This third edition provides a thorough real-world exploration of the scientist-practitioner model, enabling clinical psychology trainees to develop the core competencies required in an increasingly interdisciplinary healthcare environment. The book has been comprehensively revised to reflect shifts towards transdiagnostic practice, co-design principles, and personalized medicine, and features new chapters on low intensity psychological interventions and private practice. Fully updated for the DSM-5 and ICD-11, provides readers with a contemporary account of diagnoses. It covers practical skills such as interviewing, diagnosis, assessment, case formulation, treatment, case management, and process issues with emphasis on the question ‘how would a scientist-practitioner think and act?’ The book equips trainees to deliver the accountable, efficient, and effective client-centred service demanded of professionals in the modern integrated care setting by demonstrating how an evidence-base can influence every decision of a clinical psychologist. Essential reading for all those enrolled in, or contemplating, postgraduate studies in clinical psychology.