Elsevier

Journal of Affective Disorders

Volume 82, Issue 3, 1 November 2004, Pages 403-409
Journal of Affective Disorders

Research report
Deficiency of theory of mind in patients with remitted mood disorder

https://doi.org/10.1016/j.jad.2004.04.004Get rights and content

Abstract

Background: Recent researches on theory of mind (ToM) in patients with mood disorders have revealed deficits of ToM ability during episodes. In this study, we aimed to test ToM ability among patients with unipolar or bipolar depression currently in remission. Methods: ToM ability and IQ obtained by Wechsler Adult Intelligence Scale-Revised (WAIS-R) were evaluated in 50 patients with remitted depression, who met the criteria of mood disorders of DSM-IV, and 50 matched healthy controls. Results: The patients with mood disorders showed statistically significant impairment in a second-order false question (Fisher's Exact Test p<0.0001). No significant difference was shown in the other three areas of ToM between the patients and the controls. In addition, no correlation of the four areas of ToM with IQ obtained by WAIS-R was found. Limitations: The relation of ToM deficit to other specific cognitive impairment was not examined. Conclusions: Our results suggest that depressive patients in symptomatic remission have a lower ability of second-order false belief. The ToM impairment suggests a decline of skillful social relationships. Evaluation of ToM ability in depressive patients in remission may be useful to provide treatment for better social adjustment.

Introduction

“Theory of mind” (ToM) is a term used by Premack and Woodruff (1978) in their first report, “Does the chimpanzee have a theory of mind?”. The authors defined ToM as the attribution of mental states and the prediction of other people's behavior on the basis of their mental state (e.g., purpose, intention, belief, inference, and inherence), i.e., self-consciousness. According to Brüne (2003) however, the term is more often used to refer to the theory of other minds, hence it should be defined as the ability to infer others' mental states and predict their behavior (Brüne, 2003). It is thought that ToM relates to attribution theory (Premack and Woodruff, 1978).

Because, Perner and Wimmer (1985) asserted that the understanding of others' “false beliefs” means explicit representation of the minds of other people than oneself, a “false belief question” depends on whether one understands that “person A ‘incorrectly’ believes that object X exists in location Y.” This is a “first-order false belief” Baron-Cohen et al., 1999, Perner and Wimmer, 1985. On the other hand, a “second-order false belief” is that “person B ‘incorrectly’ believes that person A thinks that object X exists in location Y.” The ability of human beings to understand such relationships forms one's self-consciousness as perceived from the point of view of others, develops representation N-order beliefs, and is essential cognition in the complex human social system.

The consensus view has been that primates predict the behavior of others using ‘mind reading’ by implicitly holding ToM to accomplish one's own social success. This ability is called “social intelligence” Brüne, 2001, Byrne, 1995, Dunbar, 1998.

The brain regions involved in social intelligence are called the “social brain”. The main parts of it involve the orbitofrontal cortex, superior temporal gyrus, and the amygdala Baron-Cohen et al., 2000, Brothers, 1990, Brüne, 2001, Dunbar, 1998. Using fMRI and PET, brain imaging studies of subjects performing ToM tasks have directly shown participation of the prefrontal cortex (PFC) Rusell et al., 2000, Fletcher et al., 1995.

ToM, which originated from evolutional and developmental psychology, may have important consequences of possibly elucidating psychopathology. Baron-Cohen et al. (1985) provided evidence for a ToM deficit in autistic children, possibly accounting for their inability to pretend and communication disturbance, using a well-known experiment, “Sally and Ann”. The ToM deficit hypothesis has also been applied to schizophrenia (Brüne, 2001).

There have been very few reports discussing the correlation between mood disorders and ToM. In previous reports on the disability of ToM in schizophrenia, only small numbers of patients with mood disorders were included in the control groups Frith and Corcoran, 1996, Drury et al., 1998, Sarfati et al., 1999, Fletcher et al., 1995, Mazza et al., 2001. Moreover, those reports contain ambiguity in the methods of examination. Accordingly, there is no consensus of results on cognitive deficit in mood disorders. Kerr et al. (2003) found that ToM deficits were observed in patients with bipolar affective disorder in the acute phase.

It is important to clarify whether impairment of ToM ability is influenced by affective symptoms or not. We thus performed a ToM task (picture sequence task, first-order false belief question, second-order false belief question, reality question, and tactical deception question) in 50 patients with mood disorders and 50 controls. The patients were studied when they were in remission from depressive episodes in order to avoid the influence of depressive symptoms on the test results. We also investigated the correlation of ToM ability with IQ, linguistic IQ, and clinical characteristics.

Section snippets

Subjects

The subjects were 50 patients (28 male and 22 female) who met the DSM-IV criteria for mood disorder (American Psychiatric Association, 1994), and whose last episode was major depression but were in remission. We evaluated the severity of depression of the subjects using the Hamilton Rating Scale for Depression (HAM-D; Hamilton, 1960). A score of seven or lower was defined as remission. All patients were in remission for more than 1 month. Thirty-four patients had unipolar disorder and 16 had

Results

The age and sex of the subjects in the M- and C-groups are shown in Table 1. No difference was shown in age, sex, or IQ between the two groups. In the M-group, the mean age at the onset of mood disorder was 39.13±9.18 years (mean±S.D., range 14 to 62), and the mean duration of illness was 5.4±5.5 years (range 0.2 to 22.0). The duration of illness was defined as the period from the onset of the first episode to the time of evaluation, both for unipolar and bipolar disorders. The mean score of

Discussion

A previous study demonstrated ToM deficits in symptomatic bipolar patients (Kerr et al., 2003) just as reported in schizophrenia. In this study, ToM ability, particularly second-order false belief, among patients during remission was impaired in both unipolar and bipolar disorders. The ToM results showed no correlation with IQ, age, sex, or duration of illness in either unipolar disorder or bipolar disorder. The main implication of this finding is that although patients seem recovered from

Acknowledgements

We are deeply indebted to Dr. M. Brüne for providing the ToM test battery. We also acknowledge Prof. K. Dairoku, Musashi Women's University, for his guidance concerning ToM tasks and intelligence, and Prof. J. Hasegawa and Prof. A. Senju, University of Tokyo, for their advice on evolutional psychology. We are also deeply indebted to Drs. M. Shinohara, T. Tamaoki, H. Iguchi, H. Hirakuri, T. Hirata, R. Kuroki, and K. Yasuda for their support. We would like to thank Ms. T. Tezuka of University

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