Dissociation, or the feeling of being detached from the reality of one's body, can be categorized into two types: depersonalization and derealization. Depersonalization is highlighted by a sense of not knowing who you are, or of questioning long-held beliefs about who you are. In derealization, persons perceive reality in a grossly distorted way. Psychologists have identified several types of disorders based on these feelings. These include depersonalization disorder, dissociative fugue, dissociative amnesia, dissociative trance disorder, and dissociative identity disorder (also known as multiple personality syndrome), among others.
Depersonalization disorder is a condition marked by a persistent feeling of not being real. The DSM-IV describes its symptoms as "persistent or recurrent experiences of feeling detached from, and as if one is an outside observer of, one's mental processes or body (e.g., feeling like one is in a dream)." While many people have experienced a similar feeling, persons actually suffering from this disorder are so overwhelmed by these feelings that they are unable to function normally in society. It is also critical to point out that in order to be diagnosed as having this disorder, these feelings cannot be caused by some specific drug or event. Depersonalization disorder, by itself, is a rare disorder, and, in fact, many of its symptoms are also symptomatic of other more common disorders, such as acute stress disorder and panic attacks.
Dissociative fugue is a strange phenomena in which persons will be stricken with a sudden memory loss that prompts them to flee their familiar surroundings. These flights are usually caused by some traumatic event. People suffering from this disorder will suddenly find themselves in a new surrounding, hundreds or even thousands of miles from their homes with no memories of the weeks, months, or even years that have elapsed since their flight. Incidence of dissociative fugue rarely appear until after adolescence and usually before the age of 50. Once a person has fallen into the behavior, however, it is more likely that it will recur.
Dissociative amnesia describes the condition of suddenly losing major chunks of memory. There are two types of this disorder: generalized amnesia, in which a person cannot remember anything about their lives, and localized amnesia, a common disorder in which a person forgets pieces of their identity but retains an overall understanding of who they are. Dissociative amnesia is generally caused by some traumatic event, such as a natural disaster, a violent crime, or war. In these instances, it is an adaptive mechanism that allows a person to continue his or her life without having to deal with an utterly horrific memory.
Dissociative trance disorder describes the trance-state that people experience in various kinds of religious ceremonies. Such people generally perform feats that would normally cause injury or severe pain-such as walking on hot coals-but because of their dissociated mental state, they are not harmed. This is a curious subcategory in that the condition is not considered a "disorder" in many cultures of the world. Western psychiatrists are divided as to whether this should really be considered a "disorder," since the word has negative implications. It has been proposed, however, that future editions of the DSM specify a diagnosis of trance and possession disorder as one of several dissociative disorders.
Gale Encyclopedia of Psychology, 2nd ed. Gale Group, 2001.