Five-factor personality traits in patients with seasonal depression: treatment effects and comparisons with bipolar patients

Journal of Affective Disorders 55 (1999) 51–54 www.elsevier.com / locate / jad

Brief report

Five-factor personality traits in patients with seasonal depression: treatment effects and comparisons with bipolar patients Una Jain, Mark A. Blais, Michael W. Otto*, Dina R. Hirshfeld, Gary S. Sachs Massachusetts General Hospital and Harvard Medical School, WACC 815, 15 Parkman St., Boston, MA 02114, USA Received 17 April 1998; accepted 21 August 1998

Abstract Background: Increasingly, the Five Factor Model (FFM) of personality is being used to assess personality characteristics of patients with Axis I disorders. Recent study indicates that patients with the seasonal subtype of major depression (SAD) may differ meaningfully from other depressed patients. In the present study, we further examined this finding, with attention to the stability of personality characteristics across treatment. Methods: We used the NEO-FFM to assess the personality characteristics of two samples of depressed outpatients: patients with SAD and patients with bipolar disorder. Assessment was repeated in the SAD patients after light therapy. Results: Consistent with previous research, we found elevated scores on the Openness domain in the SAD patients. SAD patients also scored significantly lower on Neuroticism and significantly higher on the Conscientiousness and Extroversion domains than patients with bipolar disorder. Scores on the Openness domain remained elevated after treatment of SAD; this occurred in the context of significant decreases in Neuroticism and increases in Extroversion scores. Limitations: These results were obtained in a relatively small-sample study. Although our sample of bipolar patients were taking mood stabilizers, it is unlikely that medication effects could explain our results. Conclusions: Our findings are consistent with those reported by Bagby et al. (Major depression and the five-factor model of personality. J. Pers. Disord. 1995;9:224–234) and suggests that Neuroticism and Extroversion are the FFM domains most responsive to treatment for depression. Our results also suggest that elevations on the Openness domain do not change with treatment and may be an enduring characteristic of patients with SAD.  1999 Elsevier Science B.V. All rights reserved. Keywords: Personality; Depression; Seasonal affective disorder; Five factor model; NEO

1. Introduction The Five Factor Model (FFM) of personality, an empirically derived system, has received increasing *Corresponding author. Tel.: 1 1-617-7263488; fax: 1 1-6177267541.

support as a valid model for measuring and describing normal personality (Costa and McCrae, 1989; Digman, 1990). According to the FFM, normal personality can be adequately described by five broad bipolar domains: (1) Neuroticism–Emotional Stability, (2) Extroversion–Introversion, (3) Openness to Experience–Closed to Experience, (4) Agree-

0165-0327 / 99 / $ – see front matter  1999 Elsevier Science B.V. All rights reserved. PII: S0165-0327( 98 )00206-7

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ableness–Disagreeableness, and (5) Conscientiousness–Non-Conscientiousness. The most popular measures of the FFM are the NEO-Personality Inventory (NEO-PI: Costa and McCrae, 1989) and the shorter version, the NEO-Five Factor Model (NEO-FFM: Costa and McCrae, 1989). Recent studies by Bagby et al. (1995) used the FFM to explore personality characteristics of patients with major depression and seasonal depressive disorder (Bagby et al., 1996). In the first of these studies, Bagby et al. (1995) measured the FFM characteristics of depressed patients before and after treatment and found that the domains of Neuroticism and Extroversion changed significantly with treatment, but Openness, Agreeableness, and Conscientiousness did not. In a second study, Bagby et al. (1996) compared the FFM personality characteristics of patients with Seasonal Affective Disorder (SAD) to patients with non-psychotic major depression. When the severity of depression was controlled statistically, the SAD group scored significantly higher on the FFM Openness domain. Furthermore, the SAD group’s mean score on Openness was a full standard deviation above the normative group. High scores on the FFM Openness domain characterize individuals who are described as imaginative, emotionally sensitive, and willing to entertain unconventional ideas (Costa and McCrae, 1989). Bagby et al. (1996) suggested that elevations on two facets of Openness (Aesthetics and Feelings) may help explain the apparent emotional sensitivity to the environment (seasonal changes in light) characteristic of SAD. Elevations on the Aesthetics facet is characteristic of individuals who are highly sensitive to their internal and external environment, and elevations on the Feelings facet characterize individuals who experience moods more intensely than others. As suggested by Bagby et al. (1996), the sensitivity to environmental changes combined with a tendency toward amplification of moods may potentiate the emergence of SAD. Although research suggests that the FFM domain of Openness is unrelated to state depression in patients without SAD (Schuller et al., 1993; Bagby et al., 1995), it is unclear whether elevated Openness domain scores are stable in recovered patients with SAD. The present study further examines the issue of personality trait differences between patients with

SAD and non-SAD depression. The present study, compares FFM scores for SAD patients before and after treatment, and compares pretreatment scores of these subjects to FFM scores from a sample of depressed patients with bipolar disorder.

2. Methods Patients giving informed written consent for entry into depression treatment protocols at the Bipolar Research Program outpatient clinic at Massachusetts General Hospital are evaluated by experienced research psychiatrists using the structured interview for DSM-III-R (SCID-P; Spitzer et al., 1980) with a supplemental module to evaluate seasonality of affective episodes. Subjects were included in this analysis if they were assigned a diagnosis of unipolar depression with seasonal pattern (SAD; n 5 24) or bipolar disorder, depressed episode, non-seasonal subtype (n 5 13) and had not used antidepressant medication for at least 2 weeks before the baseline. All patients with bipolar disorder were taking moodstabilizing medications (carbamazepine, lithium, and / or divalproex sodium) at the time of assessment. At the baseline evaluation, depressive symptoms were rated on the 17-item Hamilton depression rating scale (HAM-D; Hamilton, 1960; Williams, 1988), and subjects completed self-report questionnaires including the NEO-FFM (Costa and McCrae, 1989). The two groups of patients did not differ in sex distribution (SAD: five women and 19 men; Bipolar: six women and seven men) or HAM-D depression severity. Subjects meeting criteria for SAD participated in a treatment protocol using light therapy with either a 10 000-lux light box or a dawn simulator. The NEOFFM and HAM-D were readministered to the SAD subjects after 6 weeks of light therapy. Subjects meeting criteria for bipolar disorder, depressed episode, non-seasonal subtype were referred to ongoing studies in the bipolar clinic. Analysis of covariance (ANCOVA) was used to assess the differences between the two groups of depressed patients on the five domains of the NEOFFM, with depression severity (assessed by the HAM-D) serving as the covariate. Differences in NEO-FFM domain scores across treatment were

U. Jain et al. / Journal of Affective Disorders 55 (1999) 51 – 54

assessed with correlated t-tests for the sample of 20 SAD patients with data available. To control for multiple comparisons in each of these analyses, a conservative critical value was set at P 5 0.05 / 5 5 0.01.

3. Results Table 1 presents demographic characteristics, depression severity, and the NEO-FFM domain scores (T-scores) for subjects in each group. In the ANCOVA analyses, the covariate (depression severity) was not a significant predictor of NEO-FFM domain scores (all P-values . 0.31). Significant differences between groups were evident for four of five of the NEO-FFM domain scores. Patients with SAD scored significantly lower than the bipolar patients on Neuroticism (F 5 16.57; df 5 1,37; P , 0.0001), and significantly higher on the Extroversion (F 5 7.30; df 5 1,37; P , 0.01), Openness (F 5 11.05; df 5 1,37; P , 0.0001), and Conscientiousness (F 5 4.49; df 5 1,37; P , 0.04) domain scales. No significant differences between groups were evident for the Agreeableness domain (F 5 2.73; df 5 1,37; ns). Table 2 presents the means and standard deviations of the NEO-FFM domain scores and HAM-D for a subsample of 20 patients with SAD who completed post-treatment assessments. Paired t-tests comparing baseline and week-6 HAM-D scores for

Table 1 Means and standard deviations for the clinical characteristics of SAD and bipolar patients Variable

Age HAM-D Neuroticism Extroversion Agreeableness Openness Conscientiousness

Mean6S.D.

P-value

SAD (n 5 24)

Bipolar (n 5 13)

38.069.9 27.566.5 60.3612.2 41.9612.1 45.4611.5 62.368.5 41.0611.2

35.7611.6 23.867.9 72.564.7 33.269.5 39.6612.8 50.7612.2 34.167.4

ns ns 0.0001 0.01 ns 0.0001 0.04

Note: NEO-FFM domains are expressed as T-scores (with a normological mean of 50 and standard deviation of 10). P-values are for the significance of differences between groups in the ANCOVA; ns 5 not significant.

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Table 2 Means and standard deviations of HAM-D and NEO-FFM domain scores for SAD patients completing post-treatment assessments Variable

HAM-D Neuroticism Extroversion Openness Agreeableness Conscientiousness

Mean6S.D. (N 5 20) Pre-Tx

Post-Tx

26.665.8 59.3612.5 43.8611.9 63.567.3 46.0610.7 40.5610.8

7.468.7 52.1610.8 46.9611.6 63.566.7 47.969.7 41.7610.6

P-value

0.0001 0.004 0.05 ns ns ns

Note: NEO-FFM domains are expressed as T-scores (with a normological mean of 50 and standard deviation of 10). P-values are for the significance of paired t-test comparisons; ns 5 not significant.

SAD subjects demonstrated a significant reduction in depression severity (t 5 10.2, df 5 19, P , 0.0001). Of the five NEO-FFM domain scores, only Neuroticism demonstrated a significant reduction across treatment according to conservative critical values (t 5 3.27, df 5 19, P , 0.004). A trend toward greater Extroversion post-treatment was significant only at standard critical values (t 5 2.17, df 5 19, P , 0.05); no other differences approached significance (all P values . 0.22).

4. Discussion In a small sample of depressed outpatients we found evidence of significant difference in NEOFFM personality dimensions among patients with SAD relative to bipolar depression. Our findings of higher scores on the domain of Openness to Experience replicated the recent report by Bagby et al. (1996) comparing SAD patients to a sample of nonseasonal unipolar depressives. In addition, our sample of SAD patients scored significantly lower on Neuroticism, and significantly higher on the Extroversion and Conscientiousness domains than our bipolar sample. It is unclear whether these findings are specific to the traits of SAD patients, bipolar patients, or both. Our methods do not rule out the possibility that our findings reflect the psychotropic influence of mood stabilizing medication in the bipolar patients, although medication effects are unlikely to explain the

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higher neuroticism scores among these patients. Moreover, severity of depression did not account for the differences observed between the SAD and bipolar groups. Treatment of patients with SAD resulted in a significant decrease in Neuroticism scores and a trend (significant according to a standard critical value only) toward increased Extroversion scores. This finding is consistent with results reported by Bagby et al. (1995) and suggests that Neuroticism and Extroversion are the FFM domains most responsive to treatment for depression, perhaps reflecting the greater disruption of these domains by depressive disorders. Post-treatment scores on Neuroticism, Extroversion, Agreeableness, and to a lesser extent, Conscientiousness were well within the range of norm expectation. The Openness domain remained elevated after treatment in the SAD cohort. The absence of a significant post-treatment change in Openness, along with a post-treatment mean score greater than one standard deviations above norm expectation, suggests that elevations on this domain may be an enduring characteristic of patients with SAD.

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