Background: About 17% of all children suffer from a mental disorder in early childhood, defined as the period up to the age of 6 years.
Methods: This review is based on publications retrieved by a selective search in PubMed and the Web of Science, as well as on the authors' clinical and scientific experience.
Results: In children up to age 2, disorders of emotional and motor regulation are common (ca. 7%), as are feeding problems (25%), which persist in 2% of children to meet the diagnostic criteria for a feeding disorder. Reactive attachment disorder, a serious mental illness, has a prevalence of about 1%: it is more common among children in situations of increased risk, e.g., orphanages and foster homes. Preschool children can develop anxiety disorder and depressive disorder, as well as hyperactivity and behavioral disorders (the latter two mainly in boys). Parent training and parent-child psychotherapy have been found to be effective treatments. There is no evidence that psychotropic drugs are effective in early childhood.
Conclusion: The diagnostician should act cautiously when assigning psychopathological significance to symptoms arising in early childhood but should still be able to recognize mental disorders early from the way they are embedded in the child's interactive relationships with parents or significant others, and then to initiate the appropriate treatment. Psychotherapy in this age group is still in need of validation by efficacy studies and longitudinal studies of adequate quality.