Dissociative disorder is a collective term for four different psychiatric conditions - dissociative amnesia including dissociative fugue, dissociative identity disorder, dissociative derealization and atypical dissociative disorder.
Generally, dissociative disorders develop as a defense measure against psychological trauma. Increased prevalence among child abuse victims, rape cases, war veterans, and survivors of concentration camps or natural disasters has been reported.
Diagnosis rests on clinical findings, questionnaires, hypnosis and several laboratory tests to rule out organic or substance-related causes for dissociative symptoms.
The key finding of dissociative amnesia is the patient's inability to recall specific autobiographical details that are connected with severe stress episodes. Dissociative amnesia causes significant social distress and reduces the quality of life. Amnesia is usually selective but can span several years up to decades depending on the persistence of the traumatic situation. The stronger the stress, the more pronounced the memory loss  . Patients avoid eye contact, show normal activity levels but are aware of their memory loss which may lead to profound frustration. Orientation is normal but anxiety and lack of attentiveness are frequently encountered. Dissociative fugue is a subtype of dissociative amnesia which is characterized by a sudden intentional traveling urge accompanied by dissociative amnesia. Dissociative fugue occurs most often among sexual abuse victims   . Dissociative amnesia can be reversible .
Cases with dissociative identity disorder are easily irritable and anxious while avoiding eye contact; orientation, long- and short-term memory are often impaired. The characteristic finding of dissociative identity disorder, however, is the existence of at least one additional distinct personalities in one patient. These alter egos can differ significantly from the original character in psychological complexity, body posture, language and even sex. Dissociative identity disorder is almost always accompanied by dissociative amnesia and occurs most frequently in victims of child abuse  .
Dissociative derealization has also been associated with childhood trauma and stress situations, in particular long-term emotional maltreatment. Patients experience a surreal detachment of their environment and themselves. Their perception of reality is either blurred or unusually sharp, dull and sometimes systematically distorted. Such patients have the tendency to 'remote-control' other people .
Patients with the atypical dissociative disorder can present with abnormal dialogue behavior, impaired vigilance or hallucinations. It primarily affects men.
Diagnosis of dissociative disorders rests on an analysis of the patient history, clinical criteria and the exclusion of potential causes like substance abuse.
The main criterion for the diagnosis of dissociative amnesia is the trauma-related inability of a victim to recall important personal information causing substantial social distress. Dissociative identity disorder is characterized by the existence of alter egos in addition to dissociative amnesia. A key symptom of dissociative depersonalization is a distorted perception of reality and self .
Psychiatric examinations will reveal these features. Family history analysis should focus on traumatic events like abuse during childhood. Further exams should corroborate the diagnosis by excluding organic causative factors. Electroencephalography (EEG) and magnetic resonance imaging (MRI) procedures can help to rule out physical causes. Substance abuse (e.g. cannabis) can be proven with urinalysis .