Dissociation can be defined as the failure to integrate experience. Dissociation is a common symptom of a spectrum of severe psychopathologies, from reactive attachment disorder of infants to dissociative identity disorders, psychotic experiences, borderline personality disorders and post-traumatic stress disorders of adults. The incidence of abuse in the childhood histories of adults with dissociative disorders is extremely high. The adaptational value of dissociation is that it allows survival in catastrophic events. The disadvantage is that when dissociation occurs frequently, the development of neural networks is impaired. Especially disadvantageous are problems which develop with a) higher circuit control over lower circuits, b) primitive parasympathetic regulation by the dorsal motor nucleus, c) memory, d) left hemisphere, e) integration of bodily sensations, f) sense of self, and g) affect and motivation. These aspects are discussed in more detail. The clinician's primary function is as an affect regulator and therapy should focus on integration.