Reconsidering the classification of schizophrenia and manic depressive illness--a critical analysis and new conceptual model

Testing the expanded continuum hypothesis of schizophrenia and bipolar disorder. Neural and psychological evidence for shared and distinct mechanisms

Despite the traditional view of Schizophrenia (SZ) and Bipolar disorder (BD) as separate diagnostic categories, the validity of such a categorical approach is challenging. In recent years, the hypothesis of a continuum between Schizophrenia (SZ) and Bipolar disorder (BD), postulating a common pathophysiologic mechanism, has been proposed. Although appealing, this unifying hypothesis may be too simplistic when looking at cognitive and affective differences these patients display. In this paper, we aim to test an expanded version of the continuum hypothesis according to which the continuum extends over three clusters: the psychotic, the cognitive, and the affective. We applied an innovative approach known as Source-based Morphometry (SBM) to the structural images of 46 individuals diagnosed with SZ, 46 with BD and 66 healthy controls (HC). We also analyzed the psychological profiles of the three groups using cognitive, affective, and clinical tests. At a neural level, we found evidence for a shared psychotic core in a distributed network involving portions of the medial parietal and temporo-occipital areas, as well as parts of the cerebellum and the middle frontal gyrus. We also found evidence of a cognitive core more compromised in SZ, including alterations in a fronto-parietal circuit, and mild evidence of an affective core more compromised in BD, including portions of the temporal and occipital lobes, cerebellum, and frontal gyrus. Such differences were confirmed by the psychological profiles, with SZ patients more impaired in cognitive tests, while BD in affective ones. On the bases of these results we put forward an expanded view of the continuum hypothesis, according to which a common psychotic core exists between SZ and BD patients complemented by two separate cognitive and affective cores that are both impaired in the two patients' groups, although to different degrees.

Lamotrigine as a mood stabilizer: insights from the pre-clinical evidence

INTRODUCTION

Lamotrigine (LTG) is a well-established anticonvulsant that is also approved for the prevention of mood relapses in bipolar disorder. However, the mechanisms underlying LTG mood stabilizing effects remain unclear. Areas covered: Herein, the pre-clinical evidence concerning LTG's' mode of action in depression and mania is reviewed. Bottlenecks and future perspectives for this expanding and promising field are also discussed. Pre-clinical studies have indicated that neurotransmitter systems, especially serotoninergic, noradrenergic and glutamatergic, as well as non-neurotransmitter pathways such as inflammation and oxidative processes might play a role in LTG's antidepressant effects. The mechanisms underlying LTG's anti-manic properties remain to be fully explored, but the available pre-clinical evidence points out to the role of glutamatergic neurotransmission, possibly through AMPA-receptors. Expert opinion: A major limitation of current pre-clinical investigations is that there are no experimental models that recapitulate the complexity of bipolar disorder. Significant methodological differences concerning time and dose of LTG treatment, administration route, animal strains, and behavioral paradigms also hamper the reproducibility of the findings, leading to contradictory conclusions. Moreover, the role of other mechanisms (e.g. inositol phosphate and GSK3β pathways) implicated in the mode of action of different mood-stabilizers must also be consolidated with LTG.

The slow death of the concept of schizophrenia and the painful birth of the psychosis spectrum

The concept of schizophrenia only covers the 30% poor outcome fraction of a much broader multidimensional psychotic syndrome, yet paradoxically has become the dominant prism through which everything 'psychotic' is observed, even affective states with mild psychosis labelled 'ultra-high risk' (for schizophrenia). The inability of psychiatry to frame psychosis as multidimensional syndromal variation of largely unpredictable course and outcome - within and between individuals - hampers research and recovery-oriented practice. 'Psychosis' remains firmly associated with 'schizophrenia', as evidenced by a vigorous stream of high-impact but non-replicable attempts to 'reverse-engineer' the hypothesized biological disease entity, using case-control paradigms that cannot distinguish between risk for illness onset and risk for poor outcome. In this paper, the main issues surrounding the concept of schizophrenia are described. We tentatively conclude that with the advent of broad spectrum phenotypes covering autism and addiction in DSM5, the prospect for introducing a psychosis spectrum disorder - and modernizing psychiatry - appears to be within reach.

NMDA receptor and schizophrenia: a brief history

Although glutamate was first hypothesized to be involved in the pathophysiology of schizophrenia in the 1980s, it was the demonstration that N-methyl-D-aspartate (NMDA) receptor antagonists, the dissociative anesthetics, could replicate the full range of psychotic, negative, cognitive, and physiologic features of schizophrenia in normal subjects that placed the "NMDA receptor hypofunction hypothesis" on firm footing. Additional support came from the demonstration that a variety of agents that enhanced NMDA receptor function at the glycine modulatory site significantly reduced negative symptoms and variably improved cognition in patients with schizophrenia receiving antipsychotic drugs. Finally, persistent blockade of NMDA receptors recreates in experimental animals the critical pathologic features of schizophrenia including downregulation of parvalbumin-positive cortical GABAergic neurons, pyramidal neuron dendritic dysgenesis, and reduced spine density.

The forthcoming revision of the diagnostic and classificatory system: perspectives based on the European psychiatric tradition

Europe has a rich tradition in psychopathology and psychiatric classification. This could be helpful developing new classification systems like ICD-11 and DSM-V. Some examples of this are described and further discussed, such as the categorical vs. the syndromatological approach, the relevance of hierarchical rules for the delineation of nosological entities, the antagonistic tradition of unitarian vs. splitting approaches and the relevance of a differentiated psychopathological description. Finally, the conclusion is that a too radical change of the classificatory system, e.g. in the direction of a purely symptomatical/dimensional systematic, or a totally new classification based on modern new biological findings, might be problematic and premature.

Systematic of psychiatric disorders between categorical and dimensional approaches: Kraepelin's dichotomy and beyond

This paper describes basic principles of systematics for psychiatric disorders such as the categorical and dimensional approach. It summarises validity aspects of the traditional psychiatric nosology and syndromatology. The importance and limitations of the dichotomy of schizophrenia and affective disorders, first suggested by Kraepelin, is reviewed in the light of results from modern research in the field of classification, follow-up and neurobiological studies, especially neurochemical, neurogenetic and neuroimaging studies. Current developments towards DSM-V and ICD-11 are critically reflected. The conclusion is reached that there might be insufficient data to establish a new systematics of psychoses. Therefore it might be premature to leave the Kraepelinian dichotomy totally although it has to be modified in the light of new research.

Is brain banking of psychiatric cases valuable for neurobiological research?

It is widely accepted that neurobiological abnormalities underlie the symptoms of psychiatric disorders such as schizophrenia and unipolar or bipolar affective disorders. New molecular methods, computer-assisted quantification techniques and neurobiological investigation methods that can be applied to the human brain are all used in post-mortem investigations of psychiatric disorders. The following article describes modern quantitative methods and recent post-mortem findings in schizophrenia and affective disorders. Using our brain bank as an example, necessary considerations of modern brain banking are addressed such as ethical considerations, clinical work-up, preparation techniques and the organization of a brain bank, the value of modern brain banking for investigations of psychiatric disorders is summarized.

'Mental retardation' or 'intellectual disability': time for a conceptual change

BACKGROUND

The term 'mental retardation' (MR) is outdated and has changed to 'intellectual disability' (ID). Unfortunately, this decision did not follow a nosology approach. The aim of this overview is twofold: (1) to provide a conceptual background and framing on the ID/MR field to other psychiatrists, and (2) to provide a nosology-based perspective to the debate on the name and concept of MR/ID.

METHOD

This conceptual paper is based on a literature review and on an iterative process of debate within the WPA Section 'Psychiatry of Mental Retardation'.

RESULTS

ID may be regarded not as a disease or as a disability but as a syndrome grouping (metasyndrome) similar to the construct of dementia. It includes a heterogeneous group of clinical conditions, ranging from genetic to nutritional, infectious, metabolic or neurotoxic conditions. The ID metasyndrome is characterized by a deficit in cognitive functioning prior to the acquisition of skills through learning. The intensity of the deficit is such to interfere in a significant way with individual normal functioning as expressed in limitations in activities and restriction in participation (disabilities).

CONCLUSIONS

The name 'developmental cognitive impairment' is here suggested to coexist with ID for naming the metasyndrome previously called MR following a polysemic-polynomious approach.

Classification in psychiatry: Does it deliver in schizophrenia and depression?

Background

In the context of ongoing work to develop the next iteration of psychiatric classification systems, we briefly review the performance of current systems against their own stated objectives, for two major diagnostic groupings.

Discussion

In the major groupings of schizophrenia and depression, experience over the last 50 years has highlighted particular inadequacies in the utility and validity of available classifications.

Summary

Advances in psychiatric knowledge and practice notwithstanding, present classification systems would be enhanced by the incorporation of dimensional components. Minor tinkering with current systems will reflect only a missed opportunity. Improving classification will facilitate quality improvement of mental health systems.

Towards a possible aetiology for depressions?

BACKGROUND

Since a genetic disposition for depression is probable, there ought to be biochemical changes. Increased peptide levels with relevant bioactivities have been found in urine in a previous investigation, which may be such changes.

METHODS

Urine from patients with severe depression according to ICD 10 have been run on reversed phase High Performance Liquid Chromatography, and off line mass spectrometry was performed on some of these peptides.

RESULTS

We find overlapping patterns of peptide peaks in severe depression, but with considerable individuality. Mass spectrometry shows that some of these peptides are probably of dietary origin, because their sequences are found only in certain dietary proteins. Opioids from casein and gliadin are typical examples.

CONCLUSION

Our data show that the disposition must be polygenetic because some peptide peaks with the same bioactivity are of different length in different patients, but with the same diagnosis. However, some of the peaks are common Peptide increase in urine is found when break down is deficient, and the data presented agree with reports on peptidase deficiencies in depression. Antidepressant drugs decrease the peptide level after about 3 weeks.

Deconstructing bipolar disorder: a critical review of its diagnostic validity and a proposal for DSM-V and ICD-11

The development of Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, and International Classification of Diseases, Eleventh Edition, deserves a significant conceptual step forward. There is a clear need to improve and refine the current diagnostic criteria, but also to introduce dimensions, perhaps not as an alternative but rather as a useful complement to categorical diagnosis. Laboratory, family, and treatment response data should also be systematically included in the diagnostic assessment when available. We have critically reviewed the content, concurrent, discriminant, and predictive validity of bipolar disorder, and to overcome the validity problems of the current classifications of mental disorders, we propose a modular system which may integrate categorical and dimensional issues, laboratory data, associated nonpsychiatric medical conditions, psychological assessment, and social issues in a comprehensive and nevertheless practical approach.

Social and symptomatic outcomes of first-episode bipolar psychoses in an early intervention service

AIM

We aimed to establish the relative proportions of all diagnoses in people aged 14-35 years presenting to an early intervention in psychosis service, and to compare demographic variables, symptoms and outcomes between the bipolar psychoses and other psychoses at 3-6 months and 1 year post referral.

METHODS

Prospective 3- to 6-month diagnostic and symptomatic assessments were carried out. Diagnoses were established using the Diagnostic Interview for Psychoses - Diagnostic Module. Symptoms and outcomes were assessed using standardized instruments at 3-6 months and 1 year. Bipolar diagnoses were grouped together in a bipolar group (n=16) and compared with all other diagnoses, in a non-bipolar group (n=62). Parallel analysis was carried out using groups of lifetime elevated, expansive or irritable mood (n=32) and no lifetime elevated, expansive or irritable mood (n=46).

RESULTS

Bipolar disorders account for 20.5% of all new presentations to our service. Differences in outcomes over the range of psychotic diagnoses relate to early presence of negative symptoms. Psychoses with bipolar diagnoses or lifetime elevated, expansive or irritable mood showed lower rates of negative symptoms than other psychoses and had a higher quality of life and higher function at 3-6 months and 1 year.

CONCLUSIONS

Planning for future early intervention services should take the high rate of affective psychoses and their need for diagnosis-specific, evidence-based treatments into account. Lifetime elevated, expansive or irritable mood may predict improved outcomes in early psychoses, possibly mediated by lower levels of negative symptoms.

New Zealand psychiatrists views on global features of ICD-10 and DSM-IV

OBJECTIVE

The present accepted classificatory systems (ICD-10 and DSM-IV) represent the culmination of 100 years of post-Kraepelinian evolution. The present paper reports on a study to ascertain the views of New Zealand psychiatrists on their requirements of a classificatory system, and their opinions on those currently in use.

METHOD

An anonymous postal survey of 542 psychiatrists and trainees was undertaken in New Zealand.

RESULTS

A total of 235 questionnaires were returned, completed. New Zealand psychiatrists primarily use DSM-IV and do so because that is what they were taught on. They make relatively limited use of the multiaxiality. The purposes of classificatory systems that they value most highly are reliable interclinician communication, and to inform patient management planning. The two purposes they valued least were usefulness for a national statistical base, or to indicate prognosis.

CONCLUSIONS

New Zealand psychiatrists' views are consistent with some of the stated objectives of ICD-10 and DSM-IV, but there is significant diversity in the former and over-ambition in the latter, with much to be resolved.

Linkage disequilibrium analyses in the Costa Rican population suggests discrete gene loci for schizophrenia at 8p23.1 and 8q13.3

Linkage studies using multiplex families have repeatedly implicated chromosome 8 as involved in schizophrenia etiology. The reported areas of linkage, however, span a wide chromosomal region. The present study used the founder population of the Central Valley of Costa Rica and phenotyping strategies alternative to DSM-IV classifications in attempts to further delimitate the areas on chromosome 8 that may harbor schizophrenia susceptibility genes. A linkage disequilibrium screen of chromosome 8 was performed using family trios of individuals with a history of psychosis. Four discrete regions showing evidence of association (nominal P values less than 0.05) to the phenotype of schizophrenia were identified: 8p23.1, 8p21.3, 8q13.3 and 8q24.3. The region of 8p23.1 precisely overlaps a region showing strong evidence of linkage disequilibrium for severe bipolar disorder in Costa Rica. The same chromosomal regions were identified when the broader phenotype definition of all individuals with functional psychosis was used for analyses. Stratification of the psychotic sample by history of mania suggests that the 8q13.3 locus may be preferentially associated with non-manic psychosis. These results may be helpful in targeting specific areas to be analyzed in association-based or linkage disequilibrium-based studies, for researchers who have found evidence of linkage to schizophrenia on chromosome 8 within their previous studies.

The effect of gender in diagnosing early schizophrenia--an experimental case simulation study

BACKGROUND

Studies of diagnostic practice confirm that there is a diagnostic delay in diagnosing women with schizophrenia compared to diagnosing men. The aim of the present study was to investigate the diagnostic practice of Norwegian and Russian psychiatrists when it comes to early psychosis, emphasising gender differences. We wanted to study the association between patient gender as such and diagnostic decision-making among psychiatrists.

MATERIALS AND METHODS

Psychiatrists in Norway and the Archangels region in Russia were invited to participate in a study of diagnostic practice, and received a written case description of a patient with early psychosis symptoms that could be interpreted as schizophrenia. They were, however, not informed that 50% of them received a female case description and 50% a male case description. Apart from the patient being described as "he" or "she" the stories were identical. Effects of patient gender, clinician gender, age and main area of interest were estimated using logistic regression analysis.

RESULTS

A total of 467 psychiatrists answered the questionnaire. We found that schizophrenia diagnosis was given significantly more often to the male case than to the female case. Our finding remained significant after adjustment for country, clinician gender, age and main area of interest, and is unlikely to be explained by known biases.

CONCLUSION

Patient gender in itself affects clinicians' diagnostic practice regarding schizophrenia, as schizophrenia diagnosis is given significantly more often to a male case description than to a female one, the descriptions being otherwise identical.

Gene expression microarray studies in polygenic psychiatric disorders: applications and data analysis

Gene expression microarrays have become a mainstream technology that can provide valuable insight into psychiatric disorders. Gene expression studies in post mortem brain samples of schizophrenia and bipolar disorder have the potential to yield novel clues about the pathophysiology of these complex trait disorders. In the present review, a short introduction of the genetic and molecular background of schizophrenia and bipolar disorder is followed by a discussion of the basic concept and limits of gene expression microarray technology, and the complexities surrounding the analysis of thousands of gene transcripts. Although this review is intended for use in most platforms, it has a particular focus on the commercially available Affymetrix system. Various computer programs and their principal features are discussed, and it is shown how these programs can be applied to reveal a biological context of microarray findings. I will demonstrate how the programs can help to judge the results rather than focus on their statistical principles. The strength of gene array experiments is their emphasis on broad, biological themes, rather than on specific genes, and proper biostatistical approaches are important to ensure reproducibility of the findings. All results should be verified by independent means. This review is intended to help brain researchers who want to apply gene expression microarray technology to conceptualize research strategies and sample analysis.