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The relationship between mood instability and depression: Implications for studying and treating depression
Medical Hypotheses 81 (2013) 459–462
Contents lists available at SciVerse ScienceDirect
Medical Hypotheses journal homepage: www.elsevier.com/locate/mehy
The relationship between mood instability and depression: Implications for studying and treating depression R.C. Bowen ⇑, Y. Wang, L. Balbuena, A. Houmphan, M. Baetz Department of Psychiatry, University of Saskatchewan, 103 Hospital Drive, Saskatoon, Saskatchewan S7N 0W8, Canada
a r t i c l e
i n f o
Article history: Received 22 April 2013 Accepted 15 June 2013
a b s t r a c t Background: Most individuals with depressed mood report mood fluctuations (Mood Instability) within hours or days. This is not recognized in diagnostic criteria or standard rating scales for depression. Hypothesis: That mood instability is a distinct component of the development of depression that has been omitted from criteria for depression because of reliance on retrospective recall and structured interviews. The inclusion of Mood Instability would enhance research into causes and treatment of depression. Studies: We examined three datasets that used retrospective and prospective measures of depressed symptom ratings and mood instability to determine the relationship between the two. Study 1 used data from the 1991 UK Health and Lifestyle Surveys (HALS). Studies 2 and 3 used clinical samples. The scales used to assess mood instability were the mood instability factor from the Eysenck Personality Inventory Neuroticism Scale, the Affective Lability Scale (ALS), and the Visual Analogue Depression Scale (VAS). The depression scales (depressive symptoms) were the General Health Questionnaire (GHQ) depression factor, the Beck Depression Inventory IA (BDI) and the mean from the Visual Analogue Depression Scale (VAS). We used partial correlation analysis to assess the association between mood instability and depression and exploratory factor analysis to determine the factor structure of items pooled from the mood instability and depression scales from studies 1 and 2. Results: Mood Instability was found to be moderately associated with depressive symptoms. The Pearson’s r-values ranged from 0.49 to 0.57. The correlation was lower when recalling mood in the past. The factor analytic solution supported the hypothesis that MI and depressive symptoms are related but distinct constructs. Conclusions: Reliance exclusively on the retrospective assessment of depressive symptoms has occluded the widespread occurrence of mood instability. Including Mood Instability in diagnostic and assessment criteria would enhance causal and treatment research in depression. Ó 2013 Elsevier Ltd. All rights reserved.
Introduction In psychiatry, most of the data for a diagnosis of a depressive syndrome is obtained from the patient through retrospective recall, augmented by direct observation during the interview. The diagnosis is made if a number of symptoms are present over a specified duration (and other criteria such as no obvious physical cause are met) [1,2]. In DSM-IV, an episode of Major Depression is described as ‘‘depressed mood most of the day, nearly every day, as indicated by either subjective report (e.g. feels sad or empty) or observation. . .’’ [3]. ‘‘Nearly every day’’ allows for some variation of depressed mood, but also implies that significant mood fluctuations are incompatible with the definition of Major Depression. If mood fluctuations are present and the number of symptoms or duration of fluctuations do not meet criteria for Bipolar Disor-
⇑ Corresponding author. Tel.: +1 (306) 966 8226; fax: +1 (306) 966 8237. E-mail address: [email protected] (R.C. Bowen). 0306-9877/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.mehy.2013.06.010
ders, then the condition is likely to be classified as a Personality Disorder or ignored [4]. Common rating scales used in clinical research are similar to DSM and ICD-10 diagnostic criteria in listing a number of symptoms that are summed, whether the symptoms are self-rated [5] or observer rated [6]. These diagnostic criteria and rating scales have become the gold standard for psychiatric research and drug trials. In this paper we will also use ‘‘depression’’ to mean a summation of a number of past or current typical clinical symptoms, usually with a stipulated minimum duration (e.g. 1 week for the BDI-IA) [5]. Numerous clinical research reports have noted that many patients with mood symptoms also report subsyndromal mood fluctuations [7,8]. The fluctuations occur within hours or days so they are not usually observed during the typical interview. However, studies using serial prospective measurements have confirmed the finding [9] [10–12]. These fluctuations are operationalized as mood instability, defined as severe and frequent fluctuations of mood over time [13]. Mood Instability is higher in various patient groups with mood symptoms than in control populations
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R.C. Bowen et al. / Medical Hypotheses 81 (2013) 459–462
[9,12–14]. It has also been shown that MI contributes to suicidal thinking [15–16], subjective distress [17], disability [18] and health service use [14]. The terms mood swings, mood variability, affective instability, emotional labililty, affective and mood dysregulation and Mood Instability have similar meanings, with subtle differences due to different origins. We hypothesize that Mood Instability and depression (as assessed by diagnostic criteria and rating scales) are related, but are also distinct concepts, and more specifically that they are positively but only moderately correlated [11]. The corollary is that research into causes and treatment of depression is lacking and the omission of Mood Instability is one reason why it has failed to progress [19].
[24]. These changes include switches from anxiety to depression, depression to elation, and depression to anger. Subjects rate how much a particular statement applies to them on a 4 point Likert scale ranging from ‘‘very undescriptive’’ to ‘‘very descriptive’’. Mood Instability and Mean Depression: Participants in Study 3 completed twice daily visual analogue scales (VAS) just after arising and just before bedtime for seven consecutive days [30]. The prompt was ‘‘In the last few hours I felt depressed’’; the anchors were ‘‘not at all’’ to ‘‘very much so’’. We calculated Mood Instability with the mean square successive difference statistic (MSSD) [31]. The average of 14 ratings represents the mean VAS Depression score [32]. Data analysis
Settings and subjects Study 1: We performed a secondary analysis of the 1991 Health and Lifestyle Survey (HALS) [20]. This representative survey of the populations of England, Scotland, and Wales included 3519 individuals who completed the Eysenck Personality Inventory (EPI) [21] and General Health Questionnaire (GHQ) [22,23]. Participants ranged in age from 18 to 94 years with the average age being 44.9 years (median = 43, SD = 15.2) and 55.25% were female. Study 2: Referrals to the practices of 5 psychiatrists and a community based anxiety and mood programme completed the Affective Lability Scale (ALS) [24] and Beck Depression Inventory (BDI1A) [5] before their initial assessment. Of 641 potential recruits, 440 provided complete data and gave written consent. The participants ranged in age from 13 to 78 years (mean = 38.9, SD = 12.6) and 67.5% were female. Formal diagnoses were not available for these patients. Study 3: Data from participants in 5 studies who prospectively completed visual analogue scale mood diaries over a week and the BDI and provided consent were aggregated [12,25–27]. There were 103 patients and 94 control participants who were health care professionals or graduate students. The participants ranged in age from 15 to 64 with a mean age of 43 years (median = 32, SD = 28.9) with 75.8% being female. The patients were assessed using the MINI diagnostic interview [28]. All of the 103 patients complained of depressive symptoms and 102 had a primary diagnosis of an anxiety disorder, 40 had experienced major depression and 44 had a history of a bipolar mood disorder. Study instruments The Eysenck Personality Inventory (EPI) used in Study 1 (HALS) is a 57-item questionnaire that includes a neuroticism subscale (EPI-N) with 24 ‘‘yes/no’’ items [21]. We have previously factor analyzed the EPI-N subscale and derived a 7-item Mood Instability factor (EPI-N (MI)) [18]. Other researchers using the same data have independently extracted the same factor that they labelled ‘‘mood lability [29].’’ The General Health Questionnaire (GHQ) also used in Study 1 is a measure of psychological wellbeing in the community [22]. It consists of 30 Likert scale questions that range from ‘‘less than usual’’ to ‘‘much more than usual’’. Based on the HALS data, a 6-item depression factor has been derived that we used in Study 1 as a measure of depression [23]. The Beck Depression Inventory (BDI-1A) used in Studies 2 and 3 is a 21-item self-report questionnaire graded on a 4-point scale. The time frame is 1 week. In study 3, the BDI was completed during the same week as the visual analogue scale (see below). Statements are presented in the first-person and subjects select the item that best reflects their recent state (‘‘I feel sad’’). The Affective Lability Scale (ALS) also used in Study 2 is an 18item self-report questionnaire for measuring changes in mood
In each study we correlated the measure of depression with the measure of Mood Instability. Partial correlations removed the effects of age and sex in all calculations. For Study 1, we correlated the EPI-N (MI) with GHQ depression. For Study 2, we correlated the ALS with the BDI. The measures in Studies 1 and 2 are all retrospective. In Study 3, we correlated Mood Instability (MSSD) (prospective) with the BDI (concurrent) (Study 3a) and Mood Instability (prospective) with mean VAS (prospective) (Study 3b). In Studies 1 and 2, we performed an exploratory factor analysis of the pooled items from the depression and Mood Instability scales for the two studies separately. The integrity of this procedure hinges on extracting the correct number of factors so we used Velicer’s minimum average partial (MAP) test [33]. Velicer’s test recommended 2 factors for study 1 and 5 factors for Study 2. Factor analysis was performed using the iterated principal factors method with oblique oblimin rotation. Results The correlations are tabulated in Table 1. The results show that the correlations are in the moderate range with r-values between 0.41 and 0.57. The highest correlation is between the two prospective measures in Study 3b (r = 0.57) and the lowest between the two retrospective measures in Study 1 (r = 0.41). The factor analytic solution for Study 1 indicated a segregation of depression and Mood Instability items (Fig. 1, upper panel). The factor analytic solution for Study 2 (Fig. 1, lower panel) closely resembled a two-factor solution for the BDI-I [34] and the threefactor structure of the ALS-Short Form [24]. (Detailed factor solutions and item loadings are available upon request.) The sole exception was BDI # 11 (irritability) which loaded with four ALS items assessing switches into anger. Discussion The main finding is a modest correlation between Mood Instability and depression (depressive symptoms) across all three studies. The finding held for three measures of depression and three measures of Mood Instability, irrespective of whether the Table 1 Summary of samples, measures, and results. Correlation of Mood Instability (MI) measures with depression measures. Study
N
MI
Depression
Time frame
r value (95% CI)
1 2 3a
3374 440 159
EPI-N (MI) ALS MSSD
GHQ-D BDI Mean VAS
0.41 (0.38–0.44) 0.49 (0.42–0.56) 0.57 (0.46–0.67)
3b
197
MSSD
BDI
Retrospective Retrospective Real time prospective Retrospective but concurrent
0.49 (0.38–0.59)
Note: These are partial correlations with the effects of age and sex partialed out.
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Fig. 1. Factor solutions for depression and mood instability.
measures were retrospective or prospective, and whether the samples were drawn from the general or clinical populations. This is consistent with the findings of previous studies [11,16,35]. The factor analytic separation of Mood Instability and depression into non-overlapping factors supports the conclusion that they are related but distinct concepts. The second finding is that the correlation between Mood Instability and depression appears to be smaller for retrospective data compared with concurrent data. This is also consistent with the literature showing that memory for personal psychological events tends to be more general and less specific in people with mood problems [36,37] and this deficit is particularly noticeable for high moods [38]. A heuristic explanation for the results is that the traditional conception of depression as a syndrome consisting of state-like symptoms and the more recent finding of Mood Instability as an ongoing proclivity to unstable moods are complementary ways of assessing the global experience of depressed mood [39]. We propose that repeated unexpected precipitous decreases from euthymic or positive mood contribute over time to the overall experience of depression, along with stressful life events [40–42]. Because the brief activated or euthymic episodes of mood are not easily recalled, overall mood is reported as level of depression in a summary statement in clinical and research interviews [39]. This is most likely to occur when the interview is structured as in research settings. The result has been omission of Mood Instability from diagnostic criteria [1,2] and common rating scales. This argument does not preclude biological factors and brain changes that occur with depression [43]. The alternate explanation is that a large proportion of the population with depressive symptoms also have personality disorders [44], but this is a conceptual and definitional issue. Several studies have shown that Mood Instability is common in patients with anxiety disorders, mood disorders, alcohol abuse and the borderline personality disorder [12,25–27,42]. These latter findings are more consistent with our previous report that Mood Instability is the key component of neuroticism and not limited to the diagnostic category of personality disorders [18]. The argument has already been made that ‘‘depression’’ and Major Depression are ‘‘first level identifiers of a psychological state’’ independent of cause or outcome [45]. We are not proposing that Mood Instability is a differ-
ent type of depression, or a comorbid condition, and Mood Instability should certainly not be reified. The data and clinical experience suggest that Mood Instability is a necessary descriptor of disordered depressed mood. Consequently, we recommend that specific questions about Mood Instability be incorporated into clinical and research interviews, and also into criteria for the depressive syndrome. This could lead to improved treatment results [46], more accurate suicide assessment [47], and more progress in developing new causal hypotheses [19] and would be more compatible with a model of mood disorders as chronic complex disorders [48]. There are limitations to our argument based on the studies. In Studies 1 and 2, the measures of Mood Instability (EPI-N Mood Instability factor and ALS) are retrospective scales and liable to recall bias but they do focus attention on Mood Instability. The clinical samples in studies 2 and 3 are from one centre. This paper addresses the relationship of Mood Instability with depression assessed as a summation of symptoms; future studies might also include diagnostic assessments.
Conclusions Traditional depression diagnostic criteria and questionnaires are limited because inquiry about Mood Instability has been omitted. We propose that measures of Mood Instability should be added to clinical and research interviews. This could enhance the search for causes of mood disorders and their treatment, but the proof would lie in the research results.
Conflict of interest statement There are no potential conflicts of interest to declare.
Acknowledgement This research was supported by the Department of Psychiatry. Mr. Y. Yang and Mr. A. Houmphan were supported by funding from the Dean of Medicine.
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Contents lists available at SciVerse ScienceDirect
Medical Hypotheses journal homepage: www.elsevier.com/locate/mehy
The relationship between mood instability and depression: Implications for studying and treating depression R.C. Bowen ⇑, Y. Wang, L. Balbuena, A. Houmphan, M. Baetz Department of Psychiatry, University of Saskatchewan, 103 Hospital Drive, Saskatoon, Saskatchewan S7N 0W8, Canada
a r t i c l e
i n f o
Article history: Received 22 April 2013 Accepted 15 June 2013
a b s t r a c t Background: Most individuals with depressed mood report mood fluctuations (Mood Instability) within hours or days. This is not recognized in diagnostic criteria or standard rating scales for depression. Hypothesis: That mood instability is a distinct component of the development of depression that has been omitted from criteria for depression because of reliance on retrospective recall and structured interviews. The inclusion of Mood Instability would enhance research into causes and treatment of depression. Studies: We examined three datasets that used retrospective and prospective measures of depressed symptom ratings and mood instability to determine the relationship between the two. Study 1 used data from the 1991 UK Health and Lifestyle Surveys (HALS). Studies 2 and 3 used clinical samples. The scales used to assess mood instability were the mood instability factor from the Eysenck Personality Inventory Neuroticism Scale, the Affective Lability Scale (ALS), and the Visual Analogue Depression Scale (VAS). The depression scales (depressive symptoms) were the General Health Questionnaire (GHQ) depression factor, the Beck Depression Inventory IA (BDI) and the mean from the Visual Analogue Depression Scale (VAS). We used partial correlation analysis to assess the association between mood instability and depression and exploratory factor analysis to determine the factor structure of items pooled from the mood instability and depression scales from studies 1 and 2. Results: Mood Instability was found to be moderately associated with depressive symptoms. The Pearson’s r-values ranged from 0.49 to 0.57. The correlation was lower when recalling mood in the past. The factor analytic solution supported the hypothesis that MI and depressive symptoms are related but distinct constructs. Conclusions: Reliance exclusively on the retrospective assessment of depressive symptoms has occluded the widespread occurrence of mood instability. Including Mood Instability in diagnostic and assessment criteria would enhance causal and treatment research in depression. Ó 2013 Elsevier Ltd. All rights reserved.
Introduction In psychiatry, most of the data for a diagnosis of a depressive syndrome is obtained from the patient through retrospective recall, augmented by direct observation during the interview. The diagnosis is made if a number of symptoms are present over a specified duration (and other criteria such as no obvious physical cause are met) [1,2]. In DSM-IV, an episode of Major Depression is described as ‘‘depressed mood most of the day, nearly every day, as indicated by either subjective report (e.g. feels sad or empty) or observation. . .’’ [3]. ‘‘Nearly every day’’ allows for some variation of depressed mood, but also implies that significant mood fluctuations are incompatible with the definition of Major Depression. If mood fluctuations are present and the number of symptoms or duration of fluctuations do not meet criteria for Bipolar Disor-
⇑ Corresponding author. Tel.: +1 (306) 966 8226; fax: +1 (306) 966 8237. E-mail address: [email protected] (R.C. Bowen). 0306-9877/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.mehy.2013.06.010
ders, then the condition is likely to be classified as a Personality Disorder or ignored [4]. Common rating scales used in clinical research are similar to DSM and ICD-10 diagnostic criteria in listing a number of symptoms that are summed, whether the symptoms are self-rated [5] or observer rated [6]. These diagnostic criteria and rating scales have become the gold standard for psychiatric research and drug trials. In this paper we will also use ‘‘depression’’ to mean a summation of a number of past or current typical clinical symptoms, usually with a stipulated minimum duration (e.g. 1 week for the BDI-IA) [5]. Numerous clinical research reports have noted that many patients with mood symptoms also report subsyndromal mood fluctuations [7,8]. The fluctuations occur within hours or days so they are not usually observed during the typical interview. However, studies using serial prospective measurements have confirmed the finding [9] [10–12]. These fluctuations are operationalized as mood instability, defined as severe and frequent fluctuations of mood over time [13]. Mood Instability is higher in various patient groups with mood symptoms than in control populations
460
R.C. Bowen et al. / Medical Hypotheses 81 (2013) 459–462
[9,12–14]. It has also been shown that MI contributes to suicidal thinking [15–16], subjective distress [17], disability [18] and health service use [14]. The terms mood swings, mood variability, affective instability, emotional labililty, affective and mood dysregulation and Mood Instability have similar meanings, with subtle differences due to different origins. We hypothesize that Mood Instability and depression (as assessed by diagnostic criteria and rating scales) are related, but are also distinct concepts, and more specifically that they are positively but only moderately correlated [11]. The corollary is that research into causes and treatment of depression is lacking and the omission of Mood Instability is one reason why it has failed to progress [19].
[24]. These changes include switches from anxiety to depression, depression to elation, and depression to anger. Subjects rate how much a particular statement applies to them on a 4 point Likert scale ranging from ‘‘very undescriptive’’ to ‘‘very descriptive’’. Mood Instability and Mean Depression: Participants in Study 3 completed twice daily visual analogue scales (VAS) just after arising and just before bedtime for seven consecutive days [30]. The prompt was ‘‘In the last few hours I felt depressed’’; the anchors were ‘‘not at all’’ to ‘‘very much so’’. We calculated Mood Instability with the mean square successive difference statistic (MSSD) [31]. The average of 14 ratings represents the mean VAS Depression score [32]. Data analysis
Settings and subjects Study 1: We performed a secondary analysis of the 1991 Health and Lifestyle Survey (HALS) [20]. This representative survey of the populations of England, Scotland, and Wales included 3519 individuals who completed the Eysenck Personality Inventory (EPI) [21] and General Health Questionnaire (GHQ) [22,23]. Participants ranged in age from 18 to 94 years with the average age being 44.9 years (median = 43, SD = 15.2) and 55.25% were female. Study 2: Referrals to the practices of 5 psychiatrists and a community based anxiety and mood programme completed the Affective Lability Scale (ALS) [24] and Beck Depression Inventory (BDI1A) [5] before their initial assessment. Of 641 potential recruits, 440 provided complete data and gave written consent. The participants ranged in age from 13 to 78 years (mean = 38.9, SD = 12.6) and 67.5% were female. Formal diagnoses were not available for these patients. Study 3: Data from participants in 5 studies who prospectively completed visual analogue scale mood diaries over a week and the BDI and provided consent were aggregated [12,25–27]. There were 103 patients and 94 control participants who were health care professionals or graduate students. The participants ranged in age from 15 to 64 with a mean age of 43 years (median = 32, SD = 28.9) with 75.8% being female. The patients were assessed using the MINI diagnostic interview [28]. All of the 103 patients complained of depressive symptoms and 102 had a primary diagnosis of an anxiety disorder, 40 had experienced major depression and 44 had a history of a bipolar mood disorder. Study instruments The Eysenck Personality Inventory (EPI) used in Study 1 (HALS) is a 57-item questionnaire that includes a neuroticism subscale (EPI-N) with 24 ‘‘yes/no’’ items [21]. We have previously factor analyzed the EPI-N subscale and derived a 7-item Mood Instability factor (EPI-N (MI)) [18]. Other researchers using the same data have independently extracted the same factor that they labelled ‘‘mood lability [29].’’ The General Health Questionnaire (GHQ) also used in Study 1 is a measure of psychological wellbeing in the community [22]. It consists of 30 Likert scale questions that range from ‘‘less than usual’’ to ‘‘much more than usual’’. Based on the HALS data, a 6-item depression factor has been derived that we used in Study 1 as a measure of depression [23]. The Beck Depression Inventory (BDI-1A) used in Studies 2 and 3 is a 21-item self-report questionnaire graded on a 4-point scale. The time frame is 1 week. In study 3, the BDI was completed during the same week as the visual analogue scale (see below). Statements are presented in the first-person and subjects select the item that best reflects their recent state (‘‘I feel sad’’). The Affective Lability Scale (ALS) also used in Study 2 is an 18item self-report questionnaire for measuring changes in mood
In each study we correlated the measure of depression with the measure of Mood Instability. Partial correlations removed the effects of age and sex in all calculations. For Study 1, we correlated the EPI-N (MI) with GHQ depression. For Study 2, we correlated the ALS with the BDI. The measures in Studies 1 and 2 are all retrospective. In Study 3, we correlated Mood Instability (MSSD) (prospective) with the BDI (concurrent) (Study 3a) and Mood Instability (prospective) with mean VAS (prospective) (Study 3b). In Studies 1 and 2, we performed an exploratory factor analysis of the pooled items from the depression and Mood Instability scales for the two studies separately. The integrity of this procedure hinges on extracting the correct number of factors so we used Velicer’s minimum average partial (MAP) test [33]. Velicer’s test recommended 2 factors for study 1 and 5 factors for Study 2. Factor analysis was performed using the iterated principal factors method with oblique oblimin rotation. Results The correlations are tabulated in Table 1. The results show that the correlations are in the moderate range with r-values between 0.41 and 0.57. The highest correlation is between the two prospective measures in Study 3b (r = 0.57) and the lowest between the two retrospective measures in Study 1 (r = 0.41). The factor analytic solution for Study 1 indicated a segregation of depression and Mood Instability items (Fig. 1, upper panel). The factor analytic solution for Study 2 (Fig. 1, lower panel) closely resembled a two-factor solution for the BDI-I [34] and the threefactor structure of the ALS-Short Form [24]. (Detailed factor solutions and item loadings are available upon request.) The sole exception was BDI # 11 (irritability) which loaded with four ALS items assessing switches into anger. Discussion The main finding is a modest correlation between Mood Instability and depression (depressive symptoms) across all three studies. The finding held for three measures of depression and three measures of Mood Instability, irrespective of whether the Table 1 Summary of samples, measures, and results. Correlation of Mood Instability (MI) measures with depression measures. Study
N
MI
Depression
Time frame
r value (95% CI)
1 2 3a
3374 440 159
EPI-N (MI) ALS MSSD
GHQ-D BDI Mean VAS
0.41 (0.38–0.44) 0.49 (0.42–0.56) 0.57 (0.46–0.67)
3b
197
MSSD
BDI
Retrospective Retrospective Real time prospective Retrospective but concurrent
0.49 (0.38–0.59)
Note: These are partial correlations with the effects of age and sex partialed out.
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Fig. 1. Factor solutions for depression and mood instability.
measures were retrospective or prospective, and whether the samples were drawn from the general or clinical populations. This is consistent with the findings of previous studies [11,16,35]. The factor analytic separation of Mood Instability and depression into non-overlapping factors supports the conclusion that they are related but distinct concepts. The second finding is that the correlation between Mood Instability and depression appears to be smaller for retrospective data compared with concurrent data. This is also consistent with the literature showing that memory for personal psychological events tends to be more general and less specific in people with mood problems [36,37] and this deficit is particularly noticeable for high moods [38]. A heuristic explanation for the results is that the traditional conception of depression as a syndrome consisting of state-like symptoms and the more recent finding of Mood Instability as an ongoing proclivity to unstable moods are complementary ways of assessing the global experience of depressed mood [39]. We propose that repeated unexpected precipitous decreases from euthymic or positive mood contribute over time to the overall experience of depression, along with stressful life events [40–42]. Because the brief activated or euthymic episodes of mood are not easily recalled, overall mood is reported as level of depression in a summary statement in clinical and research interviews [39]. This is most likely to occur when the interview is structured as in research settings. The result has been omission of Mood Instability from diagnostic criteria [1,2] and common rating scales. This argument does not preclude biological factors and brain changes that occur with depression [43]. The alternate explanation is that a large proportion of the population with depressive symptoms also have personality disorders [44], but this is a conceptual and definitional issue. Several studies have shown that Mood Instability is common in patients with anxiety disorders, mood disorders, alcohol abuse and the borderline personality disorder [12,25–27,42]. These latter findings are more consistent with our previous report that Mood Instability is the key component of neuroticism and not limited to the diagnostic category of personality disorders [18]. The argument has already been made that ‘‘depression’’ and Major Depression are ‘‘first level identifiers of a psychological state’’ independent of cause or outcome [45]. We are not proposing that Mood Instability is a differ-
ent type of depression, or a comorbid condition, and Mood Instability should certainly not be reified. The data and clinical experience suggest that Mood Instability is a necessary descriptor of disordered depressed mood. Consequently, we recommend that specific questions about Mood Instability be incorporated into clinical and research interviews, and also into criteria for the depressive syndrome. This could lead to improved treatment results [46], more accurate suicide assessment [47], and more progress in developing new causal hypotheses [19] and would be more compatible with a model of mood disorders as chronic complex disorders [48]. There are limitations to our argument based on the studies. In Studies 1 and 2, the measures of Mood Instability (EPI-N Mood Instability factor and ALS) are retrospective scales and liable to recall bias but they do focus attention on Mood Instability. The clinical samples in studies 2 and 3 are from one centre. This paper addresses the relationship of Mood Instability with depression assessed as a summation of symptoms; future studies might also include diagnostic assessments.
Conclusions Traditional depression diagnostic criteria and questionnaires are limited because inquiry about Mood Instability has been omitted. We propose that measures of Mood Instability should be added to clinical and research interviews. This could enhance the search for causes of mood disorders and their treatment, but the proof would lie in the research results.
Conflict of interest statement There are no potential conflicts of interest to declare.
Acknowledgement This research was supported by the Department of Psychiatry. Mr. Y. Yang and Mr. A. Houmphan were supported by funding from the Dean of Medicine.
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