Research report
Subtyping depression in the medically ill by cluster analysis

https://doi.org/10.1016/j.jad.2011.03.004Get rights and content

Abstract

Background

There is increasing awareness of the need of subtyping major depressive disorder, particularly in the setting of medical disease. The aim of this investigation was to use both DSM-IV comorbidity and the Diagnostic Criteria for Psychosomatic Research (DCPR) for characterizing depression in the medically ill.

Methods

1700 patients were recruited from 8 medical centers in the Italian Health System and 1560 agreed to participate. They all underwent a cross-sectional assessment with DSM-IV and DCPR structured interviews. 198 patients (12.7%) received a diagnosis of major depressive disorder. Data were submitted to cluster analysis.

Results

Two clusters were identified: depressed somatizers and irritable/anxious depression. The somatizer cluster included 58.6% of the cases and was characterized by DCPR somatization syndromes (persistent somatization, functional somatic symptoms secondary to a psychiatric disorder, conversion symptoms, and anniversary reactions) and DCPR alexithymia. The anxious/irritable cluster had 41.4% of the total sample and included DCPR irritable mood and type A behavior and DSM-IV anxiety disorders.

Limitations

The study has limitations due to its cross-sectional nature. Further, these findings require additional validation in another sample.

Conclusions

The findings indicate the need of expanding clinical assessment in the medically ill to include the various manifestations of somatization, irritable mood, type A behavior and alexithymia, as encompassed by the DCPR. Subtyping major depressive disorder may yield improved targets for psychosomatic research and treatment trials.

Introduction

Major depressive disorder has emerged as an extremely important source of comorbidity in medical disorders (Katon, 2003). It was found to affect quality of life and social functioning, to lead to increased health care utilization, to be associated with higher mortality (particularly in the elderly people), to have an impact on compliance and to increase susceptibility to medical illness (DiMatteo et al., 2000, Fava and Sonino, 1996, Frasure-Smith and Lespérance, 2003, Katon, 2003, Schulz et al., 2002).

There is increasing awareness of the fact that diagnosis of major depressive disorder is too broad and of the need of subtyping it for selecting the right treatment for each individual patient (Baumeister and Parker, 2010, Bech, 2010, Lichtenberg and Belmaker, 2010). This particularly applies to depression in the setting of medical disease. The category adjustment disorder with depressive mood is commonly used but has not attracted adequate research and offers little to our understanding (Semprini et al., 2010). The majority of patients with major depressive disorder do not qualify for one, but for several Axis I and Axis II disorders (Zimmerman et al., 2002). A source of subtyping may lie in this comorbidity. Feinstein, however, when he introduced the concept of comorbidity, referred to any “additional co-existing ailment” separate from the primary disease, even in the case this secondary phenomenon does not qualify as a disease per se (Feinstein, 1970). Indeed, in clinical medicine the many methods that are available for measuring comorbidity are not limited to disease entities (de Groot et al., 2003). Current emphasis in psychiatry is about assessment of symptoms resulting in syndromes identified by diagnostic criteria (DSM). However, there is emerging awareness that also psychological symptoms that do not reach the threshold of a psychiatric disorder may affect quality of life and entail pathophysiological and therapeutic implications (Fava et al., in press). The Diagnostic Criteria for Psychosomatic Research (DCPR) were developed by an international group of investigators to translate the large body of evidence accumulated in psychosomatic medicine in operational tools (Porcelli and Rafanelli, 2010, Porcelli and Sonino, 2007, Wise, 2009). The DCPR allow to translate clinically illness behavior (the ways in which individuals experience, perceive, evaluate and respond to their health status), the various modalities of somatization and constructs such as demoralization, irritable mood and alexithymia (Porcelli and Sonino, 2007, Wise, 2009, Porcelli and Rafanelli, 2010, Cockram et al., 2009, Fava and Sonino, 2009). Whenever the DCPR have been used in conjunction with the DSM, they have been found to carry additional clinical information (Porcelli and Rafanelli, 2010).

The aim of this investigation was to use both DSM and DCPR for examining the feasibility of subtyping in a highly heterogeneous group of medical patients diagnosed as suffering from a major depressive disorder by a cluster analysis technique.

Section snippets

Design, procedures and subjects

Patients were recruited from different medical settings in an ongoing multicenter project concerned with the psychosocial dimensions of medical patients (Porcelli and Sonino, 2007). Although studies involved in the research project had different aims and sample sizes, they shared a common methodology in the assessment of psychopathology and psychosocial syndromes. Patients were recruited consecutively, with the intent of being representative of their respective patient populations:

  • 1.

    Consecutive

Results

A total of 198 patients (12.7%; 62.6% female) received a diagnosis of Major Depressive Disorder (MDD) according to DSM-IV criteria, with a mean age of 45.79 (SD = 14.39) years, and a mean of 9.73 (SD = 3.99) years of education. Of these, fifty-one (25.8%) had at least 1 comorbid Axis I disorder (particularly, anxiety disorders), and 185 (93.4%) presented at least 1 comorbid DCPR syndrome (mainly demoralization, somatization syndromes, and irritability). Frequencies for each of the diagnostic

Discussion

This study has indicated that major depressive disorder in the medically ill may be classified into two clusters.

The first cluster (named somatizer) encompassed about 60% of cases and was characterized by DCPR somatization syndromes (persistent somatization, functional somatic symptoms secondary to a psychiatric disorder, conversion symptoms, and anniversary reactions) and alexithymia. The DCPR category of persistent somatization is conceptualized as a grouping of functional symptoms involving

Role of funding source

This study was supported in part by a grant from Compagnia di San Paolo, Torino, Italy to Dr. Rafanelli. Compagnia di San Paolo had no further role in the study design; in the collection, analysis and interpretation of data; in the writing of the report; and in the decision to submit the paper for publication.

Conflict of interest

Drs. Guidi, Fava, Picardi, Porcelli, Grandi, Grassi, Pasquini, Quartesan, Rafanelli, Rigatelli, and Sonino have no conflict of interest to declare. Dr Bellomo has been sponsored as speaker at meetings and congresses by Ely-Lilly, Janssen-Cilag, AstraZeneca, Bristol Meyers Squibb, Lundbeck, Pfeizer, and Glaxo-SmithKline in the previous year.

Acknowledgement

Nothing to report.

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