Preface

Attention Deficit Hyperactivity Disorder (ADHD) is not only the most prevalent neurodevelopmental disorder but also a very contradictory one. This book provides a comprehensive overview of ADHD, with a focus on diagnosis and comorbidity.

The Introductory Chapter, "ADHD Has Many Faces" by Prof. Hojka Gregoric Kumperscak, presents ADHD as a disorder with a vivid history of changing names, diagnostic criteria, and clinical point of view. Previously, it was considered a disorder that affected children only. Recently, however, there is no doubt that ADHD can affect adults as well, but with different clinical presentation. Thus, it is critical to understand how the clinical picture of the disorder changes with development.

Chapter 2, "Traditional Scales Diagnosis and Endophenotypes in Attentional Deficits Disorders: Are We on the Right Track?" by Annabel Jiménez-Soto, Juan Pedro Vargas, Estrella Díaz and Juan Carlos López, discusses the necessity of broadening diagnostic thinking away from the boundaries of traditional assessment (based on questionnaires and behavioural scales). One way to do this is to study the vulnerable traits associated with impulsivity and attentional deficit. In a quantitative fashion, these traits could be used to define a specific endophenotype. This view would allow a more precise medical/psychological assessment of the patient along the life span, avoiding a diagnosis based on the number of symptoms only.

When working with parents it is important to determine whether there is a genetic basis for ADHD. New genetic studies bring deeper and more concise knowledge about the disorder's aetiology. As discussed in Chapter 3, "Role of Copy Number Variations in ADHD" by Danijela Krgović, copy number variations (CNVs) have an important role in the aetiology of neurodevelopmental disorders (NDDs), including ADHD. CNVs provide new opportunities for studying and managing psychiatric disorders in general. Identification of disease-associated genes and knowledge of their molecular functions will lead to a better understanding of their disease pathology and hopefully enable better diagnosis and treatment. Genetic counselling for polygenic disorders with complex genetic architecture like ADHD is challenging due to variable phenotypic outcomes and incomplete penetrance encountered in most genetic disorders. Therefore, understanding molecular aetiology is useful for patient management in terms of improving risk predictions, screening for extrapsychiatric features, and tailoring treatment to the individual.

Comorbidity is a rule, especially if ADHD is not recognised and treated early. As discussed in Chapter 4, "Comorbidity in Children and Adolescents with ADHD" the presence of comorbidities largely depends on case definition, assessment methodology, and control group. Studies show that 67%–80% of children diagnosed with ADHD have at least one other diagnosis, and almost half of them have two. Two-thirds of children with ADHD have at least one other psychiatric disorder. Specific learning difficulties are more common in people with ADHD than in the general population with a prevalence of 45%. The most common learning difficulties in children with ADHD are in the areas of reading, spelling, writing, and math.

Children with ADHD have greater learning difficulties than children who have only specific learning difficulties.

It is crucial to be aware of comorbidities because they complicate the diagnostic and therapeutic processes as well as affect the course and prognosis of the disorder. Assessment and support in comorbid disorders are often as important as the assessment and treatment of ADHD symptoms.

Chapter 5, "ADHD and Impact on Language" by Clay Brites, discusses language abnormalities as some of the most common ADHD comorbidities. The language problem in ADHD can be expressed at any age and at different intensity levels. These abnormalities can negatively affect daily activities and the learning process, which depends on proper language acquisition during the child's development. The abnormalities in language result in greater unsatisfactory evolution and many problems in verbal and non-verbal abilities, adversely impacting academic life because of losses in reading and writing appropriation. Thus, it is essential to understand the facts that interrelate ADHD with the cognitive and language development process and where and how ADHD neurobiological dysfunctions affect the dynamic of the neural network responsible for receptive, integrative, and expressive language structure at different child neurodevelopment levels.

Chapter 6, "Adult Attention-Deficit/Hyperactivity Disorder and Substance Use Disorder: A Systematic Review of the Literature" by Anja Plemenitaš Ilješ, discusses untreated ADHD and how it is highly comorbid with substance use disorder (SUD). ADHD is diagnosed in up to 20% of patients with SUD. The two disorders are believed to have shared pathophysiology. ADHD is associated with most dependence diagnoses. Evidence on pharmacological treatment is limited, but new trials support the use of a higher dose of long-acting stimulants combined with psychotherapy. The decision to treat adult ADHD in the context of SUD depends on various factors, so clinical decisions should be individualized and based on a careful analysis of the advantages and disadvantages of pharmacological treatment for ADHD in the context of SUD.

This book addresses all these issues to bring more clarity and understanding of ADHD to clinicians, scientists, researchers, and family members of those with the disorder.

> **Hojka Gregorič Kumperščak** Department of Paediatrics and University of Maribor, Faculty of Medicine, University Medical Centre Maribor, Maribor, Slovenia

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