Evaluating Stability and Change in Personality and Depression

Transcription

1 Journal of Personality and Social Psychology Copyright 1997 by the American Psychological Association, Inc. 1997, Vol. 73, No. 6, /97/$3.00 Evaluating Stability and Change in Personality and Depression Darcy A. Santor Dalhousie University R. Michael Bagby Clarke Institute of Psychiatry and University of Toronto Russell T. Joffe McMaster University Medical Centre Critics have argued that personality factors believed to represent a vulnerability to depression are not stable and are therefore state dependent. However, conclusions regarding the stability of personality and the relation between personality and depression have been drawn (a) without differentiating relative stability among individual differences from absolute stability of change scores and (b) without explicitly modeling change in personality as a function of change in depression. The relation between neuroticism and depression was examined in a sample of depressed outpatients (N = 71 ) receiving a 5-week trial of pharmacotherapy. Measures of neuroticism and extraversion demonstrated both relative stability and absolute change, and changes in neuroticism and extraversion scores were modestly or not at all accounted for by changes in depression scores. Claims that personality scores are not stable and are state dependent must be reconsidered. The relation between personality and depression is both complex and controversial. ~ Several models examining the relation between personality and depression have been proposed (for reviews, see Clark, Watson, & Mineka, 1994; Klein, Wonderlich, & Shea, 1993), and a number of different personality traits and characteristics have been examined (for a review, see Barnett & Gotlib, 1988), including both broad traits, such as neuroticism and extraversion, as well as specific vulnerability factors, such as dependency and self-criticism (Blatt, 1974) or sociotropy and autonomy (Beck, Epstein, Harrison, & Emery, 1983). One group of models suggests that personality traits can predispose individuals to depressive episodes (vulnerability model) or influence the course and expression of a depressive episode (pathoplasty and exacerbation models). A second group of models suggests that personality is largely incidental to the onset or course of depression. Personality is either a complication of a depressive episode (complication model) or the result of a third factor that is also responsible for the onset of a depressive episode (common cause model). In the first group of models personality can modify the onset, course, or expression of depression, whereas in the second group of models personality does not. These models are not exhaustive, nor are they mutually exclusive (cf. Clark et al., 1994; Klein et al., Darcy A. Santor, Department of Psychology, Dalhousie University, Halifax, Nova Scotia, Canada; R. Michael Bagby, Section on Personality and Psychiatry, Clarke Institute of Psychiatry, and Department of Psychiatry, University of Toronto, Toronto, Ontario, Canada; Russell T Joffe, McMaster University Medical Centre, Hamilton, Ontario, Canada. This research was funded by a senior research fellowship from the Ontario Mental Health Foundation. Correspondence concerning this article should be addressed to Darcy A. Santor, Department of Psychology, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4Jl. Electronic mail may be sent via the Internet to 1993). Moreover, evidence for each must be evaluated with respect to specific traits and vulnerability factors. Critics of personality models of depression have argued that there is little evidence for a stable vulnerability to depression. Elevated levels on personality traits like neuroticism may reflect the severity of depressive symptoms, but they do not exist independently of depressive symptoms (Barnett & Gotlib, 1988; Coyne & Gotlib, 1983). Support for this view comes from a large number of studies showing that scores on personality scales are either no different in remitted depressed patients than in nondepressed controls or are significantly lower in depressed patients tested in remission(for reviews, see Barnett & Gotlib, 1988; Segal & Ingram, 1995). Although a few studies have shown that personality traits like neuroticism (Schrader, 1994a; 1994b) and specific vulnerability factors like dependency and self-criticism (Bagby et al., 1994) do demonstrate stability over time, most studies favor the second group of models, namely those that posit that personality, by itself, is incidental to the onset and course of clinical depression. Some studies have shown that personality factors do predict the onset of depressive symptoms (Block, Gjerde, & Block, 1991 ) and depressive episodes (Kendler et al., 1993); however, many studies have not shown this (for a review, see Barnett & Gotlib, 1988). Because scores generally decrease following treatment interventions, critics have concluded that personality and vulnerability factors believed to constitute a vulnerability to depression are not stable, t Research has examined the relation between depression and broad personality traits, like neuroticism (Eysenck & Eysenck, 1985); cognitive vulnerability factors, like dependency and self-criticism (Blatt, 1974); as well as positive and negative dimensions of mood (Clark et al., 1994). Although there are important differences among these constructs, many of the issues raised by critics apply to these constructs equally. For purposes of clarity, we use the term personality to refer to all individual differences factors believed to constitute a vulnerability to depression, unless another meaning is specified explicitly. 1354

2 STABILITY AND CHANGE IN PERSONALITY AND DEPRESSION 1355 depend on levels of depressive severity, and cannot be used as markers of risk or vulnerability for depressive states (Haynes, 1992). A number of theorists have argued that broad personality dimensions like neuroticism and extraversion may influence the course and onset of depression (Akiskal, Hirshfeld, & Yerevanian, 1983; Hirshfeld & Klerman, 1979; Klein et al., 1993). Individuals disposed to experiencing subclinical negative affective states or to avoiding social interactions (Eysenck & Eysenck, 1985 ) are believed to be at greater risk for the onset of a depressive episode, a finding that some studies have supported although others have not (for a review, see Barnett & Gotlib, 1988). In addition to influencing the onset of a depressive disorder, personality factors like neuroticism and extraversion may also influence the course of the disorder (exacerbationpathoplasty models). For example, individuals more likely to experience negative moods may experience less benefit from positive activities and be more resistant to a change in mood, whereas individuals more likely to engage in social activities may be more likely to experience social activities as pleasurable. Demonstrating that personality factors like neuroticism and extraversion are stable in the context of acute change is crucial to models proposing that personality can influence the course and onset of depression. However, despite considerable research examining the stability of personality scores in the context of treating a depressive disorder, two important issues have not been adequately addressed. First, studies examining the stability of personality scores in the context of a treatment protocol for depression have focused almost exclusively on the absolute stability of scores rather than on the relative stability of scores. Absolute stability emphasizes the extent to which personality scores change over time, whereas relative stability emphasizes the degree to which the relative differences among individuals remain the same over time. Studies have not adequately examined the relative stability of personality traits in the context of acute change. If personality traits are to be viewed as potential moderators of processes involved in acute change, personality traits must demonstrate stability throughout the period of acute change. Second, studies examining absolute change on personality measures have not shown that changes in personality scores are directly related to changes in depression scores. No studies have explicitly evaluated the extent to which changes in absolute personality scores can be attributed to the changes observed in absolute levels of depressive severity. In the present study, we addressed two broad issues. First, we assessed the broader theoretical issue concerning the stability of personality in the context of change and distinguished relative stability from absolute stability. Second, we examined the more specific issues concerning the degree to which relative stability in personality may be accounted for by relative stability in depressive severity and how changes in personality are related to changes in depressive severity in a group of depressed outpatients receiving 5 weeks of pharmacotherapy. Distinguishing Absolute and Relative Stability Whether one accepts that personality traits are stable, enduring entities depends to a large degree on how stability is assessed. Clinical studies have typically examined the issue of stability in personality with the use of change scores over the course of a clinical trial. Numerous studies have been published that demonstrate that levels of neuroticism and depression decrease with the remission or amelioration of depressive symptoms (e.g., Bailey & Metcalfe, 1969; Duggan, Sham, Lee, & Murray, 1991; Hirschfeld, Klerman, Clayton, & Keller, 1983; Hirschfeld et al., 1983). However, clinical researchers have focused almost exclusively on the amount of absolute stability (or change) in individuals when drawing conclusions about the stability of personality and depression and generally expect far more absolute stability than anticipated by most contemporary personality researchers. Indeed, any significant change in personality scores accompanying changes in depression scores has generally been taken as evidence that personality is not stable, and attempts have rarely been made to distinguish absolute stability from relative stability. Only a few studies examining the relation between personality and depression have reported results bearing on both absolute and relative stability of personality measures (e.g., Coppen & Metcalfe, 1965; Duggan, Sham, Lee, & Murray, 1991 ); however, these studies have not examined the extent to which relative stability is related to levels of depressive severity over the period in which personality was assessed, nor have they assessed the degree to which change in personality is related to any observed change in depression. In contrast, personality researchers generally emphasize the degree of relative stability in personality scores assessed over long periods of time. Relative stability assesses the extent to which relative differences among individuals on measures of personality remain stable and is estimated through the use of measures of covariation, such as correlation coefficients. Large test-retest correlations indicate that relative differences among individuals are stable. Relative stability is essential to any notion of stability, a fact that clinical studies and critical reviews have generally ignored. On the basis of test-retest correlations, most contemporary personality researchers examining the longitudinal stability of personality traits have concluded that personality traits like neuroticism demonstrate considerable stability over time (Conley, 1985; Costa et al., 1986; Finn, 1986; Heady & Wearing, 1989). Test-retest correlations for traits like neuroticism and extraversion have been around.60 (Finn, 1986). Even when changes in absolute levels have been observed across time, effect sizes (to 2) have been extremely small and have been taken as evidence for stability rather than as evidence of change (Costa et al., 1986). Assessing the relative stability of personality measures in the context of acute change in depressive severity is important for a number of reasons. First, relative and absolute stability are conceptually distinct. Observing an absolute change in personality scores does not preclude the possibility that relative stability among personality scores can still be observed. Second, evidence regarding the relative stability of personality measures in the context of acute change, such as a treatment protocol specifically designed to effect change in depressive symptoms within short periods of time, is sparse. In fact, few studies have examined the relative stability of personality traits in the context of acute change, such as in a treatment protocol for depression. Most information regarding the relative stability of personality scores comes from longitudinal studies of personality in which little or no change in persons or situations is likely to be ob-

3 1356 SANTOR, BAGBY, AND JOFFE served. Personality researchers have generally studied individuals over long periods of time in populations that emphasize stability. For example, Heady and Wearing (1989) examined the stability of Neuroticism, Extraversion, and Openness to Experience in a final sample of 649 individuals assessed every 2 years over a 6-year period. Data were analyzed only for individuals who remained in the study for the entire 6 years, ignoring some 300 people lost to attrition. Yet it is precisely those people lost to attrition whose lives might be characterized as most unstable. In contrast, participants involved in treatment programs for depression can be characterized foremostly by a profound change in their lives, namely the onset of a major depressive disorder, and are likely to experience further change as a result of the treatment protocol. Consequently, many longitudinal studies may capitalize on a selection bias in favor of stability. Longitudinal studies of personality show high levels of stability in personality measures, but this has always been in a context in which little or no change in absolute levels of personality was observed (cf. Costa et al., 1986). As a result, it is less clear how relatively stable personality measures are in a context of acute change, such as a 5-week trial of pharmacotherapy for depression~ Third, evidence regarding the relative stability of personality measures in the context of change is essential in evaluating the appropriateness of other models of personality and depression that suggest that personality may influence the maintenance or course of a depressive episode (pathoplasty or exacerbation models). Evidence of relative stability in personality in the presence of absolute change in depressive severity allows researchers to begin asking why one individual shows many or few residual symptoms of depression at the end of treatment, is more or less resistant to change, or is more or less likely to relapse than another. Failure to find evidence for the relative stability of personality measures would preclude researchers from considering measures of personality as factors explaining symptomatic differences among individuals in the course or expression of a depressive disorder. Modeling Personality and Depression Critics of personality models examining the influence of personality on depression favor the view that personality is incidental to the etiology and course of a depressive episode. Both the relative stability of individual differences in personality and absolute changes in personality are attributed to levels of depressive severity or changes in depressive severity occurring during treatment. However, the extent to which both the relative stability and absolute stability of personality scores can be accounted for in terms of depression scores needs to be considered carefully. Although change in personality and depression has been widely demonstrated, the extent to which changes in personality can be accounted for by changes in depression is unclear. In fact, no studies have directly assessed the extent to which variance in change scores for personality can be accounted for by variance in change scores for depression. Trull and Goodwin (1993) examined the relation between change scores for measures of personality disorders and measures of depression. They demonstrated that changes in scores from inventories assessing personality disorders could not be accounted for in terms of changes in scores from depression inventories when assessed over a 6-month period. Both the relative stability of personality scores in the context of acute changes in depression and the extent to which changes in personality scores can be accounted for by changes in depressive severity are crucial to understanding the relation between personality and depression and the stability of personality traits in general. First, studying personality in the context of acute change provides important evidence regarding the conditions in which stability in personality may and may not be observed. Given the degree of change in mood that can be experienced over the course of treatment, the extent to which broad individual differences in personality dimensions such as neuroticism or negative affectivity, which assess the disposition to experience negative moods, remain stable or change is unclear. Second, ascertaining the degree to which personality measures show relative stability in the context of acute change is essential to models of personality that propose that personality can influence the course or expression of depressive mood (pathoplasty and exacerbation models). Failure to show the independence of personality scores from depression scores would lend support to critics' claims that, at least during a depressive episode, personality is unimportant to understanding changes in depression. Evaluating the extent to which both the relative stability and absolute stability of personality can be accounted for in terms of depressive severity is crucial to evaluating the appropriateness of models suggesting (a) that personality is a mere complication of a depressive episode or (b) the result of a common cause that is also responsible for the onset of depression. In the present study, we evaluated the degree to which the relative stability of a personality measure can be attributed to depressive severity by regressing personality assessed at follow-up on (a) measures of depression assessed at baseline and follow-up followed by (b) personality assessed at baseline. If depression and personality measures are interrelated at both baseline and follow-up and if levels of depression are stable across assessments, then any relative stability in personality measures may be due to relative stability of depression measures. However, if personality assessed at baseline still predicts personality assessed at followup, then the relative stability of personality cannot be attributed entirely to depressive severity. To assess the extent to which personality scores are attributed to changes in depression, we used the approach proposed by Trull and Goodwin (1993), which involves regressing change scores for personality measures on change scores for depression measures. If changes in personality can be attributed to changes in depression, support for the view that personality is a complication or arises as result of a cause shared with depression would be strengthened. Failure to demonstrate that change in personality scores is related to change in depression scores weakens the argument that personality is a complication of depressive mood or that changes in both are due to a common cause. Overview Three general issues regarding the stability of personality and the relation between personality during an acute treatment phase for depression were addressed in this study. First, we examined whether relative stability in personality scores can be observed

4 STABILITY AND CHANGE IN PERSONALITY AND DEPRESSION 1357 in a context in which absolute change in personality scores over a short period of time (5 weeks) is likely. Second, we examined the degree to which relative stability in personality scores is related to depressive severity. Third, we examined the degree to which changes in personality scores can be directly attributed to changes in depression scores. All three issues are central to evaluating (a) the appropriateness of models suggesting that personality is a mere complication of a depressive episode or the result of a common cause also responsible for the onset of depression as well as (b) claims by critics of personality and vulnerability models that personality and vulnerability factors are not stable and are state dependent. For illustrative purposes, the present study focused only on the relation between depression and two broad measures of personality, namely neuroticism and extraversion, both of which have been implicated in the clinical presentation of depression (for a review, see Barnett & Gotlib, 1988). To evaluate the generality of our results, we examined the relation between personality and depression with respect to two measures of depression, one self-report measure of depression and one clinician-rated measure of depression. As a result, we were able to assess whether or not results were dependent on shared method variance. Participants Method Participants in the study were drawn from a database of outpatients who were treated within the Mood Disorders Clinic at the Clarke Institute of Psychiatry. Outpatients were administered the Schedule for Affective Disorders and Schizophrenia Lifetime version (SADS-L; Spitzer & Endicott, 1979) and the 17-item Hamilton Rating Scale for Depression (HRSD; Hamilton, 1960) by a trained clinical nurse. The SADS-L interview revealed that, on average, individuals in the study had experienced 3.1 (SD = 2.9, Mode = 2) previous episodes of depression. Preliminary analyses showed that the number of previous episodes was not related to any measure of depression or personality at baseline or follow-up (p s >.40).2 Consequently, results of analyses involving number of previous episodes are not reported in this article. Outpatients also completed a number of self-report symptom measures and personality inventories, including the Beck Depression Inventory (BDI; Beck, Ward, Mendelson, Mock, & Erbaugh, 1961 ) and the NEO Personality Inventory (NEO-P1; Costa & McCrae, 1985, 1989). The HRSD, BDI, and NEO-PI are among the most widely used and validated measures of depression and broad personality dimensions, such as neuroticism and extraversion. In the present study, internal reliability coefficients (Cronbach's alphas) for the BDI and HRSD exceeded.85 at both baseline and follow-up; internal reliability coefficients for NEO- Neuroticism and NEO-Extraversion exceeded.90 at both baseline and follow-up. All outpatients who met the Research Diagnostic Criteria criteria for unipolar, nonpsychotic depression and who were not suffering from any concurrent medical illness were included in the study. Participants had been free of medication for a minimum of 2 weeks prior to being assessed and beginning pharmacotherapy. Forty-one women and 30 men were assessed at baseline, and all 71 outpatients completed measures at follow-up. The majority of men and women in the sample were White, and the mean ages of men and women were 40 and 37 years, respectively. Procedure Diagnostic interviews and baseline measures of depressive severity and personality were completed prior to treatment, All patients received a 5-week trial of antidepressant medication prescribed at the discretion of the treating psychiatrist, according to a treatment algorithm and at adequate doses. All patients initially received a 5-week trial of either desipramine or imipramine, at a dose of 2.5 mg/kg body weight/day, or less if not tolerated, with therapeutic plasma levels, as defined by clinical laboratory, measured during the fifth week. Patients who failed to respond to the first tricyclic then received other adequate trials of antidepressants, including augmentation with lithium, triiodothyronine, substitution with a serotonin reuptake inhibitor, and then, after adequate washout, a trial of a monoamine oxidase inhibitor. After 5 weeks of treatment, outpatients were administered the HRSD and completed symptom and personality measures again. Results First, we report univariate statistics, correlations assessing the relative stability of measures, and change scores. Second, we report the extent to which relative stability can be accounted for by relative differences in depressive severity and assess the utility of personality measures in predicting depressive severity. Third, we evaluate the extent to which change scores from personality measures can be accounted for by change scores in measures of depression. Univariate Statistics, Bivariate Correlations, and Change Scores Measures of personality and depression were related both within and across time of assessment; however, there were some differences between measures of personality and depression. Means, standard deviations, and zero-order correlations among measures of depression and neuroticism are presented in Table 1. Results indicate that test-retest correlations for the HRSD and the BDI were generally similar, as were test-retest correlations for NEO-Neuroticism and NEO-Extraversion. However, test-retest coefficients for personality measures were significantly larger than test-retest coefficients for measures of depression (ps <.001 ). NEO-Neuroticism was related to both self-report and clinician-rated measures of depression at both baseline and follow-up, whereas NEO-Extraversion was unrelated to self-report measures of depression at both baseline and follow-up and were either unrelated or weakly related to clinician-rated measures of depression at baseline and follow-up. NEO-Neuroticism and NEO-Extraversion were weakly, albeit significantly, related both within and across baseline and followup assessments. No significant differences between men and women emerged on any of these indexes. Results for change scores for measures of depression and personality are presented in Table 2. Results in the first portion of the table indicate that overall scores changed significantly for measures of depression and personality. Scores on the BDI, HRSD, and NEO-Neuroticism decreased over time, whereas 2 We examined the relation between number of previous episodes of depression and measures of personality and depression, first by correlating number of episodes with measures of personality and depression and second by examining mean differences on measures of depression and personality between groups of individuals with two or fewer previous episodes of depression or with greater than two previous episodes of depression. No significant associations or differences were found.

5 1358 SANTOR, BAGBY, AND JOFFE Table 1 Descriptive Statistics and Correlations Among Variables Variable M SD 1. HRSD (1) HRSD (2).41"** BDI (1).49***.35** BDI (2).46***.72***.54*** NEO-N (1).31"**.16.52***.28** NEO-N (2).23*.32**.35**.38**.76*** NEO-E (1) " *** NEO-E (2) ** ** -.37**.80*** Note. Boldface coefficients are the test-retest correlations. HRSD = Hamilton Rating Depression Scale; BDI = Beck Depression Inventory; NEO-N = NEO-Neuroticism; NEO-E = NEO-Extraversion. (1) = administered at baseline; (2) = administered at follow-up. *p <.05. **p <.01. ***p <.001. scores on NEO-Extraversion increased over time. Despite significant changes, NEO-Neuroticism scores for both men and women after 5 weeks of treatment were significantly greater than the corresponding age- and gender-matched norms (ps <.001 ), and NEO-Extraversion scores for both men and women after 5 weeks of treatment were significantly smaller than the corresponding age- and gender-matched norms (ps <.001). Results show that a substantial improvement in depressive symptoms was observed over the 5-week treatment period and that a significant reduction in levels of neuroticism paralleled this improvement. Findings are consistent with the numerous studies showing that personality scores change in the context of changes in depressive severity. Again, no significant differences between men and women were observed on any of these indexes. Results for individual facets of NEO-Neuroticism and NEO- Table 2 Absolute Change in Personality and Depression Variable M SE t(70) p A Depression and personality scores HRSD BDI NEO-N NEO-E A Neuroticism facet scores Anxiety Hostility Depression Self-consciousness Impulsiveness ns Vulnerability A Extraversion facet scores Warmth Gregariousness ns Assertiveness Activity Excitement-seeking ns Positive emotions Note. HRSD = Hamilton Rating Depression Scale; BDI = Beck Depression Inventory; NEO-N = NEO-Neuroticism; NEO-E = NEO-Extraversion. Extraversion are also presented in Table 2. Findings indicate that change was observed on all but one facet of Neuroticism and was not limited to facets of Neuroticism, such as anxiety, hostility, and depression, which are most likely to be associated with a reduction in depressive severity. Similarly, change was observed on most facets of Extraversion and was not limited to facets of Extraversion, such as positive emotions and warmth, which are most likely to be associated with an amelioration of depressive severity. As a result, change in NEO-Neuroticism or NEO-Extraversion is not likely to be due entirely to changes in just those facets most strongly related to depressed mood. Results from Tables 1 and 2 suggest that although a significant change in absolute levels of depression and personality was observed over the 5-week trial of pharmacotherapy, personality measures still demonstrated a high degree of relative stability. Change was not limited to facets most strongly related to depressive mood, and despite a considerable change in personality scores observed within a relatively short period of time, personality measures demonstrated the greatest degree of relative stability. Accounting for Relative Stability of Neuroticism and Extraversion Given that some degree of relative stability was observed in measures of depression and that measures of depression were related to measures of Neuroticism and in some instances Extraversion at both follow-up and baseline, we examined the extent to which relative stability in NEO-Neuroticism and NEO-Extraversion might be accounted for by relative differences in depressive severity among individuals at either or both time periods. We used hierarchical regression models to examine the extent to which stability in relative differences among personality scores may be accounted for by individual differences in depressive severity. Given that measures of personality, in particular Neuroticism, and depression were related within time of assessments, the relative stability among individuals' differences in personality from baseline to follow-up may be attributable to individual differences in depressive severity at either baseline or follow-up, or both. For Neuroticism, we regressed follow-up NEO-Neuroticism

6 STABILITY AND CHANGE IN PERSONALITY AND DEPRESSION 1359 scores on (a) baseline and follow-up depression scores followed by (b) baseline NEO-Neuroticism scores. By regressing followup Neuroticism scores on baseline and follow-up depression scores first, one effectively removes any variance in NEO-Neuroticism scores related to depressive severity before examining the relation between follow-up and baseline NEO-Neuroticism scores. Showing that variance in follow-up Neuroticism scores can be predicted from baseline NEO-Neuroticism scores beyond effects due to baseline and follow-up depression scores demonstrates that the relative stability of personality scores cannot be accounted for in terms of depressive severity. Evidence substantiating a relation between follow-up and baseline NEO-Neuroticism scores argues against the view that personality scores are merely a concomitant of depressive severity or the result of a cause shared with depressive severity. Similar analyses were also conducted for NEO-Extraversion. Results are presented in Table 3. A significant amount of variance in follow-up Neuroticism scores could be predicted from variance in both self-report and clinician-rated depression scores in men and women. However, in all instances the greatest amount of variance in follow-up Neuroticism and Extraversion scores was predicted from baseline Neuroticism and Extraversion scores beyond variance accounted for by depression scores assessed at both baseline and follow-up. Findings show that the relative stability of Neuroticism scores cannot be accounted for just in terms of depressive severity, whether assessed with selfreport or clinician-rated measures, and that the relative stability of personality measures is not just a matter of one measure not being entirely attributable to another. Levels of depressive severity at both baseline and follow-up accounted for very little of the variance in personality scores. Modeling Changes in Personality and Depression Results in Table 2 demonstrated that considerable absolute change in both personality and depression scores was observed Table 3 Relative Stability of Neuroticism Scores Accounting for Depressive Severity at Baseline and Follow-Up Dependent Hierarchical Predictor variable order variable R 2 F(1, 67) p NEO-N (2) 1 BDI (2) BDI (1) ns 3 NEO-N (1) NEO-N (2) 1 HRSD (2) HRSD (1) NEO-N (1) NEO-E (2) 1 BDI (2) BDI (1) ns 3 NEO-E (1) NEO-E (2) 1 HRSD (2) ns 2 HRSD (1) ns 3 NEO-E (1) Note. HRSD = Hamilton Rating Depression Scale; BDI = Beck Depression Inventory; NEO-N = NEO-Neuroticism; NEO-E = NEO-Extraversion. (1) = administered at baseline; (2) = administered at followup. over the 5-week treatment protocol. However, the extent to which changes in personality scores can be accounted for by changes in depression scores is unclear. We assessed the extent to which changes in Neuroticism can be accounted for by changes in depression by regressing change scores for Neuroticism on change scores for both self-reported and clinician-rated measures of depression (cf. Trull & Goodwin, 1993). Change scores for Neuroticism were regressed on change scores for either the BDI or the HRSD. Twelve percent of the variance in Neuroticism change scores, F( 1, 69) = 5.77, p <.02, was accounted for by variance in BDI change scores. Similarly, 11% of the variance in Neuroticism change scores, F( I, 69) = 7.38, p <.01, was accounted for by variance in HRSD change scores. In contrast, only a minimal amount of variance in Extraversion scores (5 %) could be accounted for by variance in HRSD change scores, F( 1, 69) = 4.28, p <.04, and no variance in Extraversion scores (<2%) could be accounted for by variance in BDI scores (p >.30). 3 We also examined the relation between changes in specific facets of Neuroticism and depression, given that specific facets of Neuroticism, such as anxiety, self-consciousness, and depression, are likely to be more strongly related to changes in depression than are other facets of Neuroticism, such as hostility, impulsivity, and vulnerability. Results for individual facets of Neuroticism showed that changes in hostility, impulsivity, and vulnerability were unrelated to changes in the BDI or HRSD. A small but significant amount of variance in anxiety (R 2 = 0.06), F(1, 69) = 4.83, p <.03, and self-consciousness (R 2 = 0.08), F(1, 69) = 7.43, p <.01, change scores was accounted for by HRSD change scores, and a small amount of variance in anxiety (R 2 = 0.06), F(I, 69) = 5.30, p <.013, was accounted for by BDI change scores. A moderate variance in depression facet change scores was accounted for by HRSD change scores (R 2 = 0.15), F(1, 69) = 13.22, p <.001, and by BDI change scores (R 2 = 0.10), F(1, 69) = 6.16, p <.02. These results suggest that the relationship between change in personality and change in depressive symptomatology is at best moderate in depressed men and women. These findings were observed with both self-report and clinician-rated measures of depression, and no significant differences between men and women were observed. Discussion The present study addressed a number of issues regarding the stability of personality and the relation between personality and depression. We distinguished relative stability from absolute stability, evaluated the degree to which relative stability in personality scores was related to individual differences in de- 3 Following Trull and Goodwin (1993), we also computed change scores after standardizing baseline and follow-up scores for both personality and depression measure. That is, we regressed change scores for the standardized Neuroticism scores on the change scores for the standardized depression scores. However, no differences in the pattern of results were observed. Careful analysis of residuals for regression models using change scores computed from both raw and standardized measures revealed no extreme leverage or influence points invalidating resuits of the regression models.

7 1360 SANTOR, BAGBY, AND JOFFE pressive severity, and examined whether absolute changes in personality scores were related to absolute changes in depression scores. All of these issues are central to evaluating (a) the appropriateness of models suggesting that personality is a mere complication of a depressive episode or the result of a common cause also responsible for the onset of depression as well as (b) claims by critics of personality and vulnerability models that personality and vulnerability factors are not stable but are state dependent. First, the present results extend findings from longitudinal studies that have focused primarily on personality in a context of stability to the relative stability of personality in a context focusing on acute change. Most research on personality has examined stability in contexts in which little change can be expected, rather than in contexts, such as the course of a clinical trial, in which acute change in levels of depressive severity is the objective. Results showed that even when considerable absolute change is experienced over a very brief period of time, a high degree of relative stability can be observed in personality measures. Second, results showed that both relative stability and absolute change in personality can be observed in the context of acute change in depressive severity. Over the 5-week trial of pharmacotherapy, both personality and depression scores decreased significantly. These findings are consistent with the numerous clinical studies and critical reviews showing that personality scores fall with the amelioration or remission of depressive symptoms (see Barnett & Gotlib, 1988). Results also showed that change was observed across a number of Neuroticism and Extraversion subscales and was not limited to facets most related to negative mood and therefore most likely to be influenced by a change in depressed mood. Despite the considerable absolute change observed in measures of Neuroticism and depression, remarkable stability in the relative differences in Neuroticism among individuals was observed. Results demonstrate there may be two distinct components to stability--relative and absolute stability--and that one does not necessarily entail or presuppose the other. Stability in the relative differences in both individual Neuroticism and Extraversion scores was unaffected by changes in absolute levels of Neuroticism. Third, we examined the extent to which the relative stability of Neuroticism and Extraversion could be accounted for by relative differences in depressive severity. Results showed that the stability in measures of Neuroticism and Extraversion could not be attributed to individual differences in depressive severity, whether assessed with self-report or clinician-rated measures of depression. Relative differences in Neuroticism at one period of time were best accounted for by relative differences in Neuroticism at a second period of time, irrespective of individual differences in depressive severity at both periods of time. Fourth, we evaluated the extent to which changes in personality can be accounted for by changes in depression, a topic that no previous research on depression and personality has addressed. Although critics of personality models have attributed changes in personality scores to changes in depression scores, changes in personality were only modestly accounted for in terms of changes in depression. Only about 12% of the variance of personality change scores could be accounted for in terms of change in depression scores. Changes in both person- ality and depression scores were observed over the 5-week trial of pharmacotherapy; however, change in personality could not be attributed to changes in depressive severity. In summary, these findings show that although absolute changes in personality occur, a high degree of relative stability may also be observed and that both relative stability and absolute change in personality cannot be accounted for directly by individual differences or absolute changes in depressive severity. Although results do not rule out the possibility that personality is influenced by levels of depressive severity in connection with some other variable or that personality in connection with some other variable may influence depression, results showed that personality is not merely a direct concomitant of depressive severity or the direct result of a common cause also responsible for current levels of depression. Implications Critics have argued that personality factors believed to represent a vulnerability to depression are not stable and are therefore state dependent. However, critics have not adequately distinguished relative stability from absolute stability in personality when evaluating the relation of personality to depression. Results from the present study suggest that both claims need to be reconsidered. Personality should not be viewed merely as a direct concomitant of depression or the direct result of a common cause also responsible for the onset of depression. One implication of the present research and indeed one of the central questions in research examining the relation between personality and depression concerns the significance of relative stability in the face of absolute change. Studying the relative stability of personality is important for a number of reasons. First, establishing the relative stability of personality traits and characteristics in the context of change in depressive severity is important for models of personality and depression that hypothesize that personality may influence the course or expression of depression (pathoplasty and exacerbation models). Research has shown that individual differences in personality and vulnerability factors related to depression can influence symptom severity over the course of treatment (Blatt, Zuroff, Quinlan, & Pilkonis, 1996; Sotsky et al., 1991). Any model proposing that personality can influence the course of depression, either directly or indirectly, must show that personality measures remain stable in the context of absolute change. Failure to find evidence for the relative stability of any of these measures precludes considering them as candidates for factors influencing the course or expression of depression. Second, research examining relapse in depression following treatment has suggested that residual symptoms of depression may still represent a risk for relapse (Fava, Grandi, Zielezny, Canestrari, & Morphy, 1994; Thase et al., 1992). Despite dramatic improvement over the course of treatment, residual symptom scores not warranting a diagnosis still constitute an increased risk for symptom return and episode relapse. Understanding the degree of relative stability in both depression and personality may be important for understanding why one individual is more depressed than another at follow-up or possibly more or less likely to relapse (Thase et al., 1992). Identifying stable personality traits or characteristics, like neuroticism, in

8 STABILITY AND CHANGE IN PERSONALITY AND DEPRESSION 1361 the context of acute change in depressive severity may provide researchers with important insights into why one individual shows many or few residual symptoms of depression at the end of treatment despite improvement, why that individual is more or less resistant to change, or is more or less likely to relapse than another. A further implication of this research concerns the factors influencing changes in personality and depression. The present results show that change in personality cannot be accounted for just in terms of change in depression scores and that change in personality can occur in a number of facets, not just those directly related to depression. Moreover, the degree of change in personality related to change in depression was moderate. Failure to account for change in personality on the basis of change in depression weakens the argument that scores on personality measures are merely a complication of depression or the result of a common cause shared with the onset of depression. More complex models that explicitly distinguish relative stability from absolute change are required to understand how personality and depression might be related over the course of an acute treatment protocol. Indeed, there are a number of possibilities that could account for change in personality, including both the direct effects of pharmacological agents on personality and the indirect effects of changes in depression through their influence on other important variables, such as life events or interpersonal environments, which may moderate or mediate the relation between personality and depression. Finally, given the degree of independence between changes in personality and changes in depression, effects of these changes in personality on an individual's level of functioning and general well-being should be considered explicitly. Limitations Concern has been expressed regarding the use of change scores, particularly with respect to the manner in which change scores are distributed and the relation of change scores to initial levels of depressive severity. Because of these concerns, many researchers have adopted the use of residual scores, which in many instances have been viewed as the measure of change, rather than change scores themselves. However, examining residuals is conceptually different from examining depression change scores (cf. Lord, 1967; Rogosa, 1988). Moreover, many of the concerns about difference scores and many of the assumptions regarding the relation between change scores and initial levels of severity are unfounded (see Rogosa, 1988, for a detailed discussion of these issues). Residual scores reflect the degree to which specific individuals have changed more or less than anticipated in the group as a whole, whereas change scores examine the absolute amount of change that has occurred. Examining residuals and examining change scores represent two different but equally important issues. The present findings are most relevant to a depressed outpatient population. Although the depressed outpatient sample used in our study consisted of a large number of individuals with varying degrees of depression, evaluated consecutively at a large urban psychiatric hospital, the sample was predominantly White and is limited in this respect. Accordingly, conclusions may not generalize to outpatient samples from other racial groups. Moreover, findings may not necessarily generalize to outpatients from other diagnostic groups or to other personality variables, such as specific cognitive vulnerability factors like dependency or self-criticism or to measures of personality and depression examined over longer periods of time. However, these findings emphasize the importance of examining the relation between personality and depression within different contexts, including one in which acute change in absolute levels of personality and depression can be expected. These data do require replication. However, findings suggest that the relation between personality and depression is more complex than readily acknowledged. Third, given that the relation between personality and depression was observed in the context of a pharmacological treatment for depression, results may not necessarily generalize to naturalistic changes or to changes occurring as a result of psychotherapy. The relative stability of personality traits in the face of acute change should be examined in a number of contexts and not just in the context of pharmacologically induced mood change. However, findings observed in the present study may not necessarily be limited to pharmacological agents. Results from studies that have compared psychotherapy and pharmacotherapy in treating depression suggest that the relation between individual difference factors and depressive severity over the course of treatment may not vary across treatment modalities (Blatt et al., 1996). Pharmacological agents may not affect the relation between personality factors and depressive severity differently. Conclusion Critics of personality and vulnerability models have generally concluded that personality is not stable and is therefore state dependent on the basis of the numerous studies demonstrating that scores on personality measures decrease with the amelioration of depressive symptoms. However, conclusions regarding the stability of personality and its relation to depression have been drawn (a) without differentiating the concept of relative stability among individual differences from the concept of stability in absolute scores and (b) without explicitly modeling absolute change in personality scores as a function of absolute change in depression scores. In this article, we have explicitly distinguished absolute stability from relative stability in examining the relation between personality and depression and modeled changes in personality as a function of changes in depression. Findings show that although absolute changes in personality may be observed, a high degree of relative stability may also be observed in the context of acute change and that both relative stability of personality and absolute change in personality can not be accounted for directly by individual differences or absolute changes in depressive severity. 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