This book integrates the most recent explanatory models of psychopathology, from RDoC and network theory to transdiagnostic approaches, offering readers a coherent perspective on mental disorders from childhood to old age. Each chapter combines theoretical foundations with concrete clinical applications, vignettes, and empirically validated interventions, facilitating the transfer of knowledge into clinical practice. By connecting child, adult, and elderly psychopathology with contemporary research models, the manual proposes an integrative, non-reductionist view of human psychological suffering.