A group of researchers proposes the definition for major depressive disorder (MDD) should be shortened to include only mood and cognitive symptoms.
If accepted, the 35-year-old definition found in the Diagnostic and Statistical Manual of Mental Disorders (DSM) would not include symptoms that are associated with medical illness.
The proposal is based on a study that appears in the online first edition of the journal Psychological Medicine.
The current definition of major depressive disorder includes nine symptoms — a definition that has remained essentially unchanged since the 1970s.
As preparations for a new edition of the DSM are underway, the researchers state that there are two practical problems with the symptom criteria: the length of the definition and the difficulty in applying some of the criteria to patients who have an additional mental illness.
The researchers’ 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 remove fatigue, appetite disturbance and sleep disturbance (increased sleep or insomnia) as these may be associated with medical illnesses other than depression. Their proposal is called the “simpler definition of MDD.”
Lead author Mark Zimmerman, MD, director of outpatient psychiatry at Rhode Island Hospital, says, “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 two-fold.”
Zimmerman, who is also an associate professor of psychiatry and human behavior at The Warren Alpert Medical School of Brown University, continues, “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.”