symptoms of schizophrenia are taxonic

This review examines whether there is evidence that the criterion symptoms of Diagnostic and Statistical Manual of Mental Disorders (Fourth Edition) (DSM-IV) schizophrenia are taxonic--that schizophrenia is not part of a single distribution of normality. Two taxometric methods, coherent cut kinetics (CCK) and latent variable modeling (LVM), are demonstrated to be sensitive to latent classes and, therefore, were regarded as providing relevant statistical evidence. A systematic literature search identified 24 articles describing analyses of 28 participant cohorts in which CCK or LVM methods were used with one or more criterion symptoms of schizophrenia. Virtually all analyses yielded results that, on first impression, favored taxonic over dimensional interpretations of the latent structure of schizophrenia. However, threats to the internal and external validity of these studies--including biased or inadequate analyses, violation of statistical assumptions, inadequate indicator screening, and the introduction of systematic error through recruitment and sampling--critically undermine this body of work. Uncertainties about the potential effects of perceptual biases, unimodal assessment, and item parceling are also identified, as are limitations in seeking to validate classes with single or double dissociations of outcomes. We conclude that there is no reason to seriously doubt a single-distribution model of schizophrenia because there is no evidence that provides a serious test of this null hypothesis. A second fundamental question remains outstanding: is schizophrenia truly a group of schizophrenias, with taxonic divisions separating its types? We make design and analysis suggestions for future research addressing these questions.

THLASPI CAERULESCENS J. & C. PRESL. (T. ALPESTRE L.) IN BRITAIN

Thlaspi caerulescens J. & C. Presl. (T. alpestre L.) has a restricted and disjunct distribution in Britain. Both on natural and mine sites it is confined to soils contaminated by lead and zinc. Morphological variation occurs both regionally and locally but there is no support from a taxometric cluster analysis for the taxonomic recognition of variants. In experiment the index of zinc tolerance of plants raised from seed was positively correlated with the concentration of zinc in the soils from which the seed parents originated. The distribution of T. caerulescens is discussed in relation to morphological and physiological variation between populations.