Open Access Open Badges Research article

Brain structural changes and neuropsychological impairments in male polydipsic schizophrenia

Tomohisa Nagashima1*, Makoto Inoue12, Soichiro Kitamura1, Kuniaki Kiuchi1, Jun Kosaka13, Koji Okada1, Naoko Kishimoto1, Toshiaki Taoka4, Kimihiko Kichikawa4 and Toshifumi Kishimoto1

Author Affiliations

1 Department of Psychiatry, Nara Medical University, Kashihara, Nara, Japan

2 National Hospital Organization Yamato Mental Medical Center, Yamatokoriyama, Nara, Japan

3 Sakai City Mental Health Center, Sakai, Osaka, Japan

4 Department of Radiology, Nara Medical University, Kashihara, Nara, Japan

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BMC Psychiatry 2012, 12:210  doi:10.1186/1471-244X-12-210

Published: 26 November 2012



Polydipsia frequently occurs in schizophrenia patients. The excessive water loading in polydipsia occasionally induces a hyponatremic state and leads to water intoxication. Whether polydipsia in schizophrenic patients correlates with neuropsychological impairments or structural brain changes is not clear and remains controversial.


Eight polydipsic schizophrenia patients, eight nonpolydipsic schizophrenia patients, and eight healthy controls were recruited. All subjects underwent magnetic resonance imaging (MRI) and neuropsychological testing. Structural abnormalities were analyzed using a voxel-based morphometry (VBM) approach, and patients’ neuropsychological function was assessed using the Brief Assessment of Cognition in Schizophrenia, Japanese version (BACS-J).


No significant differences were found between the two patient groups with respect to the clinical characteristics. Compared with healthy controls, polydipsic patients showed widespread brain volume reduction and neuropsychological impairment. Furthermore, the left insula was significantly reduced in polydipsic patients compared with nonpolydipsic patients. These nonpolydipsic patients performed intermediate to the other two groups in the neuropsychological function test.


It is possible that polydipsia or the secondary hyponatremia might induce left insula volume reduction. Furthermore, this structural brain change may indirectly induce more severe neuropsychological impairments in polydipsic patients. Thus, we suggest that insula abnormalities might contribute to the pathophysiology of polydipsic patients.

Schizophrenia; Polydipsia; Volumetry; MRI; Neuropsychological impairment; Brief assessment of cognition in schizophrenia