As you have just read, people with acute and posttraumatic stress disorders may have symptoms of dissociation along with their other symptoms. They may, for example, feel dazed, have trouble remembering things, or have a sense of derealization. Symptoms of this kind are also on display in dissociative disorders, another group of disorders triggered by traumatic events (Armour et al., 2014). In fact, the memory difficulties and other dissociative symptoms found in these disorders are particularly intense, extensive, and disruptive. Moreover, in such disorders, dissociative reactions are the main or only symptoms. People with dissociative disorders do not typically have the significant arousal, negative emotions, sleep difficulties, and other problems that characterize acute and posttraumatic stress disorders. Nor are there clear physical factors at work in dissociative disorders.

Most of us experience a sense of wholeness and continuity as we interact with the world. We perceive ourselves as being more than a collection of isolated sensory experiences, feelings, and behaviors. In other words, we have an identity, a sense of who we are and where we fit in our environment. Memory is a key to this sense of identity, the link between our past, present, and future. Without a memory, we would always be starting over; with it, our life and our identity move forward. In dissociative disorders, one part of a person’s memory or identity becomes dissociated, or separated, from other parts of his or her memory or identity.

There are several kinds of dissociative disorders. People with dissociative amnesia are unable to recall important personal events and information. People with dissociative identity disorder, once known as multiple personality disorder, have two or more separate identities that may not always be aware of each other’s memories, thoughts, feelings, and behavior. And people with depersonalization-derealization disorder feel as though they have become detached from their own mental processes or bodies or are observing themselves from the outside.

Several famous books and movies have portrayed dissociative disorders. Two classics are The Three Faces of Eve and Sybil, each about a woman who developed multiple personalities after having been subject to traumatic events in childhood. The topic is so fascinating that most television drama series seem to include at least one case of dissociation every season, creating the impression that the disorders are very common. Many clinicians, however, believe that they are rare.

People with dissociative amnesia are unable to recall important information, usually of a stressful nature, about their lives (APA, 2013). The loss of memory is much more extensive than normal forgetting and is not caused by physical factors such as a blow to the head (see Table 5.3). Typically, an episode of amnesia is directly triggered by a traumatic or upsetting event (Kikuchi et al., 2010).

Dissociative amnesia may be localized, selective, generalized, or continuous. In localized amnesia, the most common type of dissociative amnesia, a person loses all memory of events that took place within a limited period of time, almost always beginning with some very disturbing occurrence. A soldier, for example, may awaken a week after a horrific combat battle and be unable to recall the battle or any of the events surrounding it. She may remember everything that happened up to the battle and may recall everything that has occurred over the past several days, but the events in between remain a total blank. The forgotten period is called the amnestic episode. During an amnestic episode, people may appear confused; in some cases they wander about aimlessly. They are already experiencing memory difficulties but seem unaware of them.

People with selective amnesia, the second most common form of dissociative amnesia, remember some, but not all, events that took place during a period of time. If the combat soldier mentioned in the previous paragraph had selective amnesia, she might remember certain interactions or conversations that occurred during the battle, but not more disturbing events such as the death of a friend or the screams of enemy soldiers.

In some cases the loss of memory extends back to times long before the upsetting period. In addition to forgetting battle-linked events, the soldier may not remember events that occurred earlier in her life. In this case, she would have what is called generalized amnesia. In extreme cases, she might not even recognize relatives and friends.

In the forms of dissociative amnesia just discussed, the period affected by the amnesia has an end. In continuous amnesia, however, forgetting continues into the present. The soldier might forget new and ongoing experiences as well as what happened before and during the battle.

These various forms of dissociative amnesia are similar in that the amnesia interferes mostly with a person’s memory of personal material. Memory for abstract or encyclopedic information usually remains. People with dissociative amnesia are as likely as anyone else to know the name of the president of the United States and how to read or drive a car.

Clinicians do not know how common dissociative amnesia is (Pope et al., 2007), but they do know that many cases seem to begin during serious threats to health and safety, as in wartime and natural disasters. Like the soldier in the earlier examples, combat veterans often report memory gaps of hours or days, and some forget personal information, such as their name and address (Bremner, 2002).

Childhood abuse, particularly child sexual abuse, can also trigger dissociative amnesia; indeed, in the 1990s there were many reports in which adults claimed to recall long-forgotten experiences of childhood abuse (Wolf & Nochajski, 2013) (see PsychWatch below). In addition, dissociative amnesia may occur under more ordinary circumstances, such as the sudden loss of a loved one through rejection or death or extreme guilt over certain actions (for example, an extramarital affair) (Koh et al., 2000).

The personal impact of dissociative amnesia depends on how much is forgotten. Obviously, an amnestic episode of two years is more of a problem than one of two hours. Similarly, an amnestic episode during which a person’s life changes in major ways causes more difficulties than one that is quiet.

An extreme version of dissociative amnesia is called dissociative fugue. Here persons not only forget their personal identities and details of their past lives but also flee to an entirely different location. Some people travel a short distance and make few social contacts in the new setting (APA, 2013). Their fugue may be brief—a matter of hours or days—and end suddenly. In other cases, however, the person may travel far from home, take a new name, and establish a new identity, new relationships, and even a new line of work. Such people may also display new personality characteristics; often they are more outgoing. This pattern is seen in the century-old case of the Reverend Ansel Bourne, whose last name was the inspiration for Jason Bourne, the memory-deprived secret agent in the modern-day Bourne books and movies.

Fugues tend to end abruptly. In some cases, as with Reverend Bourne, the person “awakens” in a strange place, surrounded by unfamiliar faces, and wonders how he or she got there. In other cases, the lack of personal history may arouse suspicion. Perhaps a traffic accident or legal problem leads police to discover the false identity; at other times friends search for and find the missing person. When people are found before their state of fugue has ended, therapists may find it necessary to ask them many questions about the details of their lives, repeatedly remind them who they are, and even begin psychotherapy before they recover their memories (Igwe, 2013; Mamarde et al., 2013). As these people recover their past, some forget the events of the fugue period.

The majority of people who go through a dissociative fugue regain most or all of their memories and never have a recurrence. Since fugues are usually brief and totally reversible, those who have experienced them tend to have few aftereffects. People who have been away for months or years, however, often do have trouble adjusting to the changes that took place during their flight. In addition, some people commit illegal or violent acts in their fugue state and later must face the consequences.

Dissociative identity disorder is both dramatic and disabling, as we see in the case of Luisa:

A person with dissociative identity disorder, known in the past as multiple personality disorder, develops two or more distinct personalities, often called subpersonalities, or alternate personalities, each with a unique set of memories, behaviors, thoughts, and emotions (see again Table 5.3). At any given time, one of the subpersonalities takes center stage and dominates the person’s functioning. Usually one subpersonality, called the primary, or host, personality, appears more often than the others.

The transition from one subpersonality to another, called switching, is usually sudden and may be dramatic (Barlow & Chu, 2014). Luisa, for example, twisted her face and hunched her shoulders and body forward violently. Switching is usually triggered by a stressful event, although clinicians can also bring about the change with hypnotic suggestion.

Cases of dissociative identity disorder were first reported almost three centuries ago (Rieber, 2006, 2002). Many clinicians consider the disorder to be rare, but some reports suggest that it may be more common than was once thought (Dorahy et al., 2014). Most cases are first diagnosed in late adolescence or early adulthood, but more often than not, the symptoms actually began in early childhood after episodes of trauma or abuse (often sexual abuse) (Sar et al., 2014; Steele, 2011; Ross & Ness, 2010). Women receive this diagnosis at least three times as often as men.

How Do Subpersonalities Interact? How subpersonalities relate to or recall one another varies from case to case (Barlow & Chu, 2014). Generally, however, there are three kinds of relationships. In mutually amnesic relationships, the subpersonalities have no awareness of one another (Ellenberger, 1970). Conversely, in mutually cognizant patterns, each subpersonality is well aware of the rest. They may hear one another’s voices and even talk among themselves. Some are on good terms, while others do not get along at all.

In one-way amnesic relationships, the most common relationship pattern, some subpersonalities are aware of others, but the awareness is not mutual. Those who are aware, called coconscious subpersonalities, are “quiet observers” who watch the actions and thoughts of the other subpersonalities but do not interact with them. Sometimes while another subpersonality is present, the coconscious personality makes itself known through indirect means, such as auditory hallucinations (perhaps a voice giving commands) or “automatic writing” (the current personality may find itself writing down words over which it has no control).

Investigators used to believe that most cases of dissociative identity disorder involved two or three subpersonalities. Studies now suggest, however, that the average number of subpersonalities per patient is much higher—15 for women and 8 for men (APA, 2000). In fact, there have been cases in which 100 or more subpersonalities were observed. Often the subpersonalities emerge in groups of two or three at a time.

In the case of “Eve White,” made famous in the book and movie The Three Faces of Eve, a woman had three subpersonalities—Eve White, Eve Black, and Jane (Thigpen & Cleckley, 1957). Eve White, the primary personality, was quiet and serious; Eve Black was carefree and mischievous; and Jane was mature and intelligent. According to the book, these three subpersonalities eventually merged into Evelyn, a stable personality who was really an integration of the other three.

The book was mistaken, however; this was not to be the end of Eve’s dissociation. In an autobiography 20 years later, she revealed that altogether 22 subpersonalities had come forth during her life, including 9 subpersonalities after Evelyn. Usually they appeared in groups of three, and so the authors of The Three Faces of Eve apparently never knew about her previous or subsequent subpersonalities. She has now overcome her disorder, achieving a single, stable identity, and has been known as Chris Sizemore for more than 35 years (Ramsland & Kuter, 2011; Sizemore, 1991).

How Do Subpersonalities Differ? As in Chris Sizemore’s case, subpersonalities often exhibit dramatically different characteristics. They may also have their own names and different identifying features, abilities and preferences, and even physiological responses.

IDENTIFYING FEATURES The subpersonalities may differ in features as basic as age, gender, race, and family history, as in the case of Sybil Dorsett, whose disorder is described in the famous novel Sybil (Schreiber, 1973). According to the novel, Sybil displayed 17 subpersonalities, all with different identifying features. They included adults, a teenager, and even a baby. One subpersonality, Vicky, saw herself as attractive and blonde, while another, Peggy Lou, believed herself to be “a pixie with a pug nose.” Yet another, Mary, was plump with dark hair, and Vanessa was a tall, thin redhead. (It is worth noting that the accuracy of the real-life case on which this novel was based has been challenged in recent years.)

ABILITIES AND PREFERENCES Although memories of abstract or encyclopedic information are not usually affected in dissociative amnesia, they are often disturbed in dissociative identity disorder. It is not uncommon for the different subpersonalities to have different abilities: one may be able to drive, speak a foreign language, or play a musical instrument, while the others cannot (Coons & Bowman, 2001). Their handwriting can also differ. In addition, the subpersonalities usually have different tastes in food, friends, music, and literature. Chris Sizemore (“Eve”) later pointed out, “If I had learned to sew as one personality and then tried to sew as another, I couldn’t do it. Driving a car was the same. Some of my personalities couldn’t drive” (Sizemore & Pitillo, 1977, p. 4).

PHYSIOLOGICAL RESPONSES Researchers have discovered that subpersonalities may have physiological differences, such as differences in blood pressure levels and allergies (Spiegel, 2009; Putnam et al., 1990). A pioneering study looked at the brain activities of different subpersonalities by measuring their evoked potentials—that is, brain-response patterns recorded on an electroencephalograph (Putnam, 1984). The brain pattern a person produces in response to a specific stimulus (such as a flashing light) is usually unique and consistent. However, when an evoked potential test was administered to four subpersonalities of each of 10 people with dissociative identity disorder, the results were dramatic. The brain-activity pattern of each subpersonality was unique, showing the kinds of variations usually found in totally different people. A number of other studies conducted over the past two decades have yielded similar findings (Boysen & VanBergen, 2014).

How Common Is Dissociative Identity Disorder? As you have seen, dissociative identity disorder has traditionally been thought of as rare. Some researchers even argue that many or all cases are iatrogenic—that is, unintentionally produced by practitioners (Lynn & Deming, 2010; Piper & Merskey, 2005, 2004). They believe that therapists create this disorder by subtly suggesting the existence of other personalities during therapy or by explicitly asking a patient to produce different personalities while under hypnosis. In addition, they believe, a therapist who is looking for multiple personalities may reinforce these patterns by displaying greater interest when a patient displays symptoms of dissociation.

These arguments seem to be supported by the fact that many cases of dissociative identity disorder first come to attention while the person is already in treatment for a less serious problem. But such is not true of all cases; many people seek treatment because they have noticed time lapses throughout their lives or because relatives and friends have observed their subpersonalities (Putnam, 2006, 2000).

The number of people diagnosed with dissociative identity disorder increased dramatically in the 1980s and 1990s, only to decrease again over the past 15 years (Paris, 2012). Not withstanding this decline, thousands of cases have now been diagnosed in the United States and Canada alone, and some clinical theorists estimate that as much as 1 percent of the population in the United States and other Western countries displays the disorder (Dorahy et al., 2014). On the other side of the coin, many clinicians continue to question the legitimacy of this category.

A variety of theories have been proposed to explain dissociative amnesia and dissociative identity disorder. Older explanations, such as those offered by psychodynamic and behavioral theorists, have not received much investigation (Merenda, 2008). However, newer viewpoints, which combine cognitive-behavioral and biological principles and highlight such factors as state-dependent learning and self-hypnosis, have captured the interest of clinical scientists.

The Psychodynamic View Psychodynamic theorists believe that these dissociative disorders are caused by repression, the most basic ego defense mechanism: people fight off anxiety by unconsciously preventing painful memories, thoughts, or impulses from reaching awareness. Everyone uses repression to a degree, but people with dissociative amnesia and dissociative identity disorder are thought to repress their memories excessively (Henderson, 2010).

In the psychodynamic view, dissociative amnesia is a single episode of massive repression. A person unconsciously blocks the memory of an extremely upsetting event to avoid the pain of facing it (Kikuchi et al., 2010). Repressing may be his or her only protection from overwhelming anxiety.

In contrast, dissociative identity disorder is thought to result from a lifetime of excessive repression (Howell, 2011; Wang & Jiang, 2007). Psychodynamic theorists believe that this continuous use of repression is motivated by traumatic childhood events, particularly abusive parenting (Baker, 2010; Ross & Ness, 2010). Children who experience such traumas may come to fear the dangerous world they live in and take flight from it by pretending to be another person who is looking on safely from afar. Abused children may also come to fear the impulses that they believe are the reasons for their excessive punishments. Whenever they experience “bad” thoughts or impulses, they unconsciously try to disown and deny them by assigning them to other personalities.

Most of the support for the psychodynamic explanation of dissociative identity disorder is drawn from case histories, which report such brutal childhood experiences as beatings, cuttings, burnings with cigarettes, imprisonment in closets, rape, and extensive verbal abuse (Ross & Ness, 2010). Yet some individuals with this disorder do not seem to have experiences of abuse in their background (Ross & Ness, 2010; Bliss, 1980). For example, Chris Sizemore, the subject of The Three Faces of Eve, has reported that her disorder first emerged during her preschool years after she witnessed two deaths and a horrifying accident within a three-month period.

The Behavioral View Behaviorists believe that dissociation grows from normal memory processes such as drifting of the mind or forgetting (see PsychWatch on page 175). Specifically, they hold that dissociation is a response learned through operant conditioning (Casey, 2001). People who experience a horrifying event may later find temporary relief when their mind drifts to other subjects. For some, this momentary forgetting, leading to a drop in anxiety, increases the likelihood of future forgetting. In short, they are reinforced for the act of forgetting and learn—without being aware that they are learning—that such acts help them escape anxiety. Thus, like psychodynamic theorists, behaviorists see dissociation as escape behavior. But behaviorists believe that a reinforcement process rather than a hardworking unconscious is keeping the individuals unaware that they are using dissociation as a means of escape. Like psychodynamic theorists, behaviorists have relied largely on case histories to support their view. Moreover, the behavioral explanation fails to explain precisely how temporary and normal escapes from painful memories grow into a complex disorder or why more people do not develop dissociative disorders.

State-Dependent Learning If people learn something when they are in a particular situation or state of mind, they are likely to remember it best when they are again in that same condition. If they are given a learning task while under the influence of alcohol, for example, their later recall of the information may be strongest under the influence of alcohol. Similarly, if they smoke cigarettes while learning, they may later have better recall when they are again smoking.

This link between state and recall is called state-dependent learning. It was initially observed in animals who learned things during experiments while under the influence of certain drugs (Ardjmand et al., 2011; Overton, 1966, 1964). Research with human participants later showed that state-dependent learning can be associated with mood states as well: material learned during a happy mood is recalled best when the participant is again happy, and sad-state learning is recalled best during sad states (de l’Etoile, 2002; Bower, 1981) (see Figure 5.3).

What causes state-dependent learning? One possibility is that arousal levels are an important part of learning and memory. That is, a particular level of arousal will have a set of remembered events, thoughts, and skills attached to it. When a situation produces that particular level of arousal, the person is more likely to recall the memories linked to it.

Although people may remember certain events better in some arousal states than in others, most can recall events under a variety of states. However, perhaps people who are prone to develop dissociative disorders have state-to-memory links that are unusually rigid and narrow (Barlow, 2011). Maybe each of their thoughts, memories, and skills is tied exclusively to a particular state of arousal, so that they recall a given event only when they experience an arousal state almost identical to the state in which the memory was first acquired. When such people are calm, for example, they may forget what happened during stressful times, thus laying the groundwork for dissociative amnesia. Similarly, in dissociative identity disorder, different arousal levels may produce entirely different groups of memories, thoughts, and abilities—that is, different subpersonalities (Dorahy & Huntjens, 2007). This could explain why personality transitions in dissociative identity disorder tend to be sudden and stress-related.

Self-Hypnosis As you first saw in Chapter 1, people who are hypnotized enter a sleeplike state in which they become very suggestible. While in this state, they can behave, perceive, and think in ways that would ordinarily seem impossible. They may, for example, become temporarily blind, deaf, or insensitive to pain. Hypnosis can also help people remember events that occurred and were forgotten years ago, a capability used by many psychotherapists. Conversely, it can make people forget facts, events, and even their personal identities—an effect called hypnotic amnesia.

The parallels between hypnotic amnesia and the dissociative disorders we have been examining are striking (van der Kruijs et al., 2014). Both are conditions in which people forget certain material for a period of time yet later remember it. And in both, the people forget without any insight into why they are forgetting or any awareness that something is being forgotten. These parallels have led some theorists to conclude that dissociative disorders may be a form of self-hypnosis in which people hypnotize themselves to forget unpleasant events (Dell, 2010). Dissociative amnesia may develop, for example, in people who, consciously or unconsciously, hypnotize themselves into forgetting horrifying experiences that have recently taken place in their lives. If the self-induced amnesia covers all memories of a person’s past and identity, that person may undergo a dissociative fugue.

The self-hypnosis theory might also be used to explain dissociative identity disorder. On the basis of several investigations, some theorists believe that this disorder often begins between the ages of 4 and 6, a time when children are generally very suggestible and excellent hypnotic subjects (Kohen & Olness, 2011; Kluft, 2001, 1987). These theorists argue that some children who experience abuse or other horrifying events manage to escape their threatening world by self-hypnosis, mentally separating themselves from their bodies and fulfilling their wish to become some other person or persons (Giesbrecht & Merckelbach, 2009). One patient with multiple personalities observed, “I was in a trance often [during my childhood]. There was a little place where I could sit, close my eyes and imagine, until I felt very relaxed just like hypnosis” (Bliss, 1980, p. 1392).

As you have seen, people with dissociative amnesia often recover on their own. Only sometimes do their memory problems linger and require treatment. In contrast, people with dissociative identity disorder usually require treatment to regain their lost memories and develop an integrated personality. Treatments for dissociative amnesia tend to be more successful than those for dissociative identity disorder, probably because the former pattern is less complex.

How Do Therapists Help People with Dissociative Amnesia? The leading treatments for dissociative amnesia are psychodynamic therapy, hypnotic therapy, and drug therapy, although support for these interventions comes largely from case studies rather than controlled investigations (Gentile et al., 2014, 2013). Psychodynamic therapists guide patients to search their unconscious in the hope of bringing forgotten experiences back to consciousness (Howell, 2011). The focus of psychodynamic therapy seems particularly well suited to the needs of people with dissociative amnesia. After all, the patients need to recover lost memories, and the general approach of psychodynamic therapists is to try to uncover memories—as well as other psychological processes—that have been repressed. Thus many theorists, including some who do not ordinarily favor psychodynamic approaches, believe that psychodynamic therapy may be the most appropriate treatment for dissociative amnesia.

Another common treatment for dissociative amnesia is hypnotic therapy, or hypnotherapy. Therapists hypnotize patients and then guide them to recall their forgotten events (Rathbone et al., 2014). Given the possibility that dissociative amnesia may be a form of self-hypnosis, hypnotherapy may be a particularly useful intervention. It has been applied both alone and in combination with other approaches (Colletti et al., 2010).

Sometimes injections of barbiturates such as sodium amobarbital (Amytal) or sodium pentobarbital (Pentothal) have been used to help patients with dissociative amnesia regain their lost memories. These drugs are often called “truth serums,” but actually their effect is to calm people and free their inhibitions, thus helping them to recall anxiety-producing events (Ahern et al., 2000). These drugs do not always work, however, and if used at all, they are likely to be combined with other treatment approaches.

How Do Therapists Help People with Dissociative Identity Disorder? Unlike victims of dissociative amnesia, people with dissociative identity disorder do not typically recover without treatment. Treatment for this pattern is complex and difficult, much like the disorder itself. Therapists usually try to help the clients (1) recognize fully the nature of their disorder, (2) recover the gaps in their memory, and (3) integrate their subpersonalities into one functional personality (Gentile et al., 2014, 2013; Howell, 2011).

RECOGNIZING THE DISORDER Once a diagnosis of dissociative identity disorder is made, therapists typically try to bond with the primary personality and with each of the subpersonalities (Howell, 2011). As bonds are formed, therapists try to educate patients and help them to recognize fully the nature of their disorder. Some therapists actually introduce the subpersonalities to one another, by hypnosis, for example, or by having patients look at videos of their other personalities (Howell, 2011; Ross & Gahan, 1988). A number of therapists have also found that group therapy helps to educate patients (Fine & Madden, 2000). In addition, family therapy may be used to help educate spouses and children about the disorder and to gather helpful information about the patient (Kluft, 2001, 2000).

RECOVERING MEMORIES To help patients recover the missing pieces of their past, therapists typically use the same approaches applied in dissociative amnesia, including psychodynamic therapy, hypnotherapy, and drug treatment (Brand et al., 2014; Kluft, 2001, 1991). These techniques work slowly for patients with dissociative identity disorder, however, as some subpersonalities may keep denying experiences that the others recall. One of the subpersonalities may even assume a “protector” role to prevent the primary personality from suffering the pain of recollecting traumatic experiences.

INTEGRATING THE SUBPERSONALITIES The final goal of therapy is to merge the different subpersonalities into a single, integrated identity. Integration is a continuous process that occurs throughout treatment until patients “own” all of their behaviors, emotions, sensations, and knowledge. Fusion is the final merging of two or more subpersonalities. Many patients distrust this final treatment goal, and their subpersonalities may see integration as a form of death (Howell, 2011; Kluft, 2001, 1991). Therapists have used a range of approaches to help merge subpersonalities, including psychodynamic, supportive, cognitive, and drug therapies (Cronin et al., 2014; Baker, 2010).

Once the subpersonalities are integrated, further therapy is typically needed to maintain the complete personality and to teach social and coping skills that may help prevent later dissociations. In case reports, some therapists note high success rates (Brand et al., 2014; Dorahy et al., 2014), but others find that patients continue to resist full integration. A few therapists have in fact questioned the need for full integration.

As you read earlier, DSM-5 categorizes depersonalization-derealization disorder as a dissociative disorder, even though it is not characterized by the memory difficulties found in the other dissociative disorders. Its central symptoms are persistent and recurrent episodes of depersonalization (the sense that one’s own mental functioning or body is unreal or detached) and/or derealization (the sense that one’s surroundings are unreal or detached).

Like this graduate student, people experiencing depersonalization feel as though they have become separated from their body and are observing themselves from outside. Occasionally their mind seems to be floating a few feet above them—a sensation known as doubling. Their body parts feel foreign to them, their hands and feet smaller or bigger than usual. Many sufferers describe their emotional state as “mechanical,” “dreamlike,” or “dizzy.” Throughout the whole experience, however, they are aware that their perceptions are distorted, and in that sense they remain in contact with reality. In some cases this sense of unreality also extends to other sensory experiences and behavior. People may, for example, have distortions in their sense of touch or smell or their judgments of time or space, or they may feel that they have lost control over their speech or actions.

In contrast to depersonalization, derealization is characterized by feeling that the external world is unreal and strange. Objects may seem to change shape or size; other people may seem removed, mechanical, or even dead. The graduate student, for example, saw other people as robots, perceived his girlfriend in a distorted manner, and hesitated to return for a second session of therapy because he wondered whether his therapist was really alive.

Depersonalization and derealization experiences by themselves do not indicate a depersonalization-derealization disorder. Transient depersonalization or derealization reactions are fairly common (Michal, 2011). One-third of all people say that on occasion they have felt as though they were watching themselves in a movie. Similarly, one-third of individuals who confront a life-threatening danger experience feelings of depersonalization or derealization (van Duijl et al., 2010). People sometimes have feelings of depersonalization after practicing meditation or after traveling to new places. Young children may also experience depersonalization from time to time as they are developing their capacity for self-awareness. In most such cases, the affected people are able to compensate for the distortion and continue to function with reasonable effectiveness until the temporary episode eventually ends.

The symptoms of depersonalization-derealization disorder, in contrast, are persistent or recurrent, cause considerable distress, and may impair social relationships and job performance (Gentile et al., 2014; Michal, 2011). The disorder occurs most frequently in adolescents and young adults, hardly ever in people over 40 (Moyano, 2010). It usually comes on suddenly and may be triggered by extreme fatigue, physical pain, intense stress, or recovery from substance abuse. Survivors of traumatic experiences or people caught in life-threatening situations, such as hostages or kidnap victims, seem to be particularly vulnerable to this disorder. The disorder tends to be long-lasting; the symptoms may improve and even disappear for a time, only to return or intensify during times of severe stress. Like the graduate student in our case discussion, many sufferers fear that they are losing their minds and become preoccupied with worry about their symptoms. Few theories have been offered to explain this disorder.