ear Colleagues,The fact that we have devoted an issue of Dialogues in Clinical Neuroscience to child and ado-lescent psychiatry reflects the fact that this is an area of psychiatry with features that differentiate itfrom that of young and older adults.Indeed, we are able to note that, though the great majority of symptoms remain the samethroughout the different age groups, they are organized differently, and in this way lead to syndromeswith different patterns.Moreover, the circumstances of onset, the triggering mechanisms, the reinforcing factors, andthe types of therapeutic strategies used also set a particular tone for child and adolescent psychiatricsemiology, and bestow certain features upon it.Finally, some classes of symptoms, though not entirely absent in adults, are nevertheless morecharacteristic of children or adolescents; for example, attention deficit-hyperactivity disorder, sometypes of sleep disturbances (nightmares, sleepwalking, sleep epilepsy, bruxism), anorexia nervosa, etc.We felt that it was important to place these disorders in their context, and to emphasize theclinical elements which distinguish psychiatry in this younger population.This is also an era in which the use in younger patients of treatments designed for adults andthe elderly is being greatly questioned. Many authors are strongly emphasizing the need for studiesto be carried out to validate these therapeutic strategies in children and adolescents, and for the devel-opment of therapeutic strategies for particular disorders.This requires a more profound clinical knowledge of children and adolescents, whether via spe-cific studies in younger patients when we wish to use treatments that are already available, or on theother hand via the inclusion of child and adolescent indications in the planning of product develop-ment.Nancy Andreasen, with the assistance of Debbie Morris-Rosendahl, agreed to coordinate thisissue, which provides some responses to the questions discussed. It was a difficult task, and we thankthem both very much for addressing it in such a clear and intelligent manner.We would also like to warmly thank the various authors who agreed to contribute their skillsand knowledge to the production of this issue.Best regards,Jean-Paul Macher, MDE d i t o r i a lD