Trauma-Associated Disorders, ADHD, Externalizing and Obsessive-Compulsive Disorders - Mental Health Disorders in Infants, Toddlers, and Preschool Children: Clinical Guideline for Assessment, Counseling and Treatment (Part 3) Abstract: Objective: A wide variety of mental health disorders can affect young children aged 0 to 5;11 years. The aim of revising these interdisciplinary guidelines is to present the current state of knowledge regarding the assessment and therapy of the most important disorders. We formulate consensus-based, practical recommendations. The third part focuses on disorders that primarily affect children over the age of 3 years, specifically trauma-associated disorders, ADHD, externalizing and obsessive-compulsive disorders, and other disorders. Methods: The Guideline Commission consisted of 18 professional associations. The guideline was based on current literature searches and several online consensus conferences, following standard procedures. Results: The prevalence and variety of disorders according to DC: 0 - 5 and/or ICD-10 increase with age among preschool children. Trauma-associated disorders can be highly incapacitating. ADHD and externalizing disorders can become chronic if untreated. Obsessive-compulsive disorders have been overlooked among young children. Counseling should be offered in every case. If indicated, specific psychotherapeutic approaches for each disorder are recommended, involving parents and other caregivers. Except for ADHD, medication is usually not indicated. All disorders can be treated effectively. Conclusions: The recommendations of this guideline were adopted with a high consensus. The recommendations regarding assessment, counseling, and treatment can be implemented effectively in different clinical contexts and by various professional groups.