Our child came to us through the foster care system. When they found her, she could not speak, walk, or play. Over the past year, she’s learned to do all those things. She does really well most days, but sometimes the smallest things can undo her. We were driving home from a visit with the case manager who helped get her out of that horrid place, and she just checked out. She was staring right at me, but it was like she wasn’t even there. Later, she asked me how we got home. She didn’t even remember being in the car. —Juan

Dissociation involves a “disconnection or lack of connection between things usually associated with each other” (International Society for the Study of Trauma and Dissociation [ISSTD], 2013b, para. 1) and is a normal part of many life experiences. Everyday dissociation can occur, for example, when an individual is absorbed in an activity, when a child creates an imaginary friend, or when an individual blocks out an unpleasant memory (ISSTD, 2013a). Approximately three quarters of individuals will experience dissociation after a traumatic incident as the brain works to protect itself during times of distress; however, most will not go on to develop dissociative disorders.

Dissociative disorders “are characterized by a disruption of and/or discontinuity in the normal integration of consciousness, memory, identity, emotion, perception, body representation, motor control, and behavior” (APA, 2013, p. 291). Spiegel et al. (2011) described dissociative symptoms as

(a) unbidden and unpleasant intrusions into awareness and behavior, with accompanying losses of continuity in subjective experience: (i.e. “positive” dissociative symptoms); and/or (b) an inability to access information or to control mental functions that normally are readily amenable to access or control: (i.e. “negative” dissociative symptoms). (p. 826)

The ISSTD (2013b) identified five types of dissociation addressed in the DSM-5: depersonalization, derealization, amnesia, identify confusion, and identity alteration. Depersonalization is a “sense of being detached from, or ‘not in’ one’s body,” whereas derealization is a “sense of the world not being real” (ISSTD, 2013b, para. 4) Amnesia involves a loss of ability to access stored information one would be expected to remember (ISSTD, 2013b). Identity confusion involves an uncharacteristic change in one’s sense of self. Identity alteration “is the sense of being markedly different from another part of oneself . . . subtler forms of identity alteration can be observed when a person uses different voice tones, range of language, or facial expressions” (ISSTD, 2013b, para. 7).

There is evidence that dissociative disorders, once considered quite rare or fabricated, are simply missed in clinical settings (Foote, Smolin, Kaplan, Legatt, & Lipschitz, 2006; ISSTD, 2011). Prevalence of this class of disorders is high and estimated at 2% to 10% among the general population (ISSTD, 2013b). Unfortunately, individuals who experience dissociative disorders are among the most vulnerable and high risk of clients. This population experiences near-universal trauma, high rates of comorbid disorders, and suicidal behavior (Brand, Lanius, Vermetten, Loewenstein, & Spiegel, 2012; ISSTD, 2011). This chapter includes a discussion of essential features and special considerations for dissociative identity disorder (DID), dissociative amnesia, and depersonalization/derealization disorder. As with other chapters, the DSM-5 includes other specified dissociative disorder and unspecified dissociative disorder