Fallacious reasoning in the argument to eliminate the major depression bereavement exclusion in DSM-5.

We thank E. Corruble and R. Pies for their comments on our review of the evidence pertaining to the validity of the DSM’s major depression (MDD) bereavement exclusion (BE) 1. Regarding the former letter, as our review explained, Corruble’s studies 2,3,4 provide no evidence regarding the BE’s validity, because the BE was misapplied. This conclusion is not “dogmatic”, but based on Corruble’s data. After interviewing depressed patients, physicians in Corruble’s studies marked each MDD symptom and criterion “yes” or “no” on a questionnaire. Criterion E (the BE) for MDD requires that, if the depressive episode occurs during bereavement, it must have one or more of certain features that are uncharacteristic of normal grief (i.e., psychomotor retardation, feelings of worthlessness, suicidal ideation, marked impairment, psychotic ideation, or duration greater than 2 months) showing that it is better explained as MDD than as normal bereavement. Thus, a “yes” rating on criterion E indicated that the episode was a bona fide case of MDD, whereas a “no” rating meant that the episode was placed in Corruble’s “excluded” sample. However, the vast majority of physicians who checked “no” to criterion E also checked “yes” to either “psychomotor retardation” (70.6%), “suicidal ideation” (36.0%), or “feelings of worthlessness” (66.8%). Yet, criterion E requires that these symptoms not be present for a case to be excluded, so the “no” rating for criterion E was logically inconsistent with the “yes” on the symptom ratings. If the BE had been applied correctly, these symptoms’ rates would necessarily have been 0% among the excluded cases. In essence, the symptom profile served as a validity check on the physicians’ application of the BE, and revealed its invalidity. We speculated that lack of training contributed to the physicians’ incorrect application of the BE. Corruble objects that the physicians did receive some preparation. The fact that they still got confused suggests that the BE’s double-negative wording requires simplification, and we proposed such a simplification in our review. But this does not change the fact that the physicians applied the BE incorrectly. Corruble suggests that there are two possible explanations for the contradictory results – either the physicians incorrectly applied the BE, or the BE is so complex that it cannot be correctly applied in real world settings. However, both these “explanations” imply that criterion E was not applied correctly, supporting our conclusion. Attempting to elevate her physicians’ errors into a general condemnation of the BE, Corruble asserts the BE is so complex that it is incapable of real-world application. However, although confusingly worded, the BE ultimately relies on duration, impairment, and symptom criteria – the same kind found in most DSM diagnostic criteria sets. Physicians who initially misapply the BE generally learn to apply it correctly with further training, and lay interviewers have applied the BE successfully in research studies. Moreover, physicians have a similar trajectory in learning to diagnose depression in general, with more incorrect than correct diagnoses initially, so the BE’s diagnostic learning curve is not unique 5. Corruble’s publications misleadingly suggest that her studies reveal the surprising severity of BE-excluded episodes, rather than explaining that her “excluded” sample would not be excluded by the BE. For example, in her letter, Corruble states that “our results… show that the bereavement exclusion criterion has a poor discriminant validity…”. However, the results show nothing about the BE’s discriminant validity, because the criterion was not properly applied. Recent recurrence studies described in our review strongly support the BE’s discriminant validity. Corruble asks elsewhere “Should the E criterion for the diagnosis of MDE be retained?... Or should it be deleted?” and answers “Unfortunately, our data cannot answer these questions” 6. Our review explains why we strongly agree with this conclusion. Regarding Pies’ letter, he argued in recent papers that the available evidence supports the invalidity of the BE 7,8. Our review shows that the evidence Pies cited offers no such support. Pies now claims that no evidence is needed to eliminate the BE, because there was no adequate evidence for having included it in the first place. However, the procedures established for revising the DSM sensibly require that changes be justified by evidence 9. If one generally adopted Pies’ proposed standard for the BE that there must be methodologically perfect studies to justify retention of a criterion, then much of the DSM would have to be thrown out along with the BE. Yet in many cases, including the BE, there are good reasons anchored in medical observation and relevant but less-than-perfect evidence allowing a plausible judgment of a condition’s likely status, pending further evidence. Pies’ own standard when arguing for eliminating the BE was the “best available evidence” or the “preponderance of evidence” despite “the limited data we have” 7,8. Pies summarily dismisses Clayton’s 10,11 pre-DSM-III prospective studies of grief as justification for the BE’s introduction. However, whatever their limitations, those studies provided crucial and still-persuasive evidence that some MDD symptoms are also common in normal grief, and that the BE is necessary to avoid massive false positives. Recent studies confirm Clayton’s early conclusions (see below). Pies claims that “the burden of proof should fall on those who believe the bereavement exclusion should be retained”. Although this claim is questionable for the reasons above, nonetheless this burden has been met. As our review explained, two recent studies using different samples and follow-up periods reached convergent conclusions – that having a BE-excluded episode does not elevate the probability of recurrence of depression over background rates, whereas other types of MDD have recurrence rates much greater than population levels 12,13. Pies’ rejection of such evidence from epidemiological studies ignores the many well-known reasons why such studies offer superior scientific evidence and form the foundation for many DSM validity evaluations. Pies’ rejection of epidemiological evidence also rings hollow because he cited primarily epidemiological studies or reviews that relied on them when he argued for the BE’s elimination 7,8. Pies’ main argument against the BE has been that there is no evidence that BE-excluded episodes are “fundamentally different”, “less severe or persistent”, have different “prognostic or treatment implications”, or “significantly differ… in terms of symptom picture, risk of recurrence, or clinical outcome” from other MDD 7,8. All of these assertions are contradicted by the recent recurrence evidence. Pies asserts that it is a “rudimentary matter of logic” that bereaved individuals meeting MDD criteria should be considered disordered, unless there is evidence that they differ importantly from other MDD cases. This is not in fact a logically valid principle (such an inference is warranted only if you have first established the essential homogeneity of the overall syndrome, something that has not been done for any DSM-defined syndrome, let alone MDE), but no matter. The recurrence studies 12,13 provide precisely the demanded evidence of important differences. By Pies’ own stated standards, the evidence supports the retention of the BE.