Progress in achieving quantitative classification of psychopathology

Shortcomings of approaches to classifying psychopathology based on expert consensus have given rise to contemporary efforts to classify psychopathology quantitatively. In this paper, we review progress in achieving a quantitative and empirical classification of psychopathology. A substantial empirical literature indicates that psychopathology is generally more dimensional than categorical. When the discreteness versus continuity of psychopathology is treated as a research question, as opposed to being decided as a matter of tradition, the evidence clearly supports the hypothesis of continuity. In addition, a related body of literature shows how psychopathology dimensions can be arranged in a hierarchy, ranging from very broad "spectrum level" dimensions, to specific and narrow clusters of symptoms. In this way, a quantitative approach solves the "problem of comorbidity" by explicitly modeling patterns of co-occurrence among signs and symptoms within a detailed and variegated hierarchy of dimensional concepts with direct clinical utility. Indeed, extensive evidence pertaining to the dimensional and hierarchical structure of psychopathology has led to the formation of the Hierarchical Taxonomy of Psychopathology (HiTOP) Consortium. This is a group of 70 investigators working together to study empirical classification of psychopathology. In this paper, we describe the aims and current foci of the HiTOP Consortium. These aims pertain to continued research on the empirical organization of psychopathology; the connection between personality and psychopathology; the utility of empirically based psychopathology constructs in both research and the clinic; and the development of novel and comprehensive models and corresponding assessment instruments for psychopathology constructs derived from an empirical approach.

Self-report captures 27 distinct categories of emotion bridged by continuous gradients

Emotions are centered in subjective experiences that people represent, in part, with hundreds, if not thousands, of semantic terms. Claims about the distribution of reported emotional states and the boundaries between emotion categories-that is, the geometric organization of the semantic space of emotion-have sparked intense debate. Here we introduce a conceptual framework to analyze reported emotional states elicited by 2,185 short videos, examining the richest array of reported emotional experiences studied to date and the extent to which reported experiences of emotion are structured by discrete and dimensional geometries. Across self-report methods, we find that the videos reliably elicit 27 distinct varieties of reported emotional experience. Further analyses revealed that categorical labels such as amusement better capture reports of subjective experience than commonly measured affective dimensions (e.g., valence and arousal). Although reported emotional experiences are represented within a semantic space best captured by categorical labels, the boundaries between categories of emotion are fuzzy rather than discrete. By analyzing the distribution of reported emotional states we uncover gradients of emotion-from anxiety to fear to horror to disgust, calmness to aesthetic appreciation to awe, and others-that correspond to smooth variation in affective dimensions such as valence and dominance. Reported emotional states occupy a complex, high-dimensional categorical space. In addition, our library of videos and an interactive map of the emotional states they elicit (https://s3-us-west-1.amazonaws.com/emogifs/map.html) are made available to advance the science of emotion.

Psychosis genetics: modeling the relationship between schizophrenia, bipolar disorder, and mixed (or "schizoaffective") psychoses

As a result of improving technologies and greatly increased sample sizes, the last 2 years has seen unprecedented advances in identification of specific genetic risk factors for psychiatric phenotypes. Strong genetic associations have been reported at common polymorphisms within ANK3 and CACNA1C in bipolar disorder and ZNF804A in schizophrenia and a relatively specific association between common variation in GABA(A) receptor genes and cases with features of both bipolar disorder and schizophrenia. Further, the occurrence of rare copy number variants (CNVs) has been shown to be increased in schizophrenia compared with controls. These emerging data provide a powerful resource for exploring the relationship between psychiatric phenotypes and can, and should, be used to inform conceptualization, classification, and diagnosis in psychiatry. It is already clear that, in general, genetic associations are not specific to one of the traditional diagnostic categories. For example, variation at ZNF804A is associated with risk of both bipolar disorder and schizophrenia, and some rare CNVs are associated with risk of autism and epilepsy as well as schizophrenia. These data are not consistent with a simple dichotomous model of functional psychosis and indicate the urgent need for moves toward approaches that (a) better represent the range of phenotypic variation seen in the clinical population and (b) reflect the underlying biological variation that gives rise to the phenotypes. We consider the implications for models of psychosis and the importance of recognizing and studying illness that has prominent affective and psychotic features. We conclude that if psychiatry is to translate the opportunities offered by new research methodologies, we must finally abandon a 19th-century dichotomy and move to a classificatory approach that is worthy of the 21st century.

Annual research review: re-thinking the classification of autism spectrum disorders

BACKGROUND

The nosology of autism spectrum disorders (ASD) is at a critical point in history as the field seeks to better define dimensions of social-communication deficits and restricted/repetitive behaviors on an individual level for both clinical and neurobiological purposes. These different dimensions also suggest an increasing need for quantitative measures that accurately map their differences, independent of developmental factors such as age, language level and IQ.

METHOD

Psychometric measures, clinical observation as well as genetic, neurobiological and physiological research from toddlers, children and adults with ASD are reviewed.

RESULTS

The question of how to conceptualize ASDs along dimensions versus categories is discussed within the nosology of autism and the proposed changes to the DSM-5 and ICD-11. Differences across development are incorporated into the new classification frameworks.

CONCLUSIONS

It is crucial to balance the needs of clinical practice in ASD diagnostic systems, with neurobiologically based theories that address the associations between social-communication and restricted/repetitive dimensions in individuals. Clarifying terminology, improving description of the core features of ASD and other dimensions that interact with them and providing more valid and reliable ways to quantify them, both for research and clinical purposes, will move forward both practice and science.

The Development of the ICD-11 Classification of Personality Disorders: An Amalgam of Science, Pragmatism, and Politics

The nomenclature of personality disorders in the 11th revision of the International Classification of Diseases and Related Health Problems represents the most radical change in the classification history of personality disorders. A dimensional structure now replaces categorical description. It was argued by the Working Group that only a dimensional system was consistent with the empirical evidence and, in the spirit of clinical utility, the new system is based on two steps. The first step is to assign one of five levels of severity, and the second step is to assign up to five prominent domain traits. There was resistance to this structure from those who feel that categorical diagnosis, particularly of borderline personality disorder, should be retained. After lengthy discussion, described in detail here, there is now an option for a borderline pattern descriptor to be selected as a diagnostic option after severity has been determined.

Confirmatory factor analysis of the Oral Health Impact Profile

Previous exploratory analyses suggest that the Oral Health Impact Profile (OHIP) consists of four correlated dimensions and that individual differences in OHIP total scores reflect an underlying higher-order factor. The aim of this report is to corroborate these findings in the Dimensions of Oral Health-Related Quality of Life (DOQ) Project, an international study of general population subjects and prosthodontic patients. Using the project's Validation Sample (n = 5022), we conducted confirmatory factor analyses in a sample of 4993 subjects with sufficiently complete data. In particular, we compared the psychometric performance of three models: a unidimensional model, a four-factor model and a bifactor model that included one general factor and four group factors. Using model-fit criteria and factor interpretability as guides, the four-factor model was deemed best in terms of strong item loadings, model fit (RMSEA = 0·05, CFI = 0·99) and interpretability. These results corroborate our previous findings that four highly correlated factors - which we have named Oral Function, Oro-facial Pain, Oro-facial Appearance and Psychosocial Impact - can be reliably extracted from the OHIP item pool. However, the good fit of the unidimensional model and the high interfactor correlations in the four-factor solution suggest that OHRQoL can also be sufficiently described with one score.

Hierarchical models of psychopathology: empirical support, implications, and remaining issues

There is an ongoing revolution in psychology and psychiatry that will likely change how we conceptualize, study and treat psychological problems.- Many theorists now support viewing psychopathology as consisting of continuous dimensions rather than discrete diagnostic categories. Indeed, recent papers have proposed comprehensive taxonomies of psychopathology dimensions to replace the DSM and ICD taxonomies of categories. The proposed dimensional taxonomies, which portray psychopathology as hierarchically organized correlated dimensions, are now well supported at phenotypic levels. Multiple studies show that both a general factor of psychopathology at the top of the hierarchy and specific factors at lower levels predict different functional outcomes. Our analyses of data on a large representative sample of child and adolescent twins suggested the causal hypothesis that phenotypic correlations among dimensions of psychopathology are the result of many familial influences being pleiotropic. That is, most genetic variants and shared environmental factors are hypothesized to non-specifically influence risk for multiple rather than individual dimensions of psychopathology. In contrast, person-specific experiences tend to be related to individual dimensions. This hierarchical causal hypothesis has been supported by both large-scale family and molecular genetic studies. Current research focuses on three issues. First, the field has not settled on a preferred statistical model for studying the hierarchy of causes and phenotypes. Second, in spite of encouraging progress, the neurobiological correlates of the hierarchy of dimensions of psychopathology are only partially described. Third, although there are potentially important clinical implications of the hierarchical model, insufficient research has been conducted to date to rec-ommend evidence-based clinical practices.

Exploratory factor analysis of the Oral Health Impact Profile

Although oral health-related quality of life (OHRQoL) as measured by the Oral Health Impact Profile (OHIP) is thought to be multidimensional, the nature of these dimensions is not known. The aim of this report was to explore the dimensionality of the OHIP using the Dimensions of OHRQoL (DOQ) Project, an international study of general population subjects and prosthodontic patients. Using the project's Learning Sample (n = 5173), we conducted an exploratory factor analysis on the 46 OHIP items not specifically referring to dentures for 5146 subjects with sufficiently complete data. The first eigenvalue (27·0) of the polychoric correlation matrix was more than ten times larger than the second eigenvalue (2·6), suggesting the presence of a dominant, higher-order general factor. Follow-up analyses with Horn's parallel analysis revealed a viable second-order, four-factor solution. An oblique rotation of this solution revealed four highly correlated factors that we named Oral Function, Oro-facial Pain, Oro-facial Appearance and Psychosocial Impact. These four dimensions and the strong general factor are two viable hypotheses for the factor structure of the OHIP.

Understanding Psychopathology: Melding Behavior Genetics, Personality, and Quantitative Psychology to Develop an Empirically Based Model

Research on psychopathology is at a historical crossroads. New technologies offer the promise of lasting advances in our understanding of the causes of human psychological suffering. Making the best use of these technologies, however, requires an empirically accurate model of psychopathology. Much current research is framed by the model of psychopathology portrayed in current versions of the Diagnostic and Statistical Manual of Mental Disorders (DSM; American Psychiatric Association, 2000). Although the modern DSMs have been fundamental in advancing psychopathology research, recent research also challenges some assumptions made in the DSM-for example, the assumption that all forms of psychopathology are well conceived of as discrete categories. Psychological science has a critical role to play in working through the implications of this research and the challenges it presents. In particular, behavior-genetic, personality, and quantitative-psychological research perspectives can be melded to inform the development of an empirically based model of psychopathology that would constitute an evolution of the DSM.

Testing the psychopathology of psychosis: evidence for a general psychosis dimension

BACKGROUND

Psychiatric taxonomists have sometimes argued for a unitary psychosis syndrome and sometimes for a pentagonal model, including 5 diagnostic constructs of positive symptoms, negative symptoms, cognitive disorganization, mania, and depression. This continues to be debated in preparation for impending revisions of the Diagnostic and Statistical Manual of Mental Disorders and the International Classification of Diseases. We aimed to identify general and specific dimensions underlying psychopathological features of psychosis.

METHODS

The samples comprised 309 patients admitted to psychiatric services in the acute phase of their first or second episode of psychosis and 507 patients with enduring psychosis recruited from community mental health teams. Patients' symptoms were assessed on the Positive and Negative Symptom Scale. Analyses compared unitary, pentagonal, and bifactor models of psychosis.

RESULTS

In both samples, a bifactor model including 1 general psychosis factor and, independently, 5 specific factors of positive symptoms, negative symptoms, disorganization, mania, and depression gave the best fit. Scores of general and specific symptom dimensions were differentially associated with phase of illness, diagnosis, social functioning, insight, and neurocognitive functioning.

CONCLUSIONS

The findings provide strong evidence for a general psychosis dimension in both early and enduring psychosis. Findings further allowed for independent formation of specific symptom dimensions. This may inform the current debate about revised classification systems of psychosis.

Synthesizing dimensional and categorical approaches to personality disorders: refining the research agenda for DSM-V Axis II

Personality disorder researchers have long considered the utility of dimensional approaches to diagnosis, signaling the need to consider a dimensional approach for personality disorders in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-V). Nevertheless, a dimensional approach to personality disorders in DSM-V is more likely to succeed if it represents an orderly and logical progression from the categorical system in DSM-IV. With these considerations and opportunities in mind, the authors sought to delineate ways of synthesizing categorical and dimensional approaches to personality disorders that could inform the construction of DSM-V. This discussion resulted in (1) the idea of having a set of core descriptive elements of personality for DSM-V, (2) an approach to rating those elements for specific patients, (3) a way of combining those elements into personality disorder prototypes, and (4) a revised conception of personality disorder as a construct separate from personality traits.

Dimensions and the psychosis phenotype

In this paper, we discuss the conceptual background for including a dimensional component to the DSM V diagnoses for psychoses. We review the evidence for a continuous distribution of psychosis like symptoms in the general population and summarise the research validating the clinical usefulness of psychopathological dimensions. We conclude that diagnostic models using both categorical and dimensional representations of psychosis have better predictive validity than either model independently. Dimensions do not appear to be diagnosis specific so a flexible scoring of dimensions across all psychotic and major affective disorders may be potentially more informative than a system where categorical diagnoses are kept artificially dimension-specific.

Echocardiographic Assessment of the Right Ventricle, from the Conventional Approach to Speckle Tracking and Three-Dimensional Imaging, and Insights into the "Right Way" to Explore the Forgotten Chamber

BACKGROUND

The right ventricle (RV) has an essential function in cardiovascular physiology and pathology. Currently, it is gaining an increasing interest given its recognized role in many cardiovascular conditions. However, echocardiographic assessment of the RV in daily practice is frequently based on qualitative estimation, and it has been regarded as a neglected chamber.

OBJECTIVE

We sought to review and discuss the appropriate approach and latest methods of assessment of the RV by echocardiography.

METHODS

A MEDLINE/Pubmed search was performed, and 55 relevant articles were selected; articles addressing right ventricular assessment by echocardiography, along with the latest recommendations, have been reviewed and discussed.

RESULTS

A RV diameter >42 mm at the base and >35 mm at the mid-cavitary level indicates right ventricular dilatation; a longitudinal myocardial velocity (S') <9.5 mm/s, a tricuspid annular plane systolic excursion <17 mm, and a fractional area change <35% are indices of right ventricular systolic dysfunction. A right ventricular ejection fraction of >45% and an absolute value of global longitudinal strain of >21% reflect normal systolic function. The significance of dp/dt, the right myocardial performance index and isovolumic myocardial acceleration, is also discussed along with the parameters of right ventricular diastolic function. The use of novel echocardiographic approaches, such as three-dimensional echo and speckle tracking imaging, allows practitioners to overcome the challenges encountered with conventional echocardiography.

CONCLUSION

Accurate assessment of the RV by echocardiography yields early detection of cardiac diseases, enhances risk stratification, and allows timely initiation of appropriate therapy.

Reference right atrial dimensions and volume estimation by steady state free precession cardiovascular magnetic resonance

BACKGROUND

Cardiovascular magnetic resonance (CMR) steady state free precession (SSFP) cine sequences with high temporal resolution and improved post-processing can accurately measure RA dimensions. We used this technique to define ranges for normal RA volumes and dimensions normalized, when necessary, to the influence of gender, body surface area (BSA) and age, and also to define the best 2D images-derived predictors of RA enlargement.

METHODS

For definition of normal ranges of RA volume we studied 120 healthy subjects (60 men, 60 women; 20 subjects per age decile from 20 to 80 years), after careful exclusion of cardiovascular abnormality. We also studied 120 patients (60 men, 60 women; age range 20 to 80 years) with a clinical indication for CMR in order to define the best 1D and 2D predictors of RA enlargement. Data were generated from SSFP cine CMR, with 3-dimensional modeling, including tracking of the atrioventricular ring motion and time-volume curves analysis.

RESULTS

In the group of healthy individuals, age influenced RA 2-chamber area and transverse diameter. Gender influenced most absolute RA dimensions and volume. Interestingly, right atrial volumes did not change with age and gender when indexed to body surface area. New CMR normal ranges for RA dimensions were modeled and displayed for clinical use with normalization for BSA and gender and display of parameter variation with age. Finally, the best 2D images-derived independent predictors of RA enlargement were indexed area and indexed longitudinal diameter in the 2-chamber view.

CONCLUSION

Reference RA dimensions and predictors of RA enlargement are provided using state-of-the-art CMR techniques.

Patterns of impaired oral health-related quality of life dimensions

How dental patients are affected by oral conditions can be described with the concept of oral health-related quality of life (OHRQoL). This concept intends to make the patient experience measurable. OHRQoL is multidimensional, and Oral Function, Oro-facial Pain, Oro-facial Appearance and Psychosocial Impact were suggested as its four dimensions and consequently four scores are needed for comprehensive OHRQoL assessment. When only the presence of dimensional impact is measured, a pattern of affected OHRQoL dimensions would describe in a simple way how oral conditions influence the individual. By determining which patterns of impact on OHRQoL dimensions exist in prosthodontic patients and general population subjects, we aimed to identify in which combinations oral conditions' functional, painful, aesthetical and psychosocial impact occurs. Data came from the Dimensions of OHRQoL Project with Oral Health Impact Profile (OHIP)-49 data from 6349 general population subjects and 2999 prosthodontic patients in the Learning Sample (N = 5173) and the Validation Sample (N = 5022). We hypothesised that all 16 patterns of OHRQoL dimensions should occur in these individuals who suffered mainly from tooth loss, its causes and consequences. A dimension was considered impaired when at least one item in the dimension was affected frequently. The 16 possible patterns of impaired OHRQoL dimensions were found in patients and general population subjects in both Learning and Validation Samples. In a four-dimensional OHRQoL model consisting Oral Function, Oro-facial Pain, Oro-facial Appearance and Psychosocial Impact, oral conditions' impact can occur in any combination of the OHRQoL dimensions.

The Multifaceted Nature of Alexithymia - A Neuroscientific Perspective

Neuroscientific studies have mostly employed the 20-item Toronto Alexithymia Scale (TAS-20; Bagby et al., 1994a) for the assessment of alexithymia, a self-report scale that assesses the alexithymia facets difficulty identifying feelings, difficulty describing feelings, and externally oriented thinking. These facets can be considered to capture difficulties in the cognitive processing of emotions associated with alexithymia. However, Nemiah and Sifneos' original conceptualization of alexithymia included also an affective component, a lack of imaginative capacities, which cannot be assessed using the TAS-20. Aiming to capture the entire alexithymia construct, the Bermond-Vorst Alexithymia Questionnaire (BVAQ; Vorst and Bermond, 2001) was developed, a self-report scale which assesses two affective facets (difficulty fantasizing and difficulty emotionalizing) in addition to three cognitive facets. Based on these facets, an affective and a cognitive dimension of alexithymia can be distinguished. By now, several neuroscientific studies have investigated the neural signatures of the different facets and dimensions of alexithymia. Here, I provide an overview of the history of the alexithymia facets and dimensions and review findings provided by functional and structural magnetic resonance imaging (MRI) studies that differentiated between the alexithymia facets and/or its affective and cognitive dimensions. I then provide a synopsis of the current neuroscientific evidence for dissociable substrates of alexithymia facets and dimensions. Finally, the scientific value and clinical implications of these findings are discussed.

Dimensions of oppositionality in a Brazilian community sample: testing the DSM-5 proposal and etiological links

OBJECTIVE

Investigating dimensions of oppositional symptoms may help to explain heterogeneity of etiology and outcomes for mental disorders across development and provide further empirical justification for the DSM-5-proposed modifications of oppositional defiant disorder (ODD). However, dimensions of oppositionality have not previously been tested in samples outside Europe or the United States. In this study, we used a large Brazilian community sample to compare the fit of different models for dimensions of oppositional symptoms; to examine the association of psychiatric diagnoses and symptoms with dimensions of oppositionality; and to examine the associations between dimensions of oppositionality and parental history of mental disorders.

METHOD

A Brazilian community sample of 2,512 children 6 through 12 years old were investigated in this study. Confirmatory factorial analyses were performed to compare the fit of alternative models, followed by linear and logistic regression analyses of associations with psychiatric diagnosis and parental history of psychopathology.

RESULTS

A three-factor model with irritable, headstrong, and hurtful dimensions fitted best. The irritable dimension showed a strong association with emotional disorders in the child (p<.001) and history of depression (p<.01) and suicidality (p<.05) in the mother. The headstrong dimension was uniquely associated with attention-deficit/hyperactivity disorder (ADHD) in the child (p<.001) and with maternal history of ADHD symptoms (p<.05). The hurtful dimension was specifically associated with conduct disorder (p< .05).

CONCLUSIONS

Our findings from a large community sample of Brazilian children support a distinction between dimensions of oppositionality consistent with current DSM-5 recommendations and provide further evidence for etiological distinctions between these dimensions.

Neurobehavioral Traits as Transdiagnostic Predictors of Clinical Problems

The National Institute of Mental Health Research Domain Criteria initiative (Insel et al., 2010) calls for a focus on biologically meaningful dimensional constructs in the study of clinical problems. Examples are needed of how Research Domain Criteria constructs can be linked to clinical problems. We examined how two such constructs, threat sensitivity (THT+) and weak inhibitory control (INH-), operationalized using scale measures of fear/fearlessness and inhibition/disinhibition dimensions from established structural models, predicted symptoms of multiple Diagnostic and Statistical Manual of Mental Disorders (4th edition) clinical disorders in 471 community adults. Robust relationships with internalizing disorder symptoms were evident for both trait variables, with THT+ more predictive of fear disorder symptoms and INH- more predictive of distress disorder symptoms. For substance-related problems, prediction was evident only for INH-. Additionally, interactive effects of THT+ and INH- were found for distress disorders, and to a lesser extent, fear disorders. Given their well-established physiological correlates, these dispositional variables represent prime targets for combined psychometric-neurophysiological assessment of broad liabilities to multiple forms of psychopathology.

Impact of childhood adversities on specific symptom dimensions in first-episode psychosis

BACKGROUND

The relationship between childhood adversity (CA) and psychotic disorder is well documented. As the adequacy of the current categorical diagnosis of psychosis is being increasingly questioned, we explored independent associations between different types of CA and specific psychotic symptom dimensions in a well-characterized sample of first-episode psychosis (FEP) patients.

METHOD

This study involved 236 FEP cases aged 18-65 years who presented for the first time to psychiatric services in South London, UK. Psychopathology was assessed with the Positive and Negative Syndrome Scale and confirmatory factor analysis was used to evaluate the statistical fit of the Wallwork/Fortgang five-factor model of psychosis. CA prior to 17 years of age (physical abuse, sexual abuse, parental separation, parental death, and being taken into care) was retrospectively assessed using the Childhood Experience of Care and Abuse Questionnaire.

RESULTS

Childhood sexual abuse [β = 0.96, 95% confidence interval (CI) 0.40-1.52], childhood physical abuse (β = 0.48, 95% CI 0.03-0.93) and parental separation (β = 0.60, 95% CI 0.10-1.11) showed significant associations with the positive dimension; while being taken into care was associated with the excited dimension (β = 0.36, 95% CI 0.08-0.65), independent of the other types of CA. No significant associations were found between parental death and any of the symptom dimensions.

CONCLUSIONS

A degree of specificity was found in the relationships between different types of CA and psychosis symptom dimensions in adulthood, suggesting that distinct pathways may be involved in the CA-psychosis association. These potentially different routes to developing psychosis merit further empirical and theoretical exploration.

A new approach to eating-disorder classification: Using empirical methods to delineate diagnostic dimensions and inform care

OBJECTIVE

Despite changes to the diagnostic criteria for eating disorders (EDs) in the DSM-5, the current diagnostic system for EDs has limited ability to inform treatment planning and predict outcomes. Our objective was to test the clinical utility of a novel dimensional approach to understanding the structure of ED psychopathology.

METHOD

Participants (N = 243; 82.2% women) were community-recruited adults with a DSM-5 ED assessed at baseline, 6-month, and 1-year follow-up. Hierarchical factor analysis was used to identify a joint hierarchical-dimensional structure of eating, mood, and anxiety symptoms. Exploratory structural equation modeling was used to test the ability of the dimensional model to predict outcomes.

RESULTS

At the top of the hierarchy, we identified a broad Internalizing factor that reflected diffuse symptoms of eating, mood, and anxiety disorders. Internalizing branched into three subfactors: distress, fear-avoidance (fears of certain stimuli and behaviors to neutralize fears, including ED behaviors designed to reduce fear of weight gain), and body dissatisfaction, which was nested within distress. The lowest level of the hierarchy was characterized by 15 factors. The hierarchical model predicted 60.1% of the variance in outcomes at 6-month follow-up, whereas all DSM eating, mood, and anxiety disorders combined predicted 35.8% of the variance in outcomes.

DISCUSSION

A dimensional approach to understanding and diagnosing EDs improved the ability to prospectively predict clinical course above-and-beyond the traditional categorical (DSM-based) approach. Our findings have implications for endeavors to improve the prediction of ED prognosis and course, and to develop more effective trans-diagnostic treatments.

Foundations of oral health-related quality of life

Oral health-related quality of life (OHRQOL) is the component of health-related quality of life that relates to the effects of oral diseases and dental interventions on patients. This article describes why OHRQOL is important and how it is measured. The conceptual basis for OHRQOL is discussed. A four-dimensional structure consisting of Oral Function, Orofacial Pain, Orofacial Appearance and Psychosocial Impact as the OHRQOL dimensions has emerged as psychometrically sound and clinically intuitive. Consequently, when the impact of oral diseases or the effects of dental interventions are measured, four dimension scores capturing these attributes need to be used.

Neuroanatomical profiles of alexithymia dimensions and subtypes

Alexithymia, a major risk factor for a range of psychiatric and neurological disorders, has been recognized to comprise two dimensions, a cognitive dimension (difficulties identifying, analyzing, and verbalizing feelings) and an affective one (difficulties emotionalizing and fantasizing). Based on these dimensions, the existence of four distinct alexithymia subtypes has been proposed, but never empirically tested. In this study, 125 participants were assigned to four groups corresponding to the proposed alexithymia subtypes: Type I (impairment on both dimensions), Type II (impairment on the cognitive, but not the affective dimension), Type III (impairment on the affective, but not the cognitive dimension), and Lexithymics (no impairment on either dimension). By means of voxel-based morphometry, associations of the alexithymia dimensions and subtypes with gray and white matter volumes were analyzed. Type I and Type II alexithymia were characterized by gray matter volume reductions in the left amygdala and the thalamus. The cognitive dimension was further linked to volume reductions in the right amygdala, left posterior insula, precuneus, caudate, hippocampus, and parahippocampus. Type III alexithymia was marked by volume reduction in the MCC only, and the affective dimension was further characterized by larger sgACC volume. Moreover, individuals with the intermediate alexithymia Types II and III showed gray matter volume reductions in distinct regions, and had larger corpus callosum volumes compared to Lexithymics. These results substantiate the notion of a differential impact of the cognitive and affective alexithymia dimensions on brain morphology and provide evidence for separable neuroanatomical representations of the different alexithymia subtypes.

Do symptom dimensions or categorical diagnoses best discriminate between known risk factors for psychosis?

OBJECTIVE

To describe symptom dimensions of psychosis using detailed psychopathological information from epidemiologically defined incident cases which include the full spectrum of functional psychosis across all age ranges. Then, assess the comparative usefulness of the dimensional and categorical representations of psychosis in discriminating between demographic and pre-morbid risk factors.

METHOD

A total of 464 incident cases of psychosis assessed with OPCRIT (Operational Checklist for Psychotic Symptoms) were included in an exploratory factor analysis. Using Regression analyses we modelled the associations of the dimensional and categorical representations of psychosis with antecedent validating variables and compared the subsequent models using the likelihood ratio test.

RESULTS

Factor analysis produced five-symptom dimensions, manic, disorganisation, depressive, delusional and auditory hallucinatory symptoms, explaining 58% of the total variance. Different dimensions were differentially associated with the pre-morbid risk factors. Neither the dimensional nor the categorical representations on their own were sufficient to explain associations with the antecedent validating variables.

CONCLUSION

Neither the dimensional or the diagnostic representation of psychosis was superior in discriminating between known risk factors, combining dimensional measures with categorical diagnoses will probably be more informative in determining the causes and correlates of psychosis.

Morphometric analysis of the YESS and TESSYS techniques of percutaneous transforaminal endoscopic lumbar discectomy

Posterior lateral endoscopic nucleotomy is widely accepted as a minimally invasive surgery for lumbar disc herniation, but few studies have compared the transforaminal approach using two different techniques, YESS and TESSYS. One hundred and fifty lumbar IVFs of cadaveric spines were studied. Eighteen-gauge needles were inserted percutaneously toward IVFs into the discs by either YESS or TESSYS. The distances from the needle to the nerve root and from the needle to the spinal dura were measured and compared across different spinal segments. The incidence of nerve roots compression by the operating endoscope was measured. The mean distances from needle to the nerve root and spinal dura in YESS were 3.5 ± 1.4 mm and 6.6 ± 1.9 mm. The respective mean distances in TESSYS were 4.6 ± 1.5 mm and 5.9 ± 1.4 mm. The distance from needle to the nerve root was longer in TESSYS, while the distance from the needle to spinal dura was longer in YESS. The distance from needle to nerve was shorter in proximal segments. The incidence of operating endoscope compression of the nerve root was high in both of techniques. The difference in theory and design between YESS and TESSYS, "intradisc" versus "intracanal", was confirmed by comparison of anatomic distances from the needle to the nerve. Puncture of the annulus in the distal lumbar is safer than proximal puncture. The high incidence of endoscope compression of the nerve root may be related with the transient postoperative dysaesthesia.

Neural encoding of large-scale three-dimensional space-properties and constraints

How the brain represents represent large-scale, navigable space has been the topic of intensive investigation for several decades, resulting in the discovery that neurons in a complex network of cortical and subcortical brain regions co-operatively encode distance, direction, place, movement etc. using a variety of different sensory inputs. However, such studies have mainly been conducted in simple laboratory settings in which animals explore small, two-dimensional (i.e., flat) arenas. The real world, by contrast, is complex and three dimensional with hills, valleys, tunnels, branches, and—for species that can swim or fly—large volumetric spaces. Adding an additional dimension to space adds coding challenges, a primary reason for which is that several basic geometric properties are different in three dimensions. This article will explore the consequences of these challenges for the establishment of a functional three-dimensional metric map of space, one of which is that the brains of some species might have evolved to reduce the dimensionality of the representational space and thus sidestep some of these problems.