Here is the definition of Developmental Trauma Disorder as outlined by Bessel van der Kolk - Developmental trauma disorder: Towards a rational diagnosis for children with complex trauma histories.

Developmental Trauma Disorder

A. Exposure

1. Multiple or chronic exposure to one or more forms of developmentally adverse interpersonal trauma (abandonment, betrayal, physical assaults, sexual assaults, threats to bodily integrity, coercive practices, emotional abuse, witnessing violence and death).
 
2. Subjective Experience (rage, betrayal, fear, resignation, defeat, shame).
 
B. Triggered pattern of repeated dysregulation in response to trauma cues
Dysregulation (high or low) in presence of cues. Changes persist and do not return to baseline; not reduced in intensity by conscious awareness.

•Affective
•Somatic (physiological, motoric, medical)
•Behavioral (e.g. re-enactment, cutting)
•Cognitive (thinking that it is happening again, confusion, dissociation,
depersonalization).
•Relational (clinging, oppositional, distrustful, compliant).
• Self-attribution (self-hate and blame).

C. Persistently Altered Attributions and Expectancies

•Negative self-attribution
•Distrust protective caretaker
•Loss of expectancy of protection by others
•Loss of trust in social agencies to protect
•Lack of recourse to social justice/retribution
•Inevitability of future victimization

D. Functional Impairment 

•Educational
•Familial
•Peer
•Legal
•Vocational

The research in the ACE study demonstrates how adverse childhood experiences impact later health outcomes on the physical plane, it seems pretty obvious that these experiences also impact mental health.

Responses to a questionnaire about adverse childhood experiences, including childhood abuse, neglect, and family dysfunction, included the following: "11.0% reported having been emotionally abused as a child, 30.1% reported physical abuse, 19.9% sexual abuse; 23.5% reported being exposed to family alcohol abuse, 18.8% to mental illness, 12.5% witnessed their mothers being battered and 4.9% reported family drug abuse." [Felitti VJ, Anda RF, Nordernberg D, et al. (1998). Relationship of childhood abuse to many of the leading causes of death in adults: the adverse childhood experiences (ACE) study. Am J Prev Med.; 14(4): 245-258.]

From the same van der Kolk article cited above, here is the working definition of complex trauma, a similar if not identical condition as developmental trauma disorder (DTD):

The traumatic stress field has adopted the term “Complex Trauma” to describe the experience of multiple and/or chronic and prolonged, developmentally adverse traumatic events, most often of an interpersonal nature (e.g., sexual or physical abuse, war, community violence) and early-life onset. These exposures often occur within the child’s caregiving system and include physical, emotional, and educational neglect and child maltreatment beginning in early childhood (see Cook et al, this issue, Spinazzola et al this issue).

With that background, here is a report on why the DSM-5 committee chose not to include DTD, from Psychotherapy Networker Magazine.

Developmental Trauma Disorder: Distinguishing, Diagnosing, and the DSM

How One Tenacious Task Force Worked to Separate Developmental Trauma Disorder from PTSD in DSM-5

Mary Sykes Wylie • November 21, 2013

In 2001, the Cummings Foundation convened a group of child psychiatrists, public policy experts, and representatives from the Department of Justice, Department of Health and Human Services, and Congressional staff to consider the deplorable state of services to traumatized children. This initiative led to the establishment of the Congressionally mandated National Child Traumatic Stress Network (NCTSN).

In order to study the symptomatology of the children seen within the NCTSN, Boston psychiatrist and trauma expert Bessel van der Kolk and his colleague Joseph Spinazzola organized a complex trauma task force. Between 2002 and 2003 they conducted a survey (via clinician reports) of 1,700 children receiving trauma-focused treatment and experiencing the effects of child abuse at 38 different centers across the country.

They found more evidence of what two decades of research had already revealed: Nearly 80% of the surveyed kids had been exposed to multiple and/or prolonged interpersonal trauma, and of those, fewer than 25% met the diagnostic criteria for Post-Traumatic Stress Disorder (PTSD).

Instead, these children showed pervasive, complex, often extreme, and sometimes contradictory patterns of emotional and physiological dysregulation. Their moods and feelings could be all over the place—rage, aggressiveness, deep sadness, fear, withdrawal, detachment and flatness, and dissociation—and when upset, they could neither calm themselves down nor describe what they were feeling.

In 2005, the complex trauma task force—chaired by van der Kolk—began working in earnest on constructing a new diagnosis, called Developmental Trauma Disorder, which, they hoped, would capture the multifaceted reality experienced by chronically abused children and adolescents.

In January 2009, they submitted to the Diagnostic and Statistical Manual (DSM) Trauma, PTSD, and Dissociative Disorders Subwork Group an elaborate criteria set (DSM-speak for symptom list) for Developmental Trauma Disorder: Exposure to prolonged trauma, causing pervasive impairments of psychobiological dysregulation (of emotions and bodily functions, of awareness and sensations, of attention and behavior, of their sense of self and their relationships), as well as at least two symptoms of standard PTSD, and multiple functional impairments (with school, family, peer group, the law, health, and jobs or job training).

According to van der Kolk, the DSM committee responded that the complex trauma task force had “inundated” them with too much data about Developmental Trauma Disorder, but not the right kind: They needed to submit other kinds of data concerning 17 issues, including possible genetic transmission, environmental risk factors, temperamental antecedents, bio-markers, familial patterns, treatment response, and so on.

The DSM subcommittee, chaired by Matthew Friedman, executive director of the National Center for PTSD, wrote that “the consensus is that is it unlikely that Developmental Trauma Disorder can be included in the main part of DSM-5 in its present form because of the current lack of evidence in support of the diagnosis and the lack of prospective testing of your proposed diagnostic criteria.”

The complex trauma task force argued that this was a proposed diagnosis, which didn’t officially exist yet, and so—in that great Catch-22 tradition of DSM—couldn’t qualify for the funding for the kind of research the DSM subcommittee wanted to see. But their argument was still unconvincing.

Though temporarily stymied, the NCTSN task force is by no means defeated. They’ve been able to raise the money for a Developmental Trauma Disorder field trial and enlisted the sites that are able to carry out the required research.

“We’re still going ahead full throttle,” says van der Kolk. “I feel very optimistic.”

~ Discover what it takes to get a new diagnosis recognized by the Diagnostic and Statistical Manual. Download The Puzzle of Trauma: Redefining PTSD in the DSM for FREE!