第15章心理的障害

Dissociative disorders are characterized by an individual becoming split off, or dissociated, from their core sense of self. Memory and identity become disturbed; these disturbances have a psychological rather than physical cause. Dissociative disorders listed in the DSM-5 include dissociative amnesia, depersonalization/derealization disorder, and dissociative identity disorder.

Amnesia refers to the partial or total forgetting of some experience or event. An individual with dissociative amnesia is unable to recall important personal information, usually following an extremely stressful or traumatic experience such as combat, natural disasters, or being the victim of violence. The memory impairments are not caused by ordinary forgetting. Some individuals with dissociative amnesia will also experience dissociative fugue (from the word “to flee” in French), whereby they suddenly wander away from their home, experience confusion about their identity, and sometimes even adopt a new identity (Cardeña & Gleaves, 2006). Most fugue episodes last only a few hours or days, but some can last longer. One study of residents in communities in upstate New York reported that about 1.8% experienced dissociative amnesia in the previous year (Johnson, Cohen, Kasen, & Brook, 2006).

Some have questioned the validity of dissociative amnesia (Pope, Hudson, Bodkin, & Oliva, 1998); it has even been characterized as a “piece of psychiatric folklore devoid of convincing empirical support” (McNally, 2003, p. 275). Notably, scientific publications regarding dissociative amnesia rose during the 1980s and reached a peak in the mid-1990s, followed by an equally sharp decline by 2003; in fact, only 13 cases of individuals with dissociative amnesia worldwide could be found in the literature that same year (Pope, Barry, Bodkin, & Hudson, 2006). Further, no description of individuals showing dissociative amnesia following a trauma exists in any fictional or nonfictional work prior to 1800 (Pope, Poliakoff, Parker, Boynes, & Hudson, 2006). However, a study of 82 individuals who enrolled for treatment at a psychiatric outpatient hospital found that nearly 10% met the criteria for dissociative amnesia, perhaps suggesting that the condition is underdiagnosed, especially in psychiatric populations (Foote, Smolin, Kaplan, Legatt, & Lipschitz, 2006).

Depersonalization/derealization disorder is characterized by recurring episodes of depersonalization, derealization, or both. Depersonalization is defined as feelings of “unreality or detachment from, or unfamiliarity with, one’s whole self or from aspects of the self” (APA, 2013, p. 302). Individuals who experience depersonalization might believe their thoughts and feelings are not their own; they may feel robotic as though they lack control over their movements and speech; they may experience a distorted sense of time and, in extreme cases, they may sense an “out-of-body” experience in which they see themselves from the vantage point of another person. Derealization is conceptualized as a sense of “unreality or detachment from, or unfamiliarity with, the world, be it individuals, inanimate objects, or all surroundings” (APA, 2013, p. 303). A person who experiences derealization might feel as though they are in a fog or a dream, or that the surrounding world is somehow artificial and unreal. Individuals with depersonalization/derealization disorder often have difficulty describing their symptoms and may think they are going crazy (APA, 2013).

The most well-known dissociative disorder is dissociative identity disorder (formerly called multiple personality disorder). People with dissociative identity disorder exhibit two or more separate personality states, each distinct from one another in affect, behavior, consciousness, memory, perception, cognition, and/or sensory-motor functioning. They may or may not experience memory gaps for the time during which another identity is controlling the body (e.g., one might find unfamiliar items in their shopping bags or among their possessions). In order to fit criteria for the diagnosis, they must experience disruptions in memory (of traumatic events, daily events, and/or personal information) that is more serious than ordinary forgetting. Some people with DID can talk internally with the other personality states, which can resemble voice-hearing (APA, 2013). The study of upstate New York residents mentioned above (Johnson et al., 2006) reported that 1.5% of their sample experienced symptoms consistent with dissociative identity disorder in the previous year.

DID is sometimes viewed as controversial because rates of the disorder suddenly skyrocketed in the 1980s. More cases of DID were identified during the five years prior to 1986 than in the preceding two centuries (Putnam, Guroff, Silberman, Barban, & Post, 1986). Although this increase may be due to the development of more sophisticated diagnostic techniques, it is also possible that the popularization of DID—helped in part by Sybil, a popular 1970s book (and later film) about a woman with 16 different personalities—may have prompted clinicians to overdiagnose the disorder (Piper & Merskey, 2004). For example, the False Memory Foundation, founded by family members who were accused of childhood abuse, cast doubt on the validity of the disorder (Pope, 1996). To this day, many psychologists do not believe that DID is anything but iatrogenic (induced by therapists looking for the disorder). However, for people with this disorder who report a history of childhood trauma, a number of cases have been corroborated through medical or legal records (Cardeña & Gleaves, 2006).

Beyond the 1990s, research using brain scans has revealed significant differences between fMRIs of people diagnosed with DID and control subjects who were told to fake DID during the scan, further corroborating that DID is a legitimate condition (Reinders et al., 2019). Research into DID continues to explore avenues of childhood trauma, attachment, genetics, and environmental influences in the cause of this disorder (Dell & O’Neil, 2009). For example, there is strong evidence that traumatic experiences can cause people to experience states of dissociation, suggesting that dissociative states—including the adoption of multiple personalities—may serve as a psychologically important coping mechanism for threat and danger (Dalenberg et al., 2012). Additionally, not all people who experience multiple personality states consider their condition to be disordered or caused by trauma. Qualitative research has begun to delve into non-pathological multiplicity spectrum experiences in addition to people who are suffering from DID, enriching psychologists’ understanding of this misunderstood condition (Eve, Heyes, & Parry, 2023).