Research report
Contrasting chronic with episodic depression: An analysis of distorted socio-emotional information processing in chronic depression

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Abstract

Background

The specific features that differentiate chronic and episodic depression are widely unknown. This study compares the chronic and episodic form of depression with regard to two domains of socio-emotional information processing: Decoding of other people's emotional states (Theory of Mind) and the perception of own emotions (alexithymia).

Method

This study compares 30 chronically and 29 episodically depressed patients by tapping into Theory of Mind deficits with a multi-method approach and by assessing alexithymic deficits. Furthermore, a retrospective assessment of adverse relational childhood experiences is administered.

Results

The observed results reveal distorted information processing in only one of the two domains: Chronically depressed patients scored higher in alexithymia than episodically depressed patients, while no group differences in the domain of Theory of Mind were found. Moreover, alexithymia was found to mediate the influence of adverse relational childhood experiences on depression type (chronic vs. episodic).

Limitations

Due to the reliance on retrospective and self-report data, results should be interpreted with due caution. In addition, the cross-sectional design limits causal conclusions.

Conclusions

These results suggest a potentially central role of the deficient perception of own emotions in causing or maintaining chronic depression. Derived practical implications include a focus on the perception of own emotions in the psychotherapy of chronic depression. If future research continues to uncover systematic differences in the psychopathology of chronic and episodic depression, chronicity should be more strongly considered when classifying unipolar depressive disorders.

Introduction

Chronic depression is defined as depressed mood for the duration of two years or more (e.g., Klein, 2008). Recently, the interest in chronic depression has grown for good reasons. It is estimated that as much as 20% of all instances of depression become chronic (Gilmer et al., 2005, Keller and Hanks, 1994, Kessler et al., 1994). Furthermore, treatment response rates are below the rates for nonchronic depression (Howland, 1991, Thase et al., 1994) and chronic depression has a heavy impact on individuals' social-vocational adjustment and functioning (Evans et al., 1996, Gilmer et al., 2005). However, surprisingly little is known about specific differences between chronic and non-chronic depression. Such knowledge is needed as it will ultimately contribute to therapeutic methods that specifically tackle chronic states of depression. In trying to fill this gap, the current study makes three contributions to the literature on chronic depression. First, we take a perspective that simultaneously considers deficits in the perception of others' and own emotions. Thereby, we go beyond previous research that focused exclusively on the interpersonal aspect of socio-emotional information processing (cf. Wilbertz et al., 2010, Zobel et al., 2010). Second, by analyzing the processes possibly underlying chronic depression we aim to contribute to the knowledge on causing and/or maintaining factors. In our analyses, we connect patients' potential deficits in socio-emotional information processing with their classification into chronic and episodic depression. Third, by carving out systematic differences between chronically and episodically depressed patients, we lend support to the view that chronic depression may be a useful and meaningful diagnostic category.

In the 4th edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV; American Psychiatric Association, 1994) chronically depressed individuals are grouped in one of two diagnostic categories: Major depressive disorder or dysthymic disorder (i.e., a chronic but mild depressive condition). Patients are classified with respect to the severity of depressive symptoms, while the diagnoses of chronic and episodic major depression are collapsed into a single diagnostic category. Empirical evidence, however, suggests that chronic major depression and dysthymic disorder are more alike than the chronic and episodic form of major depression with respect to familial liability, psychosocial-functioning, comorbidity rates, and treatment response rate (Gilmer et al., 2005, Klein et al., 2004). It has been argued that the classificatory distinction between chronic and nonchronic depression – combined with an index of severity – may be more useful and meaningful than the distinction between dysthymic disorder and major depressive disorder (Klein, 2008). To corroborate or disprove this view, studies that identify and assess potential differences in the etiology and pathology of chronic and episodic states of depression are needed.

Existing comparisons of chronic and episodic depression that focus on childhood experiences revealed that the chronic group has experienced poorer familial relationship quality and more emotional neglect (Brown and Moran, 1994, Klein et al., 2009, Lizardi et al., 1995) as well as more sexual and physical abuse (Brown and Moran, 1994, Zlotnick et al., 1997). Concerning demographic and illness-related variables it was shown that chronically depressed patients have an earlier onset of disorder (e.g., Gilmer et al., 2005), are less often married, have less social support (Brown et al., 2008, Evans et al., 1996), and suffer from greater functional impairments than episodically depressed patients (Evans et al., 1996, Gilmer et al., 2005). Strikingly, little is known about systematic differences in the pathology and, more specifically, about differences in pathology-related information processing between chronic and episodic depression. The available evidence is limited to evidence that chronically depressed patients have higher somatic comorbidity (Angst et al., 2009) and psychiatric comorbidity, especially social phobia (Angst et al., 2009, Riso et al., 2002). Moreover, chronically as compared to episodically depressed individuals express greater suicidality (e.g., Gilmer et al., 2005). Constantino et al. (2008) finally showed that chronically depressed patients endorse a more hostile-submissive interpersonal style than episodically depressed patients.

In this research, we propose in line with McCullough's theoretical account of chronic depression (McCullough, 2000, McCullough, 2003) that chronically depressed patients exhibit distortions in socio-emotional information processing. According to McCullough, adverse relational childhood experiences cause a deficient socio-emotional development. Affected individuals do not sufficiently attend to the emotional states of others, they are disconnected from social feedback, and they endorse an egocentric world view characterized by a lack of perspective taking and empathy. Put differently, chronically depressed individuals are assumed to have poor abilities related to Theory of Mind (henceforth ToM; Lee et al., 2005). ToM is conceived as a set of abilities that develop through childhood and enable humans to understand other peoples' mental states and intentions (Premack and Woodruff, 1978).

As empirical tests of McCullough's theoretical views, two recent studies investigated ToM-related deficits in chronic depression (Wilbertz et al., 2010, Zobel et al., 2010). However, these studies yielded contradicting findings: Zobel et al. observed lower performances of chronically depressed patients compared to healthy controls, while Wilbertz et al. failed to demonstrate these deficits. Importantly, chronically depressed participants were compared with healthy controls in both studies. The hypothesis of distorted socio-emotional information processing of chronically as compared to episodically depressed patients (McCullough, 2003) has not been subject of empirical testing yet. In our view, the inclusion of an episodically depressed group as the baseline group is most informative for the investigation of chronic depression because thereby the impact of current depressive symptoms is controlled for and emerging differences can be unambiguously attributed to the chronicity aspect of depression.

As chronically depressed individuals are hypothesized to exhibit an overt lack of perspective taking and empathy (cf. McCullough, 2003), it seems warranted to go beyond pure ability assessments and extend the research focus to motivational aspects of ToM. In this respect, Wilbertz et al. (2010) suggested that not only the ability but also the motivation to decode socio-emotional information and respond to it might be diminished in chronic depression. To address this call, this study applies a multi-method approach: An ability test is combined with a test of spontaneous interpersonal behavior and self-report measures of everyday behavior.

Socio-emotional information processing is, however, not limited to an interpersonal perspective. Previous research revealed a close association of the ability to perceive others' emotions and own emotions in healthy people (Joseph and Newman, 2010, Wong and Law, 2002) and both abilities together can be considered the foundation of successful social functioning (cf. Joseph and Newman, 2010). The current research thus goes beyond a focus on others' emotions and additionally investigates differences between chronically and episodically depressed patients with respect to recognizing and understanding own emotions. A related syndrome of deficient recognition of own emotions has been termed “alexithymia” (Sifneos, 1973). Alexithymia is defined as difficulties in describing and identifying feelings as well as externally oriented thinking rather than reflection on inner experience (Nemiah et al., 1976). Two sets of empirical findings make alexithymia a relevant concept in the study of chronic depression. First, aversive relational childhood experiences seem to be characteristic for both conditions, chronic depression and alexithymic deficits (for a review, see Thorberg et al., 2011). Second, alexithymic deficits were shown to lead to similar interpersonal problems as in chronic depression (Constantino et al., 2008), that is a cold and distant interpersonal style (Spitzer et al., 2005, Vanheule et al., 2010) as well as low relationship quality and low social support (Hesse and Floyd, 2011, Humphreys et al., 2009). Recent research even suggested that alexithymic deficits directly link childhood maltreatment to depression (Thomas et al., 2011).

The aim of the current study is threefold. First, we compare chronically and episodically depressed patients on tasks that assess (a) emotion decoding in others (the ability component of ToM) and (b) responding with respect to the other person's perspective (the motivation component of ToM). Chronic and episodic depression have not yet been compared in view of these measures. Second, abnormalities of chronically depressed individuals in decoding and labeling their own emotional experiences are assessed (alexithymia). Finally, in a preliminary causal analysis (i.e., a mediation analysis) we investigate whether observed socio-emotional deficits (i.e., decoding others' and/or own emotions) are predictive of the patients' classification into the two categories of chronic and episodic depression. Following our reasoning that chronic depression is a consequence of deficient socio-emotional development (cf. McCullough, 2003), we expect that the influence of adverse childhood experiences on the diagnostic classification is mediated by deficient socio-emotional information processing.

Section snippets

Participants and procedure

30 inpatients with chronic depression (50% female) and 29 inpatients with episodic depression (44.8% female) took part in this study. Participants were recruited from the EOS-Clinic for Psychotherapy in Münster, Germany. The diagnosis of potential participants was assessed with the SKID (Wittchen et al., 1997) and an adapted version of the LIFE-Interview, which focuses on the aspect of chronicity (Keller et al., 1987). All clinical interviews were performed by a trained clinical psychologist.

ToM abilities and perspective taking behavior

Self-reported perspective taking was analyzed by a t-test. There was no difference between chronically depressed (3.30 ± 0.71) and episodically depressed participants (3.31 ± 0.67), t(57) < 0.3, ns.

The ToM performance task (reading-the-mind-in-the-eyes task; RME) was analyzed by a Multivariate Analysis of Variance (MANOVA). The group variable (chronic vs. episodic depression) was entered as the independent variable. As dependent measures, the total performance score of the RME as well as the separate

Discussion

This research presents an informative comparison of chronically and episodically depressed participants. Though the interest in chronic depression has risen notably in the last years, there is a lack of studies contrasting these two forms of depression directly. Chronically and episodically depressed participants in our study did not differ in a performance test of mental states decoding (i.e., ToM abilities). Paralleling our findings on ToM abilities, we also did not find group differences in

Role of funding source

There was no involvement of a funding source.

Conflict of interest

All authors declare to have no conflict of interest.

Acknowledgment

We would like to thank all patients who took part in this study for their cooperativeness and patience. Furthermore, thanks are due to all colleagues of the EOS-Clinic for supporting our work in various ways.

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