The DSM-5 definition of mental disorder

In his paper ‘DSM-5: Ordering disorder?’ Malhi (2013) rightly stresses that the definition of mental disorder is crucial in assessing psychiatric symptoms, and that defining mental disorder is extraordinarily difficult. In my view, “the clinical significance question”, as formulated in DSM-III and DSM-IV, is one of the many hard to solve conceptual problems one has to address in defining mental disorder. Interestingly enough, even though the deficiencies of this criterion largely outnumber its usefulness it is more likely than not that it will stay in DSM-5 as one of the essential features of the definition of a mental disorder.

The goal of introducing the notion of clinical significance to the DSM-III definition of mental disorder was to raise the threshold. The idea was that if clinically significant distress and functional impairment of a particular individual is adduced as one of the key criteria of his/her mental disorder, then healthy people are less likely to be diagnosed as mentally disordered.

The introduction of the clinical significance criterion proved mostly unsuccessful. Spitzer, chair of the Task Force of DSM-III, in a paper he wrote along with Wakefield (1999), admits that the wholesale application of clinical significance criterion is “problematic and has no empirical support”. Kendell (2002) describes the introduction of “clinical significance” in the definition of generic mental disorder as a “cumbersome strategy that has proved only partially successful in eliminating false positives”, and Aragona (2009) remarks that “clinical significance cannot be a solution in the search of a demarcation criterion”.

It is noteworthy that Pincus (1998), vice-chair of the Task Force of DSM-IV, received a letter from Spitzer, in which he asks whether colleagues from the American Psychiatric Association were pleased that the criterion “clinically significant” was added to the operational definition of many disorders. “The answer was both yes and no. We are not satisfied”, writes Pincus, “because, in fact the criterion is imprecise and not easily measured in a standard way.” And Pincus adds: “Nonetheless, overall, we are pleased with the decision because it places decision-making in the hands of the individual clinician.”

Not surprisingly, the introduction of the clinical significance criterion did not serve its purpose. First, there is no operational definition of clinically significant symptoms and syndromes for that matter. Consequently it is anyone’s guess what a clinically significant symptom (syndrome) means. Second, since the clinically significant criterion is, in fact, a dimensional criterion, the question arises as to who is expected to decide where the breaking point is placed (up to which distress and functional impairment is insignificant): those who have introduced this questionable criterion, or each and every clinician? And on the basis of which elements might a clinician be able to make such a decision? Third, a mental disorder is by definition a clinically significant syndrome; so are its basic components: distress and impairment. Thus, it is redundant to say that a mental disorder is a “clinically significant behavioural or psychological syndrome or pattern that occurs in an individual” (American Psychiatric Association, 1994). A clinically insignificant behavioural or psychological syndrome or pattern, that is, a clinically insignificant mental disorder, would be a contradiction in terms.

Given the foregoing, one can only speculate as to why the clinical significance criterion has been preserved in the DSM-5 proposal for the definition of mental/psychiatric disorder by Stein et al. (2010), as well as in First and Wakefield’s (2010) suggested revisions to the Stein et al. proposed definition of mental disorder. The following explication provided by Stein et al. for keeping the clinical significance criterion is unfounded, not to mention misleading: “Given that we do not have objective biomarkers that adequately define most mental/psychiatric disorders, the clinical significance criterion remains useful in differentiating disorder from normality.”

Among the proposed revisions under discussion by the DSM-5 Task Force is a revised definition of a mental disorder that in May 2012 (American Psychiatric Association, 2012) was presented as the most recent proposal by members of the Task Force. I am not aware of a more recent proposal than this one. In it, a mental disorder is defined as “a health condition characterized by significant dysfunction in an individual’s cognitions, emotions, or behaviour that reflects a disturbance in the psychological, biological, or developmental process underlying mental functioning. Some disorders may not be diagnosable until they have caused clinically significant distress or impairment of performance.”

The authors of the definition stop short of saying how serious a dysfunction should be to be perceived as significant, and how much someone’s cognitions, emotions, or behaviour should be impaired/dysfunctional to be clinically significant, that is, to be instrumental in diagnosing a particular individual as mentally disordered.

Furthermore, it is Regier himself (2004), the DSM-5 Task Force vice-chair, who asserted that “despite the prominence of clinical significance in diagnostic criteria, there is currently no consensus as to how it should be defined or operationalized.”

As for the definition of a mental disorder, there is no answer to the clinical significance question. It will stay as one of those dilemmas that make the definition of a mental disorder seemingly intractable.

See Debate by Malhi, 2013, 47(1): 7–9.