Neuropsychological performance of patients with soft bipolar spectrum disorders

Authors

  • Kangguang Lin,

    1. Laboratory of Neuropsychology, The University of Hong Kong, Hong Kong
    2. Department of Psychiatry, Guangzhou Psychiatric Hospital, Affiliated Hospital of Guangzhou Medical University, Guangzhou
    3. Laboratory of Cognitive Affective Neuroscience, The University of Hong Kong
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  • Guiyun Xu,

    1. Department of Psychiatry, Guangzhou Psychiatric Hospital, Affiliated Hospital of Guangzhou Medical University, Guangzhou
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  • Weicong Lu,

    1. Department of Psychiatry, Guangzhou Psychiatric Hospital, Affiliated Hospital of Guangzhou Medical University, Guangzhou
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  • Huiyi Ouyang,

    1. Department of Psychiatry, Guangzhou Psychiatric Hospital, Affiliated Hospital of Guangzhou Medical University, Guangzhou
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  • Yamei Dang,

    1. Department of Psychiatry, Guangzhou Psychiatric Hospital, Affiliated Hospital of Guangzhou Medical University, Guangzhou
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  • Yangbo Guo,

    1. Department of Psychiatry, Guangzhou Psychiatric Hospital, Affiliated Hospital of Guangzhou Medical University, Guangzhou
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  • Kwok-Fai So,

    1. The State Key Laboratory of Brain and Cognitive Sciences, The University of Hong Kong, Hong Kong
    2. GMH Institute of CNS Regeneration, Jinan University, Guangzhou
    3. Department of Ophthalmology, The University of Hong Kong, Hong Kong
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  • Tatia MC Lee

    Corresponding author
    1. Laboratory of Neuropsychology, The University of Hong Kong, Hong Kong
    2. Laboratory of Cognitive Affective Neuroscience, The University of Hong Kong
    3. The State Key Laboratory of Brain and Cognitive Sciences, The University of Hong Kong, Hong Kong
    4. Institute of Clinical Neuropsychology, The University of Hong Kong, Hong Kong, China
    • Corresponding author:

      Guiyun Xu, M.D.

      Department of Psychiatry

      Guangzhou Psychiatric Hospital

      Affiliated Hospital of Guangzhou Medical University

      36 MingxinLoad, Guangzhou

      Guangdong Province 510370

      China

      Fax: 86-020-81891391

      E-mail: xuguiyun290@hotmail.com

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  • Kangguang Lin and Tatia M.C. Lee contributed equally to this work.

Abstract

Objectives

There is much evidence that shows that a substantial number of individuals with DSM-IV-defined unipolar depression (UP) manifest hypomanic sub-syndrome and bipolar diathesis. Other definitions have conceptualized the term soft bipolar spectrum (SBP) for these individuals. Little is known about the cognitive profiles of individuals with SBP. We hypothesized that they are representative of individuals with bipolar II disorder and are different from that of ‘strict’ UP.

Methods

Consecutive referrals suffering major depressive episodes were categorically assigned to groups of either bipolar I disorder (n = 98), bipolar II disorder (n = 138), or UP (n = 300). Based on the SBP criteria by Akiskal and Pinto (17), patients with UP were subdivided into 81 SBP and 219 strict UP. We administered self- and clinician-administered scales to evaluate affective temperaments, and neuropsychological tests to assess seven cognitive domains.

Results

Patients with SBP performed significantly better than strict UP patients in the domains of processing speed (p = 0.002), visual-spatial memory (p = 0.017), and verbal working memory (p = 0.017). Compared to patients with bipolar I disorder, patients with SBP were significantly better in set shifting (p < 0.001) and visual-spatial memory (p = 0.042). Patients with SBP performed similarly to patients with bipolar II disorder in all of the cognitive domains tested (p > 0.05). There was a group × cognitive domain interaction effect between bipolar I disorder, bipolar II disorder, SBP, and strict UP groups [Pillai's = 2.231, df = (18,1437), p = 0.002].

Conclusions

Our data suggest that patients with SBP differ from patients with UP not only in external validators (e.g., family history of bipolar disorder) and hypomanic symptoms, but also in neuropsychological performance and that the profiles of cognitive functioning were different across bipolar I disorder and ‘bipolar II spectrum’ that subsumes bipolar II disorder and SBP.

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