Personality profile in depression has been discussed in different cultural and racial backgrounds by various explanatory models and is considered to be important in clinical practice. According to Kraepelin, the premorbid personality of depressive illness contains scrupulosity and patience. Boyce et al. developed the Interpersonal Sensitivity Measure (IPSM), finding hypersensitivity to interpersonal rejection as a personality feature in depression. Accumulating evidence suggests that introversion and neuroticism, assessed with the Eysenck Personality Inventory (EPI) and the NEO-Five Factor Inventory (NEO-FFI), are global personality features in depression.[3-5]
The psychobiological model of personality was proposed and the Temperament and Character Inventory (TCI) was developed by Cloninger et al. TCI is composed of four temperaments (novelty seeking [NS], harm avoidance [HA], reward dependence [RD], and persistence [PS]) and three characters (self-directedness [SD], cooperativeness [CO], and self-transcendence [ST]). Temperament refers to a heritable bias to basic stimulus-response and is considered to be related with different monoamine neurotransmitter functioning in the brain system, while character reflects cognitive processes and the self-concept, which develop during the lifespan. The TCI has been widely used in researches to examine personality aspects of psychiatric disorders, such as schizophrenia, bipolar disorder (BPD) as well as unipolar depression. Our group previously reported differences in personality profile between patients with unipolar major depressive disorder (MDD) and those with bipolar II, suggesting the possible use of TCI to discriminate between the two disorders. An important methodological issue is that personality profile assessed with a questionnaire is influenced by the state of the subject. Previous studies have consistently reported that patients with depression had higher HA scores than healthy controls;[11-14] however, high HA and low SD correlated with depression severity at the time of personality assessment.[10, 11, 13-17] In this context, TCI personality profile in depression could be explained by several proposed models, including trait-, state-effects, and scar model. The scar model is that personality features change as consequences of depression experience and remain in remitted patients. Another issue is the possible effects of ethnicity and its culture on the relation between personality and the development of depression. To our knowledge, there is only one study that compared TCI personality between patients with remitted MDD and healthy controls in Asian countries, indicating that only HA was significantly different and higher in the former than in the latter group.
Recurrence of depression is of great clinical importance. It is reported that 40–85% of depression is recurrent.[18, 19] Attempts have been made to predict recurrence in depressed patients from demographic, clinical and psychological factors. Some studies found age of onset and family history of psychopathology to be associated with recurrence.[20-22] Personality features might be linked with recurrence of depression. Indeed, high neuroticism measured by the Brief Revised Eysenck Personality Questionnaire was associated with recurrent episodes. To our knowledge, there is only one study that compared TCI personality between remitted depressed patients with single episode and those with recurrent episodes, reporting that the latter group demonstrated higher HA as compared with the former group.
The aims of the present study were twofold: to examine TCI personality profile in remitted MDD patients, minimizing the possible effects of current mood state, and to compare TCI personality between MDD patients with single episode (SGL-MDD) and those with recurrent episodes (REC-MDD) in order to elucidate personality profile associated with recurrence.
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The present study was conducted to compare personality in patients with remitted MDD and healthy controls as measured by TCI. All patients were in remission at the time of TCI assessment; therefore, the possible influence of mood and any other symptoms on TCI, which has been reported by previous researches,[12-15] could be minimized in the present study. Another aim of the current study was to examine the relation between TCI personality and recurrence of depression, comparing the remitted MDD patients with single episode and those with recurrent episodes. We found that there were significant differences in TCI personality dimension scores between the remitted patients with MDD and healthy controls, and between the remitted REC-MDD and SGL-MDD patients. Logistic regression analyses showed that HA and its subscore, fatigability (HA4), positively predicted REC-MDD.
An advantage of our study is that the sample size (n = 615 in total subjects, consisting of 86 patients and 529 healthy controls) was relatively large, compared to the precedent studies on TCI personality in remitted MDD patients (summarized in Table 4). In addition, total remitted MDD patients and control subjects were well matched for age, sex and education years, and these demographic variables and clinical characteristics, including depression severity, comorbidity and medication status, were also well matched for between the REC-MDD and SGL-MDD groups.
Patients with remitted MDD were found to have significantly higher HA and lower SD compared to healthy controls. As shown in Table 4, all directions of TCI results in patients as compared to controls were consistent with the previous studies.[12, 13, 16, 29] All previous studies except for the smallest study found higher HA in patients with remitted depression. Similarly, all but one found lower SD in remitted patients. Overall, our finding is consistent with these previous studies regardless of ethnic differences. Several studies have found that higher HA and/or lower SD in patients with current depression compared to controls remained even after patients achieved remission.[11, 12] A sib-pair study showed the high heritability of HA and SD, reporting that both depressed probands and their never-depressed siblings had higher HA and lower SD than controls. Furthermore, a prospective study showed that elevated levels of neuroticism assessed by the short form of the Brief Revised Eysenck Personality Questionnaire were predictive of future depressive episodes. The neuroticism is correlated with HA in TCI, which is reasonable as both personality traits reflect anxiety proneness and vulnerability to stressful situations. Taken together, our findings suggest that elevated HA and decreased SD may, at least in part, be trait markers associated with vulnerability to depression. However, our results may be explained in part by the scar model. A longitudinal study showed that neuroticism increased after experiencing an episode of depression, which provided evidence for the scar model, although the other longitudinal study failed to support it. There are few studies investigating TCI personality before, during and after the episode of depression. Further longitudinal prospective studies are warranted to elucidate state, trait or scarring effect on TCI personality in depression.
Many risk factors for the recurrence of depression, including not only clinical and biological factors but also psychosocial and psychological factors, have been reported. Accordingly, we hypothesized that there was an association between personality and recurrence. As compared to controls, TCI scores were significantly altered on two temperaments (low NS and high HA) and one character (low SD) in patients with REC-MDD and on one temperament (high HA) and one character (low SD) in those with SGL-MDD. Previous studies suggested that the combination of the two altered personalities, high HA and low SD, was specific to MDD,[14, 29] which was congruent with the present study. Early age of onset in chronic MDD was associated with recurrence.[20, 21] In addition, the high morbidity risk of depression in the relatives was associated with recurrent depression of probands.[20, 22] The logistic regression analyses with stepwise selection method to avoid multicollinearity showed that HA and its subscore, fatigability were found to be positively associated with REC-MDD as well as family history. The association between high HA and recurrence of depression is consistent with previous reports, while to our knowledge, this is the first report that found an association between high fatigability and recurrence of depression. A high score on fatigability means feeling fatigue easily and not feeling vigorous, which can be linked plausibly with the scar model, that is, the result of experience of recurrent depression. Taken together, although a prospective study is needed to assess the value of personality profile predicting recurrence of MDD, the statistically significant risk indicators for recurrence of depression that we found, HA and fatigability, can be useful to assess risk for recurrence of depression in patients with first-episode depression and may be related with the underlying vulnerability of recurrent depression. In clinical settings, physicians should follow first-episode patients longer if the patient has high HA and fatigability as well as family history of any psychiatric disease.
Recurrence of depression is related with bipolarity.[34, 35] Therefore, it is possible that symptoms of BPD would appear in the patients in life later on, especially in the REC-MDD group. In precedent studies, patients with BPD demonstrated higher HA score, compared to controls.[10, 36] However, there is no study in which TCI personality traits were compared between BPD and the subtypes of MDD, such as the REC-MDD. Further personality research might clarify the relation between BPD and recurrence of depression.
The mean age of onset was relatively high in this study population, compared to the previous epidemiologic study. It is reported that age of onset affected the comorbidity rate of personality disorder in depression, while a study by Celikel et al. found that age of onset did not correlate with TCI scales. To examine an influence of age of onset on the current results, we subdivided each of the REC-, and SGL-MDD groups into two subgroups using each mean age of onset as the cut-off point. There was no significant difference in HA score between the early-, and late-onset-REC-MDD groups or between the early-, and late-onset-SGL-MDD groups (data not shown). Although it cannot be entirely denied that late onset would influence the results of TCI in general, we would like to argue that at least the currently obtained difference between the REC- and SGL-MDD groups in HA score using age- and sex-matched samples, cannot solely be attributable to the relatively late age of onset.
The current study has several limitations. First, the sample size in the present study is not very large, which may cause type II errors. Second, the observed differences on TCI personality between the REC-MDD and SGL-MDD groups could be due to the effect of antidepressants. However, Gelfin et al. reported that antidepressant had no effect on personality characteristics, although findings have been inconsistent. Third, we chose the MDD patients with remission, regardless of the basal score of HDRS, that is, the initial severity of depression when they had been in a depressed state, which is reportedly a significant risk factor for non-remission. Therefore, the remitted MDD patients recruited in the current study might be biased in terms of initial severity of depression. Further studies with a larger sample of drug-free and clinically remitted MDD patients, using additional variables, such as initial severities of depression and anxiety, may be needed to extend and confirm the present results. Fourth, due to the cross-sectional nature of the study, we could not conclude any causal relation between TCI personality profile and MDD. In addition, family history data was not obtained by any structured interview. However, our results clearly suggested the association between recurrence of depression and family history of any psychiatric disorders. Lastly, the majority of the healthy controls were volunteers who participated in this research of their own accord, implying that sampling bias, favoring, for example, exploration or outgoing, could exist.
In conclusion, we obtained evidence for elevated HA and decreased SD in remitted MDD when compared to healthy controls in Japanese subjects. Dividing remitted MDD patients into two subgroups according to presence or absence of recurrence, there were differences in personality profile when compared with each other and with controls. Furthermore, HA and its subscore, fatigability, were found to be positively associated with REC-MDD. Our findings may contribute to elucidating the underlying vulnerability of recurrence of depression and to early intervention and prevention of recurrence of depression by clinically using high HA and fatigability as risk indicators.