Research report The distinct temperament profiles of bipolar I, bipolar II and unipolar patients ☆ Hagop S. Akiskal a,b,c, ⁎ , Nael Kilzieh d , Jack D. Maser a,b,c , Paula J. Clayton a,e , Pamela J. Schettler b , M. Traci Shea a , Jean Endicott a , William Scheftner a , Robert M.A. Hirschfeld a , Martin B. Keller a a National Institute of Mental Health Collaborative Program on the Psychobiology of Depression, Clinical Studies, USA b University of California at San Diego, CA, USA c Veterans Administration Hospital, San Diego, CA, USA d Veterans Administration Hospital, Tacoma, WA, USA e American Foundation for Suicide Prevention, New York, NY, USA Abstract Background: Despite a plethora of studies, controversies abound on whether the long-term traits of unipolar and bipolar patients could be differentiated by temperament and whether these traits, in turn, could be distinguished from subthreshold affective symptomatology. Methods: 98 bipolar I (BP-I), 64 bipolar II (BP-II), and 251 unipolar major depressive disorder (UP-MDD) patients all when recovered from discrete affective episodes) and 617 relatives, spouses or acquaintances without lifetime RDC diagnoses (the comparison group, CG) were administered a battery of 17 self-rated personality scales chosen for theoretical relevance to mood disorders. Subsamples of each of the four groups also received the General Behavior Inventory (GBI). Results: Of the 436 personality items, 103 that significantly distinguished the three patient groups were subjected to principal components analysis, yielding four factors which reflect the temperamental dimensions of “Mood Lability”, “Energy- Assertiveness,”“Sensitivity–Brooding,” and “Social Anxiety.” Most BP-I described themselves as near normal in emotional stability and extroversion; BP-II emerged as labile in mood, energetic and assertive, yet sensitive and brooding; MDD were socially timid, sensitive and brooding. Gender and age did not have marked influence on these overall profiles. Within the MDD group, those with baseline dysthymia were the most pathological (i.e., high in neuroticism, insecurity and introversion). Selected GBI items measuring hypomania and biphasic mood changes were endorsed significantly more often by BP-II. Finally, it is relevant to highlight a methodologic finding about the precision these derived temperament factors brought to the UP–BP differentiation. Unlike BP-I who were low on neuroticism, both BP-II and UP scored high on this measure: yet, in the case of BP-II high neuroticism was largely due to mood lability, in UP it reflected subdepressive traits. Limitation: We used self-rated personality measures, a possible limitation generic to the paper-and-pencil personality literature. It is therefore likely that BP-I may have over-rated their “sanguinity”; or should one consider such self-report as a reliable reflection of one's temperament? One can raise similar unanswerable questions about “depressiveness” and “mood lability.” Journal of Affective Disorders 92 (2006) 19 – 33 www.elsevier.com/locate/jad ☆ When these analyses were first undertaken in 1994, Dr. Akiskal was at the office of the Director at the National Institute of Mental Health, Rockville, MD, Dr. Maser with the Mood, Anxiety and Personality Disorders Branch at the same Institute, and Dr. Kilzieh at Washington University, St. Louis, Dr. Clayton at the University of Minneapolis, Minnesota, and Dr. Schettler with Datamax, Rockville, MD; Donald Vena provided database development and statistical programming. ⁎ Corresponding author. V.A. Psychiatry Service (116-A), 3350 La Jolla Village Drive, San Diego, California 92161, USA. Tel.: +1 858 552 8585x2226; fax: +1 858 534 8598. E-mail address: hakiskal@ucsd.edu (H.S. Akiskal). 0165-0327/$ - see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.jad.2005.12.033