According to the polyvagal theory, the autonomic nervous system can, in deviation from the conventional theory, be divided in three distinct parts that are in hierarchical relationship with each other. The most-primitive autonomic control results in depression of vital functions, the more evolved one in fighting or escape and the most evolved one in social involvement. Practical application of the polyvagal theory has resulted in positive results above all in the treatment of emotional trauma. in Finland, therapy of complex trauma is founded on the theory of structural dissociation of the personality, which together with the polyvagal theory forms a practical frame of reference for psychotherapeutic work.