Dissociative disorders are diagnosed when people habitually and involuntarily escape reality in a way that disrupts their ability to live and work. They occur when a group of normal mental processes becomes separated or dissociated from other mental processes. In this condition, a patient loses conscious control over certain thoughts, feelings and behaviors.

Some aspects of dissociation are a normal part of the human mind. For instance, people may become engrossed in their thoughts while driving and miss a highway exit. The National Mental Health Association (NMHA) reports that up to one-third of the population occasionally feels like they are "watching themselves in a movie." However, continued and repeated incidences of dissociation that interfere with life may be part of a disorder. Such dissociative disorders occur in about 7 percent of people at some point in their lives, according to the NMHA. Most are associated with people who have experienced serious trauma, such as abuse, combat or natural disaster.

There are many different dissociative disorders. They have certain features in common. For example, they tend to begin and end suddenly (although some occur gradually) and often are triggered by psychological conflicts or an absolute inability to tolerate feelings that occur in situations that in some way remind them of past trauma. Most are uncommon and involve significant disturbance of memory. The condition itself may be fleeting, or it may be chronic.

The four major types of dissociative disorders are:

• Dissociative amnesia. Inability to remember important information, especially of a personal nature surrounding significant trauma or stress. Examples include blocking out memories related to episodes of self-mutilation, violent outbursts or suicide attempts. Varieties of dissociative amnesia include:
  
  
• • Localized amnesia. Inability to remember events from a certain time frame.
    
    
  • Selective amnesia. When a patient remembers only select events from a certain time frame.
    
    
  • Generalized amnesia. Inability to recall events over a lifetime.
    
    
  • Continuous amnesia. When a patient cannot recall events from a certain time up to the present.
    
    
• Dissociative fugue. Condition in which patients suddenly leave their surroundings and begin a journey of some type or another that can last from hours to months. Journeys can cover thousands of miles. During this time, patients fail to remember some or all of their past. Patients with dissociative fugue often experience confusion about personal identity and may take on a whole new identity. Although this is rare, it can be dramatic, with patients starting entirely new lives and acting more gregarious and uninhibited than in their previous lives. Traumatic or overwhelming events may trigger dissociative fugue. Patients who are in a state of dissociative fugue appear normal and healthy to outsiders and do not attract attention. Recovery is usually rapid and sudden. People who eventually return to the prefugue state may have no memory of the events that occurred when they had dissociative fugue.
  
  

• Dissociative identity disorder (formerly known as multiple personality disorder). Condition in which two or more distinct identities take control of a patient's behavioral patterns. It is the result of a failure to integrate identity, memory and consciousness. Patients and therapists may identify large numbers of alternate identities (alters), but it is seldom clear which are the result of trauma and which may be created in response to inappropriate therapies. Just one personality (alter) controls a patient's behavior at any given time, and the various alters may have their own personal history, self-image and identity. Despite their apparent differences, alters should always be considered varied aspects of the patient's whole.
  
  Patients with dissociative identity disorder have an inability to recall important personal information, with some alters having less complete memories and other alters recalling more. Psychosocial stress often triggers the transition from one identity to another, although in many cases transition can occur in a wide variety of circumstances, including during relaxation or sleep. In most cases, these changes take just seconds, although the transition can be more gradual.
  
  
• Depersonalization disorder. Condition in which patients experience recurrent episodes of detachment from themselves and tend to experiencing themselves as observing their own behavior from an outside perspective. In other cases, patients may feel detached from control of their bodies and speech patterns. Patients are aware of this sense of detachment. Depersonalization is fairly commonplace, and a disorder is not typically diagnosed unless symptoms cause substantial distress or impair the patient's ability to function. Depersonalization disorder does not involve loss of memory.

Some dissociative disorders are classified as a "dissociative disorder not otherwise specified." These are conditions in which a patient has symptoms of at least one of the above conditions, but not enough symptoms to be diagnosed with any one of these conditions. Examples include dissociation caused by coercion such as brainwashing or among people held as hostages.