Department of Psychiatry, University of Birmingham, Queen Elizabeth Psychiatric Hospital, Birmingham;
Division of Psychological Medicine, Institute of Psychiatry, London;
Department of Psychiatry, University of Birmingham, Queen Elizabeth Psychiatric Hospital;
Department of Psychiatry, University of Birmingham, Queen Elizabeth Psychiatric Hospital, and Department of Psychological Medicine, University of Wales College of Medicine, Cardiff;
Department of Psychiatry, University of Birmingham, Queen Elizabeth Psychiatric Hospital;
Department of Psychiatry, University of Birmingham, Queen Elizabeth Psychiatric Hospital, and Department of Psychological Medicine, University of Wales College of Medicine, Cardiff;
Department of Psychiatry, University of Birmingham, Queen Elizabeth Psychiatric Hospital;
SGDP Research Centre, Institute of Psychiatry, London;
Department of Psychiatry, University of Birmingham, Queen Elizabeth Psychiatric Hospital, and Department of Psychological Medicine, University of Wales College of Medicine, Cardiff;
Department of Psychiatry, University of Birmingham, Queen Elizabeth Psychiatric Hospital, and Department of Psychological Medicine, University of Wales College of Medicine, Cardiff, UK
Correspondence: Dr Lisa Jones, Department of Psychiatry, Division of Neuroscience, University of Birmingham, Queen Elizabeth Psychiatric Hospital, Birmingham B15 2QZ, UK. Tel: +44 121 678 2362; fax: +44 121 678 2351; e-mail: l.a.jones{at}bham.ac.uk
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ABSTRACT |
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Aims To compare cognitive style in people with affective disorders and in healthy controls.
Method Self-rated questionnaires were administered to 118 individuals with bipolar I disorder, 265 with unipolar major recurrent depression and 268 healthy controls. Those with affective disorder were also interviewed using the Schedules for Clinical Assessment in Neuropsychiatry and case notes were reviewed.
Results Those with bipolar disorder and those with unipolar depression demonstrated different patterns of cognitive style from controls; negative self-esteem best discriminated between those with affective disorders and controls; measures of cognitive style were substantially affected by current levels of depressive symptomatology; patterns of cognitive style were similar in bipolar and unipolar disorder when current mental state was taken into account.
Conclusions Those with affective disorder significantly differed from controls on measures of cognitive style but there were no differences between unipolar and bipolar disorders when current mental state was taken into account.
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INTRODUCTION |
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METHOD |
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Individuals were included if they met the following criteria:
Individuals were excluded if they:
Of those suitable individuals identified via our systematic screening procedure, 44.0% refused to participate and we were unable to make contact with a further 13.9%. Of those who agreed or volunteered to take part, 9.4% failed to complete the questionnaires. Our final sample comprised 118 individuals with bipolar I disorder (47.5% recruited systematically) and 265 with unipolar major recurrent depression (39.2% recruited systematically).
The controls were a sub-sample of participants who had originally been recruited to the GENESiS (Genetic and Environmental Nature of Emotional States in Siblings) study (Sham et al, 2000). This study recruited 34 371 individuals from general practices in England and Wales. Index individuals were registered with these practices, were aged between 18 and 55 years and had no current serious medical illness or disability. GENESiS participants were approached to take part in the current study if they fell into the bottom 20% of the distribution on the Sham Composite Index of Liability to Depression and Anxiety (G; Sham et al, 2000). G comprises responses to the following self-report measures: General Health Questionnaire (GHQ12, 12-item version; Goldberg et al, 1997); short form of the neuroticism sub-scale of the Eysenck Personality Questionnaire (EPQN; Eysenck & Eysenck, 1975); and two sub-scales of the Mood and Anxiety Symptoms Questionnaire (MASQ; Watson et al, 1995) which measure levels of anxious arousal (MASQAA) and high positive affect (MASQHPA).
Controls were screened for a personal or family history of psychiatric illness using a semi-structured telephone interview. Of those controls who agreed to take part in the study, 3.9% failed to complete the questionnaires. Our final control sample comprised 268 individuals.
Basic demographic and clinical features of the samples are presented in Tables 1 and 2.
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Assessments
Those with affective disorders were interviewed using the Schedules for
Clinical Assessment in Neuropsychiatry (SCAN;
Wing et al, 1990) and
psychiatric/general practice case notes were reviewed. These data were
combined for each participant to form a written case vignette. Best-estimate
lifetime diagnoses were made according to DSMIVTR, ICD10
and RDC. The vignettes were also used to rate other key clinical variables
(such as age at onset and number of episodes of illness). Each individual was
diagnosed and had key clinical variables rated independently by at least two
members of the research team, and consensus was reached. Inter-rater
reliability was high. This was formally assessed using 20 cases and resulted
in mean kappa statistics of 0.85, 0.83 and 0.80 for DSMIVTR,
ICD10 and RDC diagnoses, respectively. Mean kappa statistics for other
key clinical variables ranged from 0.81 to 0.99. Mean intraclass correlation
coefficients for other key clinical variables ranged from 0.91 to 0.97.
The following self-rated questionnaires, all with demonstrated validity and reliability, were part of a larger pack of questionnaires administered to the groups with affective disorders and the controls.
Rosenberg Self-Esteem Questionnaire
The Rosenberg Self-Esteem Questionnaire (SEQ;
Rosenberg, 1965) measures
trait self-esteem. It is a ten-item questionnaire comprising five positive
statements (e.g. On the whole I am satisfied with myself) and
five negative statements (e.g. At times I think I am no good at
all). We used the version in which each item is rated on a 14
scale (from strongly disagree to strongly agree for the positive items and
strongly agree to strongly disagree for the negative items). Thus, scores can
range from 5 to 20 on both sub-scales, with high scores on the positive
sub-scale reflecting high positive self-esteem and high scores on the negative
sub-scale reflecting low negative self-esteem. Combining these sub-scales
produces a total SEQ score which can range from 10 to 40, with higher total
scores reflecting higher total self-esteem.
Dysfunctional Attitudes Scale
The Dysfunctional Attitudes Scale (DAS) measures underlying beliefs and
attitudes. We used the 24-item version of the DAS
(Power et al, 1994).
Each item is rated on a 17 scale (totally disagree to totally agree,
except for three items where the scoring is reversed). As well as a total
score, which can range from 24 to 168, the DAS gives three sub-scale scores,
each ranging from 8 to 56. The three sub-scales are achievement (example item:
If I fail partly, it is as bad as being a complete failure),
dependency (example item: If others dislike you, you cannot be
happy) and self-control (I should always have complete control
over my feelings).
Altman Self-Rating Mania Scale
The Altman Self-Rating Mania Scale (ASRM;
Altman et al, 1997)
assesses the presence and/or severity of current manic symptoms. It comprises
five items scored from 0 (absent) to 4 (present to a severe degree). Total
scores range from 0 to 20.
Beck Depression Inventory
The Beck Depression Inventory (BDI; Beck
& Steer, 1987) assesses the presence and/or severity of
current depressive symptoms. It comprises 21 items scored from 0 (absent) to 3
(present to a severe degree). Total scores range from 0 to 63.
Eysenck Personality Questionnaire
We used the 90-item version of the Eysenck Personality Questionnaire (EPQ;
Eysenck & Eysenck, 1975).
Each item is rated either yes or no by
respondents. The EPQ gives scores for three personality dimensions:
extraversion, neuroticism (EPQN) and psychoticism. Scores for the
EPQN range from 0 to 23.
Procedure
Individuals were approached to participate in the study when they were
judged by the treating medical team to be in a euthymic state. After the
semi-structured interview, the questionnaires were left with participants to
rate and return to the team (stamped, addressed return envelopes were
provided). They were given written instructions to complete all of the
questionnaires at the same time within 1 week of receiving them. If
the questionnaires were not returned after 1 month, a reminder letter was sent
with another copy of the questionnaires and a return envelope. If the
questionnaires were still not returned after a further 2 weeks, a reminder
telephone call was made.
Controls received the questionnaires via the post. Otherwise the procedure was identical to that outlined above.
This study received all necessary multi-region and local research ethics committee approval.
Statistical analysis
The three groups were compared for socio-demographic variables using the
2-test or one-way analysis of variance (ANOVA), followed by
post hoc comparisons using the Tukey test. Differences in key
clinical variables between those with bipolar I disorder and those with
unipolar major recurrent depression were examined using independent sample
t-tests or
2-tests.
The distributions of the questionnaire scores in each of the groups approximated normal, thus the three groups were compared on the ASRM, BDI and all cognitive style measures using univariate one-way ANOVAs, followed by the Tukey test. Two-way univariate analyses of covariance (ANCOVAs) were then carried out with group and gender as factors and age, ASRM and BDI scores (both separately and together) as covariates.
Binary logistic regression using forward stepwise likelihood ratio for variable selection was carried out to determine the best predictors of affective disorder versus control status. Stepwise linear multiple regression was used to examine which cognitive style variables best predicted EPQN score in those with affective disorders.
The Spearman rank correlation coefficient was used to examine the correlations between the cognitive style variables and key measures of past psychiatric history in those with affective disorders.
All analyses were undertaken using the Statistical Package for the Social Sciences for Windows (version 10.0.7).
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RESULTS |
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Clinical features of those with affective disorders are summarised in Table 2. Age at illness onset, defined as age at first clinically significant functional impairment due to affective illness, was similar for the two groups. Those with bipolar I disorder had significantly more episodes of illness and significantly more psychiatric hospital admissions than those with unipolar major recurrent depression. Nearly three-quarters of those with bipolar I disorder (n=86) had experienced psychosis compared with approximately 8% (n=21) of those with unipolar major recurrent depression.
Comparison of cognitive style between the groups
Mean scores for each of the groups on each of the cognitive style measures
are presented in Table 3. There
were statistically significant differences between groups on all measures. Not
only did those with affective disorders differ from controls but they also
showed a significantly different pattern of results. Those with unipolar major
recurrent depression showed the lowest levels of self-esteem (low positive and
high negative self-esteem) and those with bipolar I disorder scored
significantly lower than controls and higher than those with major recurrent
depression. Those with major recurrent depression also showed the highest
level of dysfunctional attitudes, followed by those with bipolar I disorder,
followed by controls. This pattern was true for each of the sub-scales of the
DAS.
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These data were further analysed using ANCOVA. No significant gender by group interactions were observed, and controlling for age and ASRM scores (both separately and together) did not alter the findings. When current levels of depression, as measured by the BDI, were taken into account, no differences between the two groups with affective disorders on any of the measures emerged. However, both groups still exhibited lower levels of self-esteem and more dysfunctional attitudes (total score and achievement and dependency sub-scales) than controls. Those with major recurrent depression scored significantly higher than controls on the DAS self-control sub-scale, and those with bipolar I disorder were not significantly different from those with major recurrent depression or controls. These analyses were repeated using only those who had been recruited systematically (56 with bipolar I disorder and 104 with unipolar major recurrent depression) and an identical pattern of results emerged.
Logistic regression was carried out to determine which combination of cognitive style variables best predicted group membership (i.e. control or affective disorder). Gender, age, BDI scores, ASRM scores and all cognitive style measures were entered into the regression. The best solution correctly classified 86.3% of participants. The significant variables in this solution were BDI (OR=1.23, 95% CI 1.151.31, P<0.0001) and SEQ negative sub-scale (OR=0.68, 95% CI 0.620.75, P<0.0001).
EPQ neuroticism in those with affective disorders
In order to explore how cognitive style related to more widely used
concepts of personality and vulnerability to mood disturbance, we undertook a
multiple linear regression analysis in those with affective disorders with
EPQN as the dependent variable. After controlling for BDI score, the
following cognitive style variables predicted 49.5% of the variance in
EPQN: SEQ total score (standardised ß=0.34,
P<0.0001) and DAS achievement score (standardised ß=0.20,
P<0.0001). These two cognitive style variables and EPQN
were also significantly correlated with age at illness onset (SEQ total
r=0.13, P=0.02; DAS achievement r=0.13,
P=0.01; EPQN r=0.12, P=0.02). SEQ
total score and EPQN were significantly correlated with number of
previous episodes of depression (r=0.13, P=0.01;
r=0.17, P=0.001, respectively).
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DISCUSSION |
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Those participating in this study were: (a) narrowly defined they met lifetime diagnostic criteria according to three widely used psychiatric classification systems; (b) well characterised illness data were collected using a validated semi-structured interview and case note review, and a range of clinical variables were rated using the consensus method, with excellent interrater reliability; (c) representative a large percentage were systematically recruited. The controls were unaffected and selected for a low risk of developing a mood disorder. This study builds on previous work in this area which has tended to use small, selective samples and has shown inconsistent results.
Comparison of those with mood disorders and healthy controls
We have shown lower self-esteem (greater negative evaluation of self and
less positive evaluation of self) and more dysfunctional attitudes (greater
need for achievement, greater dependency on others and greater need for
control of self) among those with bipolar and unipolar disorders compared with
healthy controls. Our finding of abnormalities of cognitive style in those
with mood disorders supports previously published work
(Scott et al, 2000).
We have demonstrated that when possible confounding factors are controlled
for, the best predictor of whether a participant has a mood disorder or is a
healthy control is the score on the negative sub-scale of the SEQ. It is
interesting to note that Scott & Pope
(2003) showed that negative
self-esteem was the most robust predictor of both manic and depressive relapse
in those with bipolar disorder. This sub-scale should be a target for future
research into cognitive style in affective disorders.
Importance of measuring current mental state
Our data show that it is essential to take account of current mental state
when investigating aspects of underlying cognitive style in individuals with
mood disorders. Although participants were studied when, in the opinion of the
responsible medical team, they were clinically euthymic, we found significant
levels of depressive symptoms. When we controlled for this in our analyses,
the pattern of findings was considerably altered. This supports previous work
that has demonstrated confounding effects of residual affective symptoms in
those with mood disorders on measures of cognitive style and
neuropsychological functioning (Ferrier
et al, 1999; Clark
et al, 2002; Farmer,
2004). However, it is important to note that a 12-year follow-up
of over 100 individuals with bipolar disorder demonstrated that sub-syndromal
and syndromal symptoms of depression were present for nearly 50% of the time,
suggesting that this characterises the usual mental state of
many individuals with bipolar disorder
(Judd et al, 2002). Those with unipolar and bipolar disorders with persistent residual symptoms
and the associated abnormalities of cognitive style are particularly at risk
of further relapse (Paykel et al,
1995; Scott & Pope,
2003).
Comparison of bipolar disorder with unipolar major recurrent depression
When current mental state is taken into account, the measures of cognitive
style employed in this study do not differentiate individuals who experience
episodes of mania from those with unipolar depression. We have not shown a
pattern of cognitive style that is unique to individuals with bipolar
disorder. The measures we have included indicate a non-specific, generalised
pattern associated with mood disorders or psychiatric ill health in general.
These findings reflect previous studies in smaller or mixed clinical and
non-clinical samples that have shown similar patterns in both illnesses
(Ashworth et al, 1982;
Rosenfarb et al,
1998; Alloy et al,
1999; Scott & Pope,
2003; Lam et al,
2004), and studies which have demonstrated abnormal scores on
measures of cognitive style in individuals with other mental disorders, such
as schizophrenia (Hollon et al,
1986; Van Os & Jones,
2001). Much of the previous work on cognitive changes in bipolar
disorder has focused on information-processing systems
(Taylor Tavares et al,
2003). It is interesting to note that the majority of studies have
shown overlapping deficits in bipolar and unipolar disorder
(Bearden et al, 2001).
It is difficult to find a valid explanation of how shared beliefs across mood
disorders increase the risk of depressive relapse in one group but of manic
and depressive episodes in the other. Scott and others have hypothesised that
individuals with bipolar disorders show greater day-to-day variability in
cognitive style and have a self-esteem that is more vulnerable to shift in
response to external events. Such differences may emerge when cognitive style
is measured in a prospective longitudinal study, and are less likely to be
apparent in cross-sectional studies
(Scott, 2004).
Implications of the findings
The investigation of cognitive style in bipolar disorder is of clinical
relevance. For example, such factors could influence the development of
psychotherapies specific to the illness, likely adherence and response to
medication regimens and prognosis. We have shown that, independent of current
levels of symptoms, those with bipolar disorder show a fragile cognitive style
similar to those with unipolar depression. Therefore, it is not surprising
that psychological treatments that are effective in depression are also
helpful in reducing symptoms, improving global functioning and reducing
relapse in bipolar disorder (Scott et
al, 2001). Other aspects of cognition should be further
investigated in bipolar disorder to refine psychological models for the
development of specific targeted psychotherapies.
Neuroticism and cognitive style
We were interested to examine the relationship between measures of
cognitive style and EPQN in those with affective disorders. The concept
of neuroticism fell out of favour for some time, but Martin
(1985) described it in a
clinically meaningful way, namely as a marker of vulnerability to depression
and of a vulnerable cognitive style (fragile self-esteem, high levels of trait
dysfunctional beliefs). This relationship between neuroticism and cognitive
style appears to hold true for those with unipolar and bipolar disorder and
also was related, albeit modestly, to key measures of past psychiatric
history, such as number of previous episodes of depression and age at illness
onset. However, the nature of our control group (i.e. they were selected
partially on the basis of having low EPQN scores) means that we cannot
explore the relationship between cognitive style and neuroticism across groups
who have normal as compared with abnormal variability in mood states.
Limitations
Our study cannot determine whether the differences in cognitive style
observed in those with mood disorders are a cause or a consequence of the
onset or course of affective illness. It has generally been accepted that the
personality trait EPQN, for example, is genetically determined and
underlies vulnerability to develop unipolar depression
(Duggan et al, 1995;
Fanous et al, 2002). However, other authors (Farmer et
al, 2002) have argued that elevated EPQN in depression
may merely reflect residual symptoms. Prospective longitudinal studies which
begin in the premorbid state (e.g. using high-risk samples) are essential if
we are to understand the role of cognitive style in the development of
affective disorders. If aspects of cognition are shown to be markers of
underlying liability to bipolar disorder, they could be useful in aetiological
research, such as molecular genetic studies, and early intervention
studies.
A possible limitation of our study is that we have included individuals recruited systematically (via community mental health teams and lithium clinics) and opportunistically (via advertisements). However, the analysis was repeated using only those recruited using systematic methods, and the pattern of findings was unchanged.
To maximise our power to detect differences, we used a control group selected for low risk of developing a mood disorder (supernormal controls). The measures of cognitive style examined here, however, were not used to define the control group, and it is unlikely that the differences are accounted for merely by the selection of controls. Future research should aim to use unselected controls.
Our assessment tools can also be criticised. We used self-report measures of cognitive style and single subjective ratings of current manic and depressive symptoms, rather than combining them with objective investigator-rated scales. There is evidence that self-esteem in individuals with bipolar disorder is better measured by implicit means (Lyon et al, 1999) and that these individuals may show social conformism (Pardoen et al, 1993), which could bias self-report measures. However, we did not observe a significant difference between our three groups on the lie scale of the EPQ (data not shown).
In this study we have investigated only limited aspects of cognitive style in those with bipolar disorder. We have shown that although they exhibit abnormal patterns, these are not unique when compared with individuals with other mood disorders. Future studies of large, unselected samples of individuals with bipolar disorder with appropriate psychiatric and non-psychiatric controls could focus on other potentially interesting aspects of cognitive style, such as attributions, self-representations, novelty seeking traits, affective temperaments and perfectionism.
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Clinical Implications and Limitations |
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LIMITATIONS
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ACKNOWLEDGMENTS |
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Received for publication July 30, 2004. Revision received February 8, 2005. Accepted for publication February 12, 2005.
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