Refining the diagnostic criteria for major depression on the basis of empirical evidence

The operational diagnostic criteria for major depression have remained more or less the same in the past 40 years, but this does not mean that they are uncontroversial. Indeed, the DSMIV construct of major depression has been criticized for being too inclusive and heterogeneous, thus encompassing several homeostatic reactions to adverse life events, and marginalizing possibly valid categorical entities such as melancholia and psychotic depression, which may have significant biological correlates and treatment implications. Furthermore, the DSMIV duration and impairment criteria have been never validated, and the requested minimum number of depressive symptoms does not have an acceptable empirical support (1). In view of all this, Gordon Parker s proposal for a re-definition of clinical depression, aimed to distinguish it from normative mood states and to better characterize its melancholic and psychotic subtypes, is of great interest. However, a problem with this proposal is that its empirical basis is not convincingly described. For instance, while the inclusion in the definition of clinical depression of symptoms such as hopeless and helpless and distinctively amotivated is supported by the evidence that they outperform several of current DSM-IV depressive symptoms in their ability to differentiate major depression from non-major depression (2), the same cannot be said for symptoms such as like giving up and asocial (in mixing less with other people) , which appear either not clearly formulated or unlikely to have an acceptable specificity. Furthermore, the author s attempt to address the issue of lack of cleavage between major depression and melancholia is understandable, but excluding from the definition of clinical depression symptoms such as psychomotor retardation, loss of energy and diminished ability to concentrate appears problematic, and may affect the discrimination between that condition and normative mood states. Also debatable is the exclusion of neurovegetative symptoms such as insomnia and loss of appetite, whose predictive relationship with clinical validators which are different from those associated with cognitive symptoms of depression has been recently documented (3). On the other hand, the author s attempt to operationalize in more objective terms the impairment criterion appears timely, since that criterion, in its current formulation, depends toomuch on the clinician s and the patient s subjective judgment, and is so generic to be actually redundant (4). The author places psychotic depression at the highest level of his hierarchical model, requiring this subtype to be diagnosed only when the criteria for melancholia are also met. This, however, is in contrast with recent evidence from epidemiological and clinical studies suggesting that psychotic depression does not need to be severe (it may either mild or moderate ) (5). Indeed, the DSM-5 is going to separate the psychosis specifier from the severity dimension. In conclusion, Parker s proposal adds significantly to the current debate on the validity of the operational diagnostic criteria for major depression. However, the fact that current criteria for that condition have remained unmodified for several decades, representing the basis for a variety of assessment instruments and being used for several epidemiological studies, calls for a thorough assessment of the available research evidence before any drastic change is implemented. This assessment is being done as part of the process of revision of the DSM-IV and ICD-10, and the author s proposal is unlikely to be considered if its empirical support is not clearly delineated.