Division of Psychiatry
Unit of Paediatric and Perinatal Epidemiology, Division of Child Health
Division of Psychiatry
Unit of Paediatric and Perinatal Epidemiology, Division of Child Health, University of Bristol, Bristol, UK
on behalf of the ALSPAC study team
Correspondence: Dr Jonathan Evans, Division of Psychiatry, University of Bristol, Cotham House, Cotham Hill, Bristol BS6 6JL, UK.Tel: 0117 954 6666; fax: 0117 954 6672; e-mail: j.evans{at}bristol.ac.uk
Declaration of interest J.E. has received fees for lecturing from several pharmaceutical companies that market antidepressant medication.
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ABSTRACT |
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Aims To test whether those with negative self-schemas were at risk of onset of depression.
Method Data were collected by postal questionnaire from 12 003 women recruited during early pregnancy; questionnaires included measures of depressive symptoms and negative self-schemas. Regular questionnaires were sent during pregnancy and following childbirth.
Results Of 8540 women not depressed when recruited, 8.6% (95% CI 8.09.2) became depressed 14 weeks later. Those in the highesttertile for negative self-schema score were more likely to become depressed than those in the lowesttertile (odds ratio 3.04, 95% CI 2.483.73). The association remained after adjustment for baseline depressive symptoms and previous depression (OR 1.6, 95% CI1.272.02) and was of similar magnitude for onset 3 years later.
Conclusions Holding a negative self-schema is an independent risk factor for the onset of depression in women. This finding supports a key element of Becks cognitive theory. Understanding more about how negative self-schemas arise should help inform preventive policies.
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INTRODUCTION |
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METHOD |
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Participants completed the Edinburgh Postnatal Depression Scale (EPDS; Murray & Cox, 1990) as part of a series of postal questionnaires. This scale focuses on the cognitive and affective features of depression rather than somatic symptoms; although it was developed to screen for depression in women following childbirth, it is also useful in women outside the postnatal period (Cox et al, 1996), and is the only self-administered scale to have been validated for use both postnatally and during pregnancy (Murray & Cox, 1990). The scale can be used either as a continuous score or, when the score exceeds 12, to define a case of depression. A sensitivity of 86% and specificity of 78% when compared with a semi-structured diagnostic interview has been reported in ALSPAC (Thorpe, 1993). There is a close relationship between changes in the proportion reaching case definitions and mean score in populations, so categorical or continuous approaches to analysis of data such as these can be used interchangeably (Anderson et al, 1993). As questionnaires were not completed precisely at 18 weeks and 32 weeks of pregnancy, we excluded data from participants who returned the questionnaires less than 8 weeks apart. We included an adjustment for the time between questionnaires in the analyses. Incorporated in the postal questionnaire were three of the six sub-scales of the CrownCrisp Experiential Index, a validated self-rating inventory (Crisp et al, 1978); these sub-scales measured free-floating anxiety, depression and somatic anxiety. In this sample the internal consistency of these items exceeded 0.8.
The Interpersonal Sensitivity Measure (Boyce & Parker, 1989) was included with the postal questionnaires on a single occasion, at 18 weeks of pregnancy. This was devised to investigate vulnerability to depression, and includes items relating to negative beliefs about the self. We selected a priori items from this measure that we judged to measure negative self-schemas; G.L. and J.E. chose these items independently and differences were resolved at a consensus meeting. We excluded all items that included words related to mood, such as worry or feel, as these were most likely to be confounded by current mood state. Six of the 36 items were selected in this way (see Table 1). These items relate to Becks sociotropic schematic subtype, those who value closeness and security in relationships (Beck, 1983). Each item is rated on a four-point Likert scale: very like me, moderately like me, moderately unlike me and very unlike me (Boyce & Parker, 1989). We summed the scores from the six items to produce a total negative self-schema score that could range between 0 and 18 for each participant. We assessed internal consistency of these items by calculating Cronbachs alpha coefficient. For this we included all those who had completed the six items, whether depressed or not at 18 weeks of pregnancy. We used the derived negative self-schema scale score as the main explanatory variable, and grouped the women into tertiles based on their score on this measure.
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Statistical methods
For the main analyses using these prospective data we selected only women
who were not depressed (defined as an EPDS score below 13) at 18 weeks of
pregnancy. We investigated the onset of depression 14 weeks later, when the
women completed the EPDS again at 32 weeks of pregnancy. Onset of depression
was defined as a non-case score at 18 weeks of pregnancy becoming a case score
at 32 weeks of pregnancy. This definition missed those with onset and recovery
of depression between the two measurement times, but we do not consider that
this introduced a serious bias, as longer-duration illness would still have
been detected.
We used logistic regression analyses to investigate the association between the total score from the negative self-schema scale grouped in tertiles and onset of depression by 32 weeks of pregnancy. We adjusted for EPDS score at baseline and then adjusted for the potential confounding factors shown in Table 2 and also time between measures. These variables were all collected from the self-report postal questionnaires completed by the women at recruitment. As there were more missing data on maternal and paternal history of depression than for other variables we included a missing category as a dummy variable in the multivariable analysis for these two variables. As any association could have been due to residual confounding by current mood state, we repeated the analyses with additional adjustment for total score on the CrownCrisp index, thus attempting to remove the confounding effect of symptoms of both anxiety and depression. We repeated the analyses with depression as a continuous outcome, including all participants whether depressed or not at 18 weeks of pregnancy. This method of analysis produced very similar results and did not alter our conclusions, so for simplicity these results are omitted (further details available from the author upon request). Finally, we tested the stability of negative self-schema in predicting onset of depression over time. We selected women who were not depressed at 18 weeks of pregnancy and investigated the association between negative self-schemas and the onset of postnatal depression at 8 weeks, 8 months, 21 months and 33 months after childbirth.
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RESULTS |
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Comparison of participants scoring in the highest tertile on the six items of the Interpersonal Sensitivity Measure with those in the lowest two tertiles (combined) is shown in Table 2. High scorers were more likely to have higher EPDS scores, children, a family history of depression and a previous history of severe depression, and were older. The risk of depression onset increased with each unit increase in negative self-schema score (OR=1.16, 95% CI 1.141.19; P<0.001). Adjusting for EPDS depression score at baseline attenuated the association (OR=1.07, 95% CI 1.051.09; P<0.001), but it remained highly statistically significant. There was little further change when also adjusting for other potential confounders (OR=1.07, 95% CI 1.051.10; P<0.001, n=7845). To illustrate the size of the effect, a comparison of the proportion becoming depressed in each tertile for the negative self-schema score along with the odds ratios before and after adjustment are shown in Table 3.
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We stratified the analysis of the relationship between negative self-schema
and depression according to the baseline score on the EPDS. Although the
association of negative self-schema score was stronger at higher levels of
sub-threshold EPDS score, this interaction was not statistically significant
within the logistic regression model (likelihood ratio test, 2
0.05, d.f.=1, P=0.82). To test whether association was still present
in those with minimal baseline depressive symptoms, we repeated the analyses
for those women scoring 8 or below on the EPDS at baseline. The results were
similar although the association was weaker; the risk of depression onset
increased with each unit increase in negative self-schema score (OR=1.11, 95%
CI 1.071.15; P<0.001). Adjusting for EPDS depression score
at baseline attenuated the association (OR=1.06, 95% CI 1.021.10;
P<0.002), but it remained highly statistically significant. There
was little further change when also adjusting for other potential confounders
(OR=1.06, 95% CI 1.021.11; P=0.002, n=6104).
Additional adjustment for mood using the CrownCrisp index made no
substantial difference to the results: the adjusted odds ratio for onset of
depression for those in the highest tertile of the six-item negative
self-schema score was 1.42 (95% CI 1.111.80, P=0.008,
n=7540). As the requirement for complete data on these additional
measures meant a further 305 cases were excluded, we have not included these
results in this paper.
The size of the association between negative self-schema score at baseline (adjusted for baseline depression score) and the later onset of depression at 8 weeks, 8 months, 21 months and 32 months post-partum remained relatively constant. In comparison, the association between baseline depressive symptom score (adjusted for negative self-schema score at this time) and the later onset of depression diminished over time (Table 4).
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DISCUSSION |
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Methodological issues
This is a large, longitudinal study of women drawn from a representative
population with a relatively small proportion of missing data and extensive
data on potential confounders. These strengths increase the generalisability
of its findings. In this large study we were also able to adjust for a number
of confounding variables, the most important of which was the degree of mood
disturbance at baseline. The possibility of some residual confounding by mood
at the time of rating the cognitions can never be excluded, but the finding
that the increased risk associated with negative self-schemas was still
present 3 years later suggests that our scale was measuring a relatively
stable construct.
One limitation of the study is that we derived a measure of negative self-schemas from a questionnaire designed to measure personality in general, rather than cognitions specifically. However, negative self-schemas constitute one aspect of personality. The items selected are similar to items in the dysfunctional attitude scale relating to vulnerability and need for approval (Beck et al, 1991). The six items selected in this study in order to measure negative self-schemas concern the importance attached to other peoples opinions of the self; however, a number of potentially important dysfunctional beliefs were not included in the limited measure used in this study (Power et al, 1994). Another limitation is that there might have been some misclassification between cases and non-cases of depression, because we relied on a brief self-report scale for identifying depression rather than a more detailed, observer-rated measure. This misclassification would probably have been a source of random rather than systematic bias, and if anything should have reduced the strength of the association we found. We might also have misclassified individuals with onset of depression between 18 weeks and 32 weeks of pregnancy who have recovered by 32 weeks. Depression is rarely this short-lived and we would have included all the longer-duration episodes as cases. All women were under the potential stress of pregnancy and it is notable that there was a marked rise in self-reported depressive symptoms between the two measures. We have reported this finding previously, and we also found that depressive symptoms did not differ in other ways during pregnancy (Evans et al, 2001). It is possible to argue that these findings might not be generalisable to measuring negative self-schemas at other times, as the potential stress of pregnancy might be required to evoke them. This seems less likely because the association remained following adjustment for anxiety symptoms, but we cannot exclude this possibility.
Neuroticism and negative self-schemas
A number of studies have reported association between other aspects of
personality, such as interpersonal sensitivity or neuroticism, and the onset
of depression (Boyce et al,
1991; Kendler et al,
2002). Some argue that neuroticism can affect cognitions, and one
twin study reported that association between low self-esteem and vulnerability
to the onset of depression is largely explained by neuroticism
(Roberts & Kendler, 1999). It is possible that neuroticism is a vulnerability factor for developing
negative self-schemas, but we were unable to examine this relationship using
the ALSPAC data.
Cognitive vulnerability to depression
Negative self-schemas are to be distinguished from automatic negative
thoughts that arise during a period of depression. This distinction is
important if these negative self-schemas represent a true vulnerability to
depression rather than just state-dependent symptoms of a depressive
episode.
Other prospective studies have found no effect of negative self-schemas (Haaga et al, 1991; Lewinsohn et al, 2001), although one has reported an association with the onset of common mental disorder (Weich et al, 2003). These studies were too small to confidently exclude important association. The cognitive items selected for our study mostly referred to what the participant believed others thought or would think about her. It is likely that other schemas might be identified in large prospective studies that are associated with the onset of depression. Beck (1983) hypothesised that individuals who attach importance to independence, self-standards and achievement so-called autonomous individuals would also be prone to depression. Originally Beck suggested that negative self-schemas might be latent and therefore not directly accessible to questioning. This has been used to explain the negative findings of previous studies. Teasdale has suggested that these negative self-schemas are only evoked in response to a small drop in mood in those prone to depression (Teasdale, 1988). We found that negative self-schemas had an independent association with depression, but are much more common in those who also report depressive symptoms, consistent with Teasdales hypothesis. It is possible that using mood induction to elicit negative self-schemas (Kelvin et al, 1999) or measuring cognitions during natural mood fluctuations (Teasdale & Cox, 2001) would lead to an even stronger association between negative self-schemas and depression.
Implications
Our findings support the hypothesis that individuals who have negative
self-schemas are more vulnerable to developing depression. The origins of
these negative self-schemas have not been investigated. It is thought that
they might arise from adverse experiences, particularly during childhood when
social schemas relating to the self are first formed. Understanding how
individuals develop these negative self-schemas could lead to preventive
interventions that might reduce the population burden of depression.
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Clinical Implications and Limitations |
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LIMITATIONS
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ACKNOWLEDGMENTS |
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REFERENCES |
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Beck, A.T. (1967) Depression: Clinical, Experimental, and Theoretical Aspects. New York: Harper & Row.
Beck, A. T. (1983) Cognitive therapy of depression: new perspectives. InTreatment of Depression: Old Controversies and New Approaches (eds P. J. Clayton & J. E. Barrett), pp. 266278. New York: Raven Press.
Beck, A. T., Brown, G., Steer, R. A., et al (1991) Factor analysis of the Dysfunctional Attitude Scale in a clinical population. Psychological Assessment, 3, 478 483.[CrossRef]
Boyce, P. & Parker, G. (1989) Development of a scale to measure interpersonal sensitivity. Australian and New Zealand Journal of Psychiatry, 23, 341 351.[Medline]
Boyce, P., Parker, G., Barnett, B., et al (1991) Personality as a vulnerability factor to depression. British Journal of Psychiatry, 159, 106 114.[Abstract]
Cox, J. L., Chapman, G., Murray, D., et al (1996) Validation of the Edinburgh postnatal depression scale (EPDS) in non-postnatal women. Journal of Affective Disorders, 39, 185 189.[CrossRef][Medline]
Crisp, A. H., Jones, M. G. & Slater, P. (1978) The Middlesex Hospital Questionnaire: a validity study. British Journal of Medical Psychology, 51, 259 280.
Evans, J., Heron, J., Francomb, H., et al (2001) Cohort study of depressed mood during pregnancy and following childbirth. BMJ, 32, 257 260.
Haaga, D. A., Dyck, M. J. & Ernst, D. (1991) Empirical status of cognitive theory of depression. Psychological Bulletin, 110, 215 236.[CrossRef][Medline]
Kelvin, R. G., Goodyer, I. M., Teasdale, J. D., et al (1999) Latent negative self-schema and high emotionality in well adolescents at risk for psychopathology. Journal of Child Psychology and Psychiatry, 40, 959 968.[CrossRef]
Kendler, K. S., Gardner, C. O. & Prescott, C. A. (2002) Towards a comprehensive developmental model for major depression in women. American Journal of Psychiatry, 159, 1113 1145.
Lewinsohn, P. M., Joiner, T. E. & Rohde, P. (2001) Evaluation of cognitive diathesisstress models in predicting major depressive disorder in adolescents. Journal of Abnormal Psychology, 110, 203 215.[CrossRef][Medline]
Murray, D. & Cox, J. L. (1990) Screening for depression during pregnancy with the Edinburgh Postnatal Depression Scale (EPDS). Journal of Reproductive and Infant Psychology, 8, 99 107.
Power, M. J., Katz, R., McGuffin, P., et al (1994) The Dysfunctional Attitude Scale (DAS): a comparison of forms A and B and proposals for a new subscaled version. Journal of Research in Personality, 28, 263 276.[CrossRef]
Roberts, S. B. & Kendler, K. (1999) Neuroticism and self-esteem as indices of the vulnerability to major depression in women. Psychological Medicine, 29, 1101 1109.[CrossRef][Medline]
Scott, J., Williams, J. M. G., Brittlebank, A., et al (1995) The relationship between premorbid neuroticism, cognitive dysfunction and persistence of depression: a 1 year follow-up. Journal of Affective Disorders, 33, 167 172.[CrossRef][Medline]
Teasdale, J. D. (1988) Cognitive vulnerability to persistent depression. Cognition and Emotion, 2, 247 274.
Teasdale, J. D. & Cox, S. G. (2001) Dysphoria: self-devaluative and affective components in recovered depressed patients and never depressed controls. Psychological Medicine, 31, 1311 1316.[CrossRef][Medline]
Thorpe, K. (1993) A study of Edinburgh Postnatal Depression Scale for use with parent groups outside the postpartum period. Journal of Reproductive and Infant Psychology, 11, 119 125.
Weich, S., Churchill, R. & Lewis, G. (2003) Dysfunctional attitudes and the common mental disorders in primary care. Journal of Affective Disorders, 75, 269 278.[CrossRef][Medline]
Received for publication April 15, 2004. Revision received October 4, 2004. Accepted for publication October 9, 2004.