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International audience; IntroductionIn clinical practice, the usefulness of diagnosis based on the Diagnostic or Statistical Manual of Mental Disorders (DSM) or the International Classification of Diseases, 11th edition, appears essential from a clinical, research, epidemiological, administrative, economic and political level. However, such diagnostic systems have shortcomings in terms of validity, little consideration of comorbidities and strong intra-class heterogeneity. On a structural level, the operationalization of its criteria is based on a reliability which has been defined a posteriori and which does not lead to improving the validity of the diagnosis but rather to the reification of the diagnostic categories.MethodsFirst published in its current form in 2017, the Hierarchical Taxonomy of Psychopathology (HiTOP) constitutes a nosological alternative based on statistics. It conceptualizes psychopathology as a set of hierarchical dimensions, i.e. in “transdiagnostic” continua. The HiTOP is structured according to super-spectra, spectra, sub-factors, syndromes, components and symptoms. This comes from the current dimensional psychology and quantitative nosology. This article describes the basic principles of the HiTOP project and its potential to integrate into clinical and psychiatric research based on its advantages and limitations.ResultsUnlike the DSM, which is descriptive and categorical, the HiTOP is first a dimensional classification. This dimensionality describes psychiatric phenomena on continua, each dimension providing a diagnostic continuum to situate a clinical patient. This dimensionality avoids the reification of categories and it limits the dichotomy between normal and pathological. In addition, HiTOP shows a hierarchical structure: vertical refinement of dimensions allows to circumvent the problem of comorbidities, proposes a new conception of etiopathogenic mechanisms, and improves management of care.DiscussionThus, we provide an illustration of the applications of a dimensional and hierarchical classification in current clinical practice and scientific research, compared to traditional nosology. The challenges of the HiTOP arise in terms of validity, i.e. in the relation of dimensions with physiopathological mechanisms, in clinical terms, i.e. in the potential contribution of dimensions in relation to categories. Moreover, methodological challenges will be important given the inherent limitations of the HiTOP.ConclusionThe HiTOP allows to examine the conceptualization of psychiatric disorders, the search for explanatory mechanisms, and treatment from another perspective for psychiatry.; IntroductionLes diagnostics fondés sur des classifications comme le Manuel Diagnostique ou Statistique des troubles mentaux (DSM) ou la Classification Internationale des Maladies, 11e édition représente une pierre angulaire de la pratique clinique. Leur utilité paraît essentielle d’un point de vue clinique, de la recherche, de l’épidémiologie, ainsi qu’au niveau administratif, économique et politique. Cependant, de tels systèmes diagnostiques présentent des lacunes en termes de validité, une prise en considération des comorbidités peu pertinente et une forte hétérogénéité intraclasse.MéthodesLa taxonomie hiérarchique de la psychopathologie (HiTOP), publiée en 2017 sous sa forme actuelle, constitue une alternative fondée sur les statistiques. Elle conceptualise la psychopathologie comme un ensemble de dimensions organisées de manière hiérarchique, c’est-à-dire en continua « transdiagnostiques » de plus en plus larges. Cet article décrit les principes de base du projet de la HiTOP et son potentiel à s’intégrer dans la clinique et la recherche psychiatrique en fonction de ses avantages et de ses limites.RésultatsLa HiTOP est une classification dimensionnelle (et non catégorielle, comme la classification DSM) et elle possède une structure hiérarchique. Nous fournissons ainsi une illustration des applications d’une approche dimensionnelle et hiérarchique, par rapport à la nosologie traditionnelle, en discutant les obstacles à son utilisation dans l’environnement réel de la clinique et de la recherche. Nous détaillons également ses rapports à la thérapeutique et à la compréhension mécanistique neurobiologique des troubles psychiatriques.ConclusionLa HiTOP permet d’examiner sous une autre perspective la conceptualisation des troubles psychiatriques, la recherche des mécanismes explicatifs et les prises en charge.

Attention deficit with or without hyperactivity disorder (ADHD) is one of the most frequent neuropsychiatric disorders, and affects 2-4% of adults. In contrast with many European countries, the identification and management of adult ADHD remains underdeveloped in France, and a subject of controversy. This review provides a practical update on current knowledge about ADHD in adults for French-speaking professionals who have to detect or manage adult patients with ADHD. ADHD is classified as a neurodevelopmental disorder in the recent update of the international diagnostic classification. While symptoms and impairment due to ADHD are frequently severe during childhood, they often evolve as children grow older, with frequent persistent disabilities in adulthood. In adulthood, the clinical presentation, as in childhood, involves the symptom triad of inattention, hyperactivity and impulsivity. However, differences are noted: hyperactivity is more often internalized, symptoms of inattention may be masked by anxiety symptoms or obsessive-like compensation strategies. ADHD is often diagnosed during childhood, but it is not rare for the diagnosis to be made later. Failure to recognise symptoms resulting in misdiagnosis, or alternatively well-developed compensation factors could be two underlying reasons for the long delay until diagnosis. Other symptoms, such as emotional deregulation or executive function-related symptoms are also usually observed in adults. In addition, in adults, ADHD is often associated with other psychiatric disorders (in 80% of cases); this makes the diagnosis even more difficult. These disorders encompass a broad spectrum, from mood disorders (unipolar or bipolar), to anxiety disorders, and other neurodevelopmental disorders and personality disorders, especially borderline and antisocial personality disorder. Substance-use disorders are very common, either as a consequence of impulsivity and emotional dysregulation or as an attempt at self-treatment. Sleep disorders, especially restless leg syndrome and hypersomnolence, could share common pathophysiological mechanisms with ADHD. ADHD and comorbidity-related symptoms are responsible for serious functional impairment, in various domains, leading to academic, social, vocational, and familial consequences. The impact on other psychiatric disorders as an aggravating factor should also be considered. The considerable disability and the poorer quality of life among adults with ADHD warrant optimal evaluation and management. The diagnostic procedure for ADHD among adults should be systematic. Once the positive diagnosis is made, the evaluation enables characterisation of the levels of severity and impairment at individual level. A full examination should also assess medical conditions associated with ADHD, to provide personalized care. In recent years, a growing number of assessment tools have been translated and validated in French providing a wide range of structured interviews and standardized self-report questionnaires for the evaluation of core and associated ADHD symptoms, comorbidities and functional impairment. The treatment of ADHD in adults is multimodal, and aims to relieve the symptoms, limit the burden of the disease, and manage comorbidities. The most relevant and validated psychological approaches are psycho-education, cognitive-behavioural therapy and "third wave therapies" with a specific focus on emotional regulation. Cognitive remediation and neurofeedback are promising strategies still under evaluation. Medications, especially psychostimulants, are effective for alleviating ADHD symptoms with a large effect size. Their safety and tolerance are satisfactory, although their long-term clinical benefit is still under discussion. In France, methylphenidate is the only stimulant available for the treatment of ADHD. Unfortunately, there is no authorization for its use among adults except in continuation after adolescence. Hence the prescription, which is subject to the regulations on narcotics, is off-label in France. This article aims to provide practical considerations for the management of ADHD and associated disorders in adults, in this particular French context.