One in five children in a kindergarten class is at risk for mental health problems. By making a diagnosis as early as possible, the child may receive targeted support and be strengthened in his or her further development. This textbook aims at increasing competence in the expert treatment of mental disorders and behavioral problems in early childhood. After a compact presentation of child development in the first six years of life, possible clinical disorders are presented, stringently structured according to classification, prevalence, causes, diagnosis, and therapy. The disorders that are covered in this book include autism spectrum disorders, ADHD, anxiety and obsessive-compulsive disorders, affective disorders, sleep, eating, and crying disorders, trauma, stress, and deprivation disorders, and attachment and relationship disorders of early childhood.