Research report Differences in neuroticism and extraversion between patients with bipolar I or II and general population subjects or major depressive disorder patients Pekka Jylhä a,b , Outi Mantere a,b , Tarja Melartin a , Kirsi Suominen a,b , Maria Vuorilehto a , Petri Arvilommi a,b , Sami Leppämäki c , Hanna Valtonen a,b , Heikki Rytsälä a , Erkki Isometsä a,c, ⁎ a Department of Mental Health and Substance Use, National Institute of Health and Welfare, Helsinki, Finland b Department of Psychiatry, Jorvi Hospital, Helsinki University Central Hospital, Espoo, Finland c Department of Psychiatry, Helsinki University Central Hospital, Helsinki, Finland article info abstract Article history: Received 9 December 2009 Received in revised form 25 January 2010 Accepted 25 January 2010 Available online 19 February 2010 Background: Whether levels of neuroticism or extraversion differ between patients with bipolar disorder (BD), major depressive disorder (MDD) and subjects from the general population, or between BD I and BD II patients, remains unclear. Methods: BD patients (n = 191) from the Jorvi Bipolar Study, and MDD patients (n = 358) from both the Vantaa Depression Study and the Vantaa Primary Care Depression Study cohorts, were interviewed at baseline and at 18 months. A general population comparison group (n = 347) was surveyed by mail. BD patients’ neuroticism and extraversion scores, measured by Eysenck Personality Inventory, were compared at an index interview, when the levels of depression and mania were lowest, with scores of MDD patients and general population controls. Comparisons were also made between BD I (n = 99) and BD II (n = 92) patients. Results: In multinomial logistic regression, BD patients had higher neuroticism (OR = 1.17, p b 0.001) and lower extraversion (OR = 0.92, p = 0.003) than the general population. When entered simultaneously into the model, the effect of extraversion disappeared. In logistic regression, the levels of neuroticism and extraversion did not differ between BD and MDD patients, or between BD I and II patients. Limitations: Patients’ personality scores were not pre-morbid. Conclusions: Levels of neuroticism and extraversion are unlikely to differ between BD and MDD patients, or between BD I and II patients. The overall level of neuroticism is moderately higher and extraversion somewhat lower in BD patients than in the general population. High neuroticism may be an indicator of vulnerability to both bipolar and unipolar mood disorders. © 2010 Elsevier B.V. All rights reserved. Keywords: Bipolar disorder major depressive disorder general population neuroticism extraversion personality 1. Introduction The relationship between personality and bipolar disorder (BD) is complex. Personality features may result from, predispose an individual to, or modify the clinical picture of an affective illness, or be an attenuated expression of affective disorder (Goodwin and Jamison, 2007). Two personality dimensions, neuroticism and extraversion, have been found to be global personality traits (Pervin et al., 2005). Neuroticism is characterized by proneness to anxiety, emotional instability, and self-consciousness, whereas extraversion involves positive emotionality, energy, and dominance (Pervin et al., 2005). Both neuroticism and extraversion are to some degree inherited traits (Pervin et al., 2005). High neuroticism has been shown to be a risk factor or indicator for major depressive disorder (MDD) in prospective epidemiological twin (Kendler et al., 1993, 2006), general population (Ormel et al., 2004a), and clinical (Boyce et al., 1991; Clayton et al., 1994; Hirschfeld et al., 1989; Nyström and Journal of Affective Disorders 125 (2010) 42–52 ⁎ Corresponding author. Professor of Psychiatry, Department of Psychiatry, Institute of Clinical Medicine, University of Helsinki, P.O. Box 22, FI-00014 Helsinki, Finland. Fax: +358 9 47163735. E-mail address: erkki.isometsa@hus.fi (E. Isometsä). 0165-0327/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.jad.2010.01.068 Contents lists available at ScienceDirect Journal of Affective Disorders journal homepage: www.elsevier.com/locate/jad