Do personality traits predict first onset in depressive and bipolar disorder? MAJ VINBERG CHRISTENSEN, LARS VEDEL KESSING Christensen MV, Kessing LV. Do personality traits predict first onset in depressive and bipolar disorder? Nord J Psychiatry 2006;60:79  /88. Oslo. ISSN 0803-9488. The aim was to investigate whether personality traits predict onset of the first depressive or manic episode (the vulnerability hypothesis) and whether personality might be altered by the mood disorder (the scar hypothesis). A systematic review of population-based and high-risk studies concerning personality traits and affective disorder in adults was conducted. Nine cross-sectional high-risk studies, seven longitudinal high-risk studies and nine longitudinal population-based studies were found. Most studies support the vulnerability hypothesis and there is evidence that neuroticism is a premorbid risk factor for developing depressive disorder. The evidence for the scar hypothesis is sparse, but the studies with the strongest design showed evidence for both hypotheses. Only few studies of bipolar disorder were found and the association between personality traits and bipolar disorder is unclear. Neuroticism seem to be a risk factor by which vulnerable individuals can be identified, thus preventing the development of depressive disorder. A connection between personality traits and development of bipolar disorder, and evidence of a personality-changing effect of affective episodes need to be further investigated.  Affective disorders, Depressive disorder, Follow-up studies, Personality, Prospective studies. Maj Vinberg Christensen, Rigshospitalet, afsnit 6234, Blegdamsvej 9, DK-2100 Copenhagen, Denmark, E-mail: Maj.Vinberg@rh.dk; Accepted 22 December 2004. I dentifying risk factors in depressive and bipolar disorder (in the following named affective disorder) would allow for putative prevention and early treatment. Personality traits may predict first onset and recurrence of episodes. Specific character traits may cause vulner- ability to affective episodes and have been proposed to play a causal role in the development of affective disorder: the vulnerability hypothesis (1, 2). Otherwise, the affective disorder itself may affect personality, therefore the experience of sustained mood disturbance may cause personality changes (3) leading to personality deviance as a scar effect: the scar hypothesis (or complication hypothesis). The scar effect may depend on the number of episodes, the severity of the depression and the response to treatment (4). In 1921, Kraepelin suggested that there was a depressive temperament or personality characterized by a ‘‘permanent gloomy emotional stress in all the experiences of life’’ and a cyclothymic temperament preceding manic-depressive illness (5), and there seems to be a close relation between premorbid personality traits and differential psychopathology (6). What comes first, the trait or the affective disorder? This is a problem for clinicians. A trait may be defined as ‘‘a co-variant set of behavioural acts; it appears thus an organizing principle which is deduced from the observed generality of human behaviour’’ (7). Personality is composed of a relatively stable set of traits, and traits are not directly observable; they are inferred (8). In particular, neuroticism and introversion have been suggested to cause a higher incidence of depression; neuroticism refers to emotional instability, vulnerability to stress and a proneness to anxiety (7) detected by the items anxiety, guilt, dependence, hypochondria, unhap- piness, inferiority and obsessiveness (8). The relation between affective disorder and person- ality traits is complicated (9) and most studies investi- gate personality traits after the patients have experienced one or more affective episodes (e.g. 10,11). The possibi- lity that the personality changes follow mood disorders cannot be excluded: therefore, retrospective studies are not able to distinguish between premorbid personality patterns and personality patterns resulting from epi- sodes of the illness (12). Prospective studies, measuring personality traits be- fore the onset of affective disorder and following successive episodes, provide the most valid information on the relationship between personality traits and affective disorder (1, 13). This relationship can be examined in two ways: 1) by following psychological # 2006 Taylor & Francis DOI: 10.1080/08039480600600300