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| |  Researchers Propose a Simpler Definition for Major Depressive Disorder Providence, RI -- July 23, 2009 -- Researchers have proposed that the definition for major depressive disorder (MDD) should be shortened to include only the mood and cognitive symptoms that have been part of the definition in the Diagnostic and Statistical Manual of Mental Disorders (DSM) for the past 35 years, excluding those symptoms that are currently part of the definition that may be associated with medical illness rather than depression. The proposal is based on a study that appears in the July 23 online first edition of the journal Psychological Medicine. The current definition of MDD in the fourth edition of the DSM (DSM-IV) includes 9 symptoms -- a definition that has remained essentially unchanged since the 1970s. With preparations for the fifth edition of the DSM underway, researchers have proposed that there are 2 practical problems with the symptom criteria: the length of the definition and the difficulty in applying some of the criteria to patients with comorbid medical illnesses. Lead author Mark Zimmerman, MD, Outpatient Psychiatry, Rhode Island Hospital, and The Warren Alpert Medical School of Brown University Rhode Island, Providence, Rhode Island, said, “While the principles guiding criteria revision have not been clearly explained, we believe that existing diagnostic criteria should be revised when a conceptual problem is identified, or a more valid or simpler method of defining a disorder is developed. The reason for even considering a change to the symptom criteria for major depressive disorder after all these years is 2-fold.” “First, studies have indicated that there are significant gaps in the knowledge or application of the MDD criteria among practitioners. Second, somatic criteria that are currently part of the DSM-IV definition such as fatigue or sleep or appetite disturbances are also symptoms of other medical illnesses and may not be indicative of a major depressive episode.” The proposal recommends a shortened list of symptom criteria that includes only low mood, loss of interest or pleasure, guilt/worthlessness, impaired concentration/indecision, and suicidal thoughts. It would exclude the somatic criteria of fatigue, appetite disturbance, and sleep disturbance, as these may be associated with medical illnesses other than depression. Their proposal is called the “simpler definition of MDD.” Using the Structured Clinical Interview for DSM-IV (SCID), the researchers conducted a study of more than 2,500 patients. The patient population consisted of 1,100 psychiatric outpatients, 210 pathological gamblers who presented for treatment, and 1,200 candidates for bariatric surgery. Across all patients, the level of agreement between the simplified definition and the DSM-IV definition was more than 95%. “After eliminating the 4 somatic criteria from the DSM-IV definition of MDD, leaving the 5 mood and cognitive features, a high level of concordance was found between this simpler definition of MDD with the original classification in all 3 patient samples studied.” Dr. Zimmerman added, “This new definition offers 2 advantages over the DSM-IV definition: it is briefer and therefore more likely to be recalled and correctly applied in clinical practice, and it is free of somatic symptoms, thereby making it easier to apply with medically ill patients.” The researchers noted that there are implications to changing the criteria for MDD. Because their findings indicated that the simpler definition is highly concordant with the current version, there would be no meaningful impact on prevalence rates. Reducing the number of criteria, however, would reduce the time needed to fully assess criteria in patients and diagnostic interviews could be shortened. Dr. Zimmerman concluded, “In deciding how to proceed in the next version of the DSM, the conceptual and practical advantages of a briefer set of criteria that is easy to apply to all patients, particularly medically ill patients, needs to be weighted against the disadvantages of deviation from tradition.” SOURCE: Lifespan
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