This groundbreaking volume, published by the American Psychological Association in partnership with the International Union of Psychological Science, provides a detailed guide to clinical diagnosis by psychologists and other health professionals based on the eleventh revision of the World Health Organization's International Classification of Diseases (ICD- ). The ICD- was adopted by the World Health Assembly in 2 9 and came into effect as the global standard for health information and reporting in 2 22. The ICD is the diagnostic system for mental disorders most widely used by mental health professionals around the world in their day-to-day clinical practice. This edited volume offers a step-by-step approach to diagnosis, giving mental health professionals around the world the tools they need to apply ICD- diagnostic requirements for mental, behavioral, and neurodevelopmental disorders as the basis for delivering high quality, evidence-informed care. A psychological approach to diagnosis is a conceptually driven, person-oriented, biopsychosociocultural formulation that integrates pertinent history, behavior, symptoms, phenomenology, and functioning.  A psychological approach focuses on psychological mechanisms and principles as an aspect of diagnostic practice and case formulation, regardless of professional discipline.   The chapters of this book cover the major groupings of mental disorder as well as related areas that are important parts of psychological practice, such as sexual dysfunctions, sleep-wake disorders, and relationship problems and maltreatment. The authors of this book are leading global experts in each area, many of whom were integrally involved in developing the respective sections of the ICD- .   Authors describe the overarching logic for the classificatory arrangement and the elements of a psychological approach to the set of disorders discussed in each chapter, including psychological models for conceptualizing their symptoms and recommendations for psychological assessment. The chapters also discuss presentations and symptom patterns for each major group of disorders, specifiers and subtypes, the threshold between normal variation and disorder, differential diagnoses, co-occurring disorders, developmental course, cultural and contextual considerations, and gender-related features.  A Psychological Approach to Diagnosis is the first comprehensive training resource on WHO amp rsquo s ICD- classification of mental, behavioural and neurodevelopmental disorders. It provides practicing psychologists and other mental health professionals, primary care clinicians, educators, and trainees with essential tools for the competent practice of diagnosis using the ICD- as a framework.