Date Published: January 23, 2017
Publisher: Public Library of Science
Author(s): Lucas Primo de Carvalho Alves, Marcelo Pio de Almeida Fleck, Aline Boni, Neusa Sica da Rocha, Kent E. Vrana.
Melancholic features of depression (MFD) seem to be a unidimensional group of signs and symptoms. However, little importance has been given to the evaluation of what features are related to a more severe disorder. That is, what are the MFD that appear only in the most depressed patients. We aim to demonstrate how each MFD is related to the severity of the major depressive disorder.
We evaluated both the Hamilton depression rating scale (HDRS-17) and its 6-item melancholic subscale (HAM-D6) in 291 depressed inpatients using Rasch analysis, which computes the severity of each MFD. Overall measures of model fit were mean (±SD) of items and persons residual = 0 (±1); low χ2 value; p>0.01.
For the HDRS-17 model fit, mean (±SD) of item residuals = 0.35 (±1.4); mean (±SD) of person residuals = -0.15 (±1.09); χ2 = 309.74; p<0.00001. For the HAM-D6 model fit, mean (±SD) of item residuals = 0.5 (±0.86); mean (±SD) of person residuals = 0.15 (±0.91); χ2 = 56.13; p = 0.196. MFD ordered by crescent severity were depressed mood, work and activities, somatic symptoms, psychic anxiety, guilt feelings, and psychomotor retardation. Depressed mood is less severe, while guilt feelings and psychomotor retardation are more severe MFD in a psychiatric hospitalization. Understanding depression as a continuum of symptoms can improve the understanding of the disorder and may improve its perspective of treatment.
Major depressive disorder (MDD) is one of the most frequent psychiatric disorders both in the community and in psychiatric settings . The World Health Organization presented a report in 2011 estimating that depressive disorders were the second leading cause of years lived with disability . However, several studies show that MDD is a very heterogeneous syndrome [3–6] that is characterized by many different presentations and possibly with different risk factors for its individual symptoms [7,8]. Actually, MDD DSM-V  are quite similar to DSM-III criteria released in 1980 ; there are only minor changes regarding bereavement . Nonetheless, most experts agree that DSM criteria have been chosen through consensus instead of empirical research . Oostergaard et al (2011) showed that 1,492 different presentations of the same syndrome according the DSM-IV criteria  are mathematically possible . Therefore, a particular problem is created when we consider some disorders categorical, while evidence favors a dimensional approach for them; MDD is a major example . Symptoms listed in DSM-V for MDD criteria seem to have a Gaussian distribution in the general population , suggesting that it may be a diagnostic convention imposed on a continuum of depressive symptoms . Nevertheless, although there is still no quantitative laboratory measures for the diagnosis and evaluation of severity of MDD, levels of impairment have long been successfully represented in quantitative scales .
We included a sample of 291 individuals with diagnosis of MDD. Demographic characteristics of the sample are shown in Table 1. For the HDRS-17, only one subject had 1 missing value, and so they were excluded from the analysis. This did not happen to HAM-D6, because the missing value was on item 5 of the HDRS-17 (intermediate insomnia), which is not part of the HAM-D6. So, the subject was re-included in the analysis of HAM-D6.
The present study has three main findings. The first one is that the 6 melancholic features of HAM-D6 are well distributed across the continuum of severity of MDD in hospitalized patients. This means that they are able to differentiate both the less and the most severe patients in this setting. The items psychomotor retardation and guilt feelings are in the top level of severity, followed by psychic anxiety, somatic symptoms and work and activities in the middle, and depressed mood at the bottom level. The second one is that, HDRS-17 does not fit to the unidimensional Rasch model and may not represent a continuum of symptoms that get worse whereas the syndrome becomes more severe, as also previously showed by Bech . Finally, the third major finding is replication of Bech’s original study , showing that a group of 6 symptoms extracted from the HDRS-17 (HAM-D6) represents an unidimensional construct that clinically represents melancholic depression in hospitalized patients.