[Nosology, assessment and diagnosis of psychiatric disorders in early childhood]

The first 5 years of life, the period called "early childhood", are characterized by a dynamic process of development and maturation of the central nervous system (CNS). This process is manifested by continuous changes in cognitive, motor, speech/language, psychological and sensory modulation skills and consequently, in the behavior of the developing child. It is a period of neuron-plasticity, in which the CNS structure and functioning are very sensitive to environmental influences. These influences could be positive or negative. On the one hand, early protective factors, like secure attachment, increase the resilience of the very young child against stressors and against the development of psychopathology; but on the other hand, there is a high vulnerability to early insults of any kind. It has been demonstrated that a high percentage of psychopathology in adult life has his roots in early childhood, and that early diagnosis, which leads to early therapeutic interventions, decreases morbidity and the later life consequences of the disorders. These findings have promoted the field of early childhood psychiatry during the last decade, to become one of the most promising challenges in the field of mental health. In our review, we present an update on the state of nosology, assessment and diagnosis in early childhood and provide clinical guidelines for the daily work of professionals involved in the mental health care of very young children.