Le trouble du déficit de l’attention avec hyperactivité (TDAH) est un trouble neurodéveloppemental (TND) comme le trouble du spectre par de l’autistisme, les troubles spécifiques de l’apprentissage, le trouble de la coordination du développement et le syndrome de Gilles de la Tourette. Les TND peuvent être comorbides entre eux et avec d’autres affections psychiatriques ou non psychiatriques, rendant parfois le diagnostic du trouble index assez difficile selon l’âge et le sexe du patient. Le TDAH touche raisonnablement 2 % des enfants d’âge préscolaire, 4 % des enfants d’âge scolaire, 3 % des adultes et 1 % des personnes de plus de 60 ans. Plus de deux millions de personnes sont probablement concernées en France. Les critères de diagnostic sont strictement cliniques et sont fixés depuis plus de vingt ans dans des classifications internationales telles que le Manuel diagnostique et statistique de l’American Psychiatric Association et la Classification internationale des maladies de l’Organisation mondiale de la santé. Il n’existe pas de biomarqueur fiable permettant de poser ou d’écarter le diagnostic. Les conséquences d’un retard ou d’une absence de diagnostic peuvent être dramatiques pour les enfants et leurs familles. Dans cet article, nous abordons la démarche de dépistage et de diagnostic du TDAH : identification des symptômes cardinaux et de leurs répercussions, identification des diagnostics différentiels et des diagnostics comorbides, examens complémentaires à prescrire éventuellement. Ces éléments seront utiles pour déterminer la stratégie thérapeutique, le suivi du patient et la surveillance d’un éventuel traitement médicamenteux. Nous proposons une liste d’échelles d’évaluation et d’entretiens semi-standardisés, parmi lesquels le clinicien pourra choisir d’utiliser le plus approprié en fonction de l’objectif poursuivi : dépistage, diagnostic du TDAH et évaluation de ses conséquences, ou évaluation psychopathologique plus large. En conclusion, le diagnostic de TDAH ne repose sur aucun test biologique, électrophysiologique ou neuropsychologique, ni sur l’imagerie cérébrale. Il doit être posé par un médecin formé au développement normal de l’enfant et aux troubles neurodéveloppementaux, selon une démarche raisonnée.

Attention Deficit Hyperactivity Disorder (ADHD) is classified within the family of neurodevelopmental disorders (NDDs), sharing the category with conditions such as Autism Spectrum Disorder, Specific Learning Disorders, Developmental Coordination Disorder, and Gilles de la Tourette Syndrome, among others. NDDs often coexist with one another and with various psychiatric or non-psychiatric conditions, which can obscure the primary disorder's diagnosis, especially when considering the patient's age and gender. Psychiatric comorbidities encompass both internalizing disorders, such as anxiety and depression, and externalizing disorders, including oppositional defiant disorder and conduct disorder. While daydreaming and emotional dysregulation are frequently observed in children and adults with ADHD, they do not constitute diagnostic criteria for the disorder but rather comorbid features. The concomitant presence of these disorders can create complex clinical pictures, necessitating nuanced and careful management strategies. Comorbidities extending beyond psychiatric realms include various sleep disorders (disruptions in circadian rhythms, bruxism, enuresis, restless legs syndrome, among others), neurological conditions such as epilepsy and migraine, as well as atopic conditions, inflammatory and autoimmune diseases, and certain genetic syndromes, but not only. In children younger than six years old – recognizing that ADHD can be considered for diagnosis at this early stage – the manifestations of various disorders frequently intertwine, culminating in an overarching phenotype. As children age, these symptom clusters tend to become more distinct and individualized. In contrast to males, females diagnosed with ADHD are less likely to exhibit conspicuous signs of hyperactivity and impulsivity. They might adopt compensatory behaviors to obscure or diminish the manifestation of their symptoms. Furthermore, females have an increased likelihood of developing comorbid internalizing disorders, such as anxiety and depression, as opposed to externalizing disorders, which may contribute to the underdiagnosis of ADHD in this population. The prevalence of ADHD is non-negligible, affecting an estimated 2% of pre-schoolers, 4% of school-aged children, 3% of adults, and 1% of the population aged over 60, implicating more than two million individuals in France alone. Diagnostic criteria are exclusively clinical and have remained unchanged for over two decades in international classifications such as the Diagnostic and Statistical Manual of the American Psychiatric Association and the International Classification of Diseases by the World Health Organization. The absence of a reliable biomarker to confirm or refute the diagnosis underscores the challenges in ADHD identification. The ramifications of diagnostic delay or oversight are profound, potentially leading to dire consequences for affected children and their families, including elevated risks of suicidal behavior in adolescents and adults and increased potential for legal entanglements, even incarceration. This review article delineates the systematic approach to ADHD screening and diagnosis, including the identification of hallmark symptoms and their impacts, differentiation from other diagnoses, and the contemplation of ancillary assessments that may be warranted. These components are pivotal for informing therapeutic strategies, patient management, and the oversight of pharmacological interventions and their adverse effects. We furnish a compendium of evaluative scales and semi-structured interviews for clinical utility, enabling practitioners to elect tools best suited to their expertise and the diagnostic or evaluative objectives at hand. In sum, the diagnosis of ADHD is predicated on a methodical clinical assessment executed by a practitioner well versed in typical child development and neurodevelopmental disorders, eschewing reliance on supplemental biological, electrophysiological, neuropsychological testing, or neuroimaging.