Potential implications of the harmful dysfunction analysis for the development of DSM-V and ICD-11

Now that the development of both DSM-V and ICD-11 is underway, we should consider the potential practical implications of Wakefield's harmful dysfunction analysis for the revisions of these classifications. A research agenda for DSM-V (1) was published in 2002 with the goal of stimulating "research and discussion in the field in preparation for the eventual start of the DSMV revision process" (2) and included a chapter on "Basic nomenclature issues for DSM-V". Among its recommendations were suggestions that DSM-V include a "definition of mental disorder that can be used as a criterion for assessing potential candidates for inclusion in the classification", noting that the definition of mental disorder included in DSM-IV is not "cast in a way that allows it to be used as a criterion for deciding what is and is not a mental disorder", largely because "the definition fails to define or explain the crucial term dysfunction" (3). One of the strengths of Wakefield's harmful dysfunction analysis is that it helps to elucidate the key concept of "dysfunction", which Wakefield refers to as the "factual" component of the definition of mental disorder. Wakefield defines dysfunction as the failure of some brain or psychological mechanism to perform its naturally designed function. Although our current superficial understanding of mental processes limits our ability to precisely discern the various naturally designed functions of the brain, this approach is conceptually very appealing, because, as Wakefield points out in his many examples, it conforms to our common sense notions of what is and what is not a mental disorder.

If past experience is any guide, the upcoming revisions of the DSM and ICD classifications will bring with them many proposals for adding new disorders (4). While some proposals might entail carving out a new disorder from an existing category (for example, the proposal to add bipolar II disorder to DSM-IV involved reclassifying cases that would have been diagnosed as major depressive disorder in DSM-III-R) and thus primarily involve the boundary with other mental disorders, many proposals involve new diagnostic entities that impact the boundary with normality. It is this latter group for which Wakefield's harmful dysfunction analysis will be most relevant for insuring that the diagnostic entities are defined in such a way as to meet the criteria for a mental disorder. The harmful dysfunction analysis stresses that any definition of mental disorder should include elements that indicate both the presence of a dysfunction (i.e., the failure of a naturally designed mechanism) and a significant negative impact related to that dysfunction in terms of distress or impairment.

Previous efforts to construct criteria sets have primarily focused on the "harm" component by either including lists of symptoms that are, especially in aggregate, inherently harmful in terms of causing the individual distress or impairment (e.g., recurrent panic attacks, phobic avoidance) or else including a clinical significance criterion that explicitly requires impairment or distress (e.g., "the symptoms cause clinically significant distress or impairment in social, occupational, or other important areas of functioning"). Much less commonly are criteria included that address the "dysfunction" component of the definition, i.e., criteria that clarify that the harmful symptoms are the result of a failure in the individual of some designed function as opposed to resulting from non-disorder-related causes, like inadequate educational or financial opportunities, relational conflicts, etc. Most often, criteria are added that exclude specific situations in which the harmful symptoms are clearly caused by something that does not represent a failure of a designed function. For example, the diagnostic criteria for selective mutism specifically exclude situations in which the failure to speak is due to a lack of knowledge of, or comfort with, the spoken language required in the social situation. Rarely, the failed mechanism is explicitly included in the definition of a disorder; for example, stuttering is defined as a "disturbance in the normal fluency and time patterning of speech [that is] inappropriate for the individual's age" (5).

To illustrate how the harmful dysfunction analysis might apply in the consideration of proposals to include new disorders in DSM-V or ICD-11, take for example compulsive sexual behavior disorder (6), which is likely to be proposed for inclusion in DSM-V and ICD-11. Given that there are certainly at least some cases of individuals whose lives have been ruined by an inability to control their sexual impulses, the issue is not whether compulsive sexual behaviour can ever be considered a disorder, but instead how to tailor the criteria set for compulsive sexual behaviour disorder so that it falls within the definition of mental disorder. Using the harmful dysfunction analysis as a guide, the definition would have to include clear parameters indicating the harm caused by the symptoms as well as an explicit indication of the nature of the dysfunction, in this case, an internal failure to keep sexual impulses under control. To further clarify the internal nature of the dysfunction, additional criteria might be added to exclude other non-disordered causes for high levels of sexual activity (e.g., naturally high libido, situations in which outlets for sexual impulses are otherwise severely restricted).

It should be noted that, as Wakefield has pointed out elsewhere (7,8), the analysis outlined above has never been methodically applied to the current DSM-IV criteria sets, leading to many potential false positives that stem from not excluding cases in which symptoms arise from a non-disordered cause. Thus, the aforementioned harmful dysfunction analysis should not just be applied in the construction of criteria sets for new disorders, but should be used to guide revisions of the existing criteria sets as well.