PHILIP D. SOMERVELL, JANE'I'q'E BEALS, J. DAVID KINZIE, JAMES BOEHNLEIN, PAUL LEUNG, AND SPERO M. MANSON
USE OF THE CES-D IN AN AMERICAN INDIAN VILLAGE
ABSTRACT. In this paper, we examine the performance of a pencil-and-paper screening questionnaire on depressive symptoms (the Center for Epidemiologic Studies Depression Scale, or CES-D) in a sample of 120 adult American Indians belonging to a single Northwest Coast tribe. Results of factor analyses suggest that somatic complaints and emotional distress are not well differentiated from each other in this population. CES-D scores (which have shown good sensitivity and specifity for depressive disorders in this sample) also show weak and apparently nonsignificant trends to be elevated in the presence of other psychiatric diagnoses (including alcoholism) or general impairment. However, because of the use of a convenience sample (rather than a probability sample), analyses of associations between study factors - including comorbidity - are liable to produce spurious results due to selection bias (including Berkson bias). On this basis, we suggest that the use of probability samples should assume a high priority in cross-cultural studies. The study of the entire population of interest is another solution to the sampling problem, particularly in small communities. This report examines the internal consistency and factor structure of the Center for Epidemiologic Studies Depression Scale, or CES-D, in a small Northwest Coast Indian community. We also examined the association of CESD scores with DSMIII-R diagnoses and with basic demographic variables. However, we encountered methodologic issues stemming from the sampling methods, which suggest treating findings regarding the relation between variables (in this dataset) with scepticism. These are problems which we believe to be important in all observational studies of psychiatric issues (and not only of psychiatric issues) in American Indian/Alaska Native communities.
METHODS Site
The data were collected in a coastal Indian village in the state of Washington. As of 1983, this village had 466 adult Indian residents, of whom 423 were members of one tribe; they belong to the Northwest Coast cultural group. In the twentieth century, the major economic activity has been forestry, with tourism and commercial fishing playing a lesser role. The reservation is relatively isolated; the nearest source for transportation by air, bus or truck is a town of approximately 17,000 which is 70 miles from the village along a slow, winding state highway. The participants in the current study are residents of the village, members of the predominant tribe, age 20 years or older. The data were collected in 1987-88 (Kinzie e t al. 1991). Culture, Medicine and Psychiatry 16: 503-517, 1993. © 1993 Kluwer Academic Publishers. Printed in the Netherlands.
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This was not a probability sample, but a convenience sample. For reasons unrelated to the analyses reported here, the sample included as many as possible of the surviving participants in an earlier study (Shore et aL 1973). In addition, other community members were recruited into the sample. Quota sampling was used in the latter effort, aiming at an overall sample with similar age and sex distribution to the community at large. Measures Center for Epidemiologic Studies Depression Scale (CES-D). The CES-D (Radloff 1977) was developed as a self-report, paper-and-pencil questionnaire to assess symptoms of depression. The instrument has limitations as a measure of DSMHI-R depressive disorders, since it differs from the latter in symptom coverage and time-referent. Nonetheless, the instrument is brief and well designed for self-report, which supports its usefulness for screening applications. Radloff (1977) found the internal consistency reliability of the CES-D to be high. Other investigators have reported high internal consistency reliabilities in Anglo, Black, Chicano and Chinese-American samples (Roberts 1980; Ying 1988). It has good ability to discriminate between community and patient samples, and moderate correlation with other scales related to affect (Radloff 1977). The correlation with clinician ratings of depression is fairly high among psychiatric inpatients and outpatients as well (Radloff 1977), and the scale differentiates between psychiatric patients with depression and those with other diagnoses (Weissman et al. 1977). The criterion validity of the CES-D has been assessed by several investigators. The work of Weissman et al. (1977) has shown that the scale is capable of detecting severe depressive symptomatology, even in the presence of other psychiatric disorders. In community samples, Myers and Weissman (1980) found a sensitivity of 63.6% and specificity of 93.9% when the usual cutpoint of 16 on CES-D scores was used. Using a cutpoint of 17, specificity was increased to 94.4% with no loss of sensitivity. Roberts and Vernon (1983) found somewhat lower levels of criterion validity for RDC major depression: sensitivity of 60% and specificity of 83.3%. Factor analyses of the CES-D have been performed by a number of investigators. In White samples, four factors have been distinguished (Radloff 1977; Roberts 1980); these have been described as I Depression, H Positive affect, III Somatic and retarded activity, IV Interpersonal. In fact, a similar factor structure has been reported in Blacks (Roberts 1980) and Hispanics (Roberts 1980; Golding & Aneshensel 1989). However, both Radloff and Roberts caution that distinctions between the factors should not be overemphasized, since the CES-D as a whole is highly internally consistent and the factors show moderate intercorrelations. This point of view is further supported by the work of
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Berkman et al. (1969) with persons aged 65 and over. Although both functional disability and age were correlated with CES-D scores, this was not due to the somatic CES-D items specifically but to all or nearly all items. A number of studies have suggested different factor structures among Latinos and Asian-Americans. Some of these find a structure in which the "somatic" and "depressed affect" factors of Radloff are combined into one (Ying 1988; Kuo 1984; Guarnaccia e t al. 1989), and two such factors could generally not be clearly distinguished from one another (Garcia & Marks 1989). Even in Roberts' 1980 report, the depressed affect and somatic symptom factors were correlated rather highly at r=.70. Only recently has the performance of the CES-D been investigated among American Indians or Alaska Natives. The instrument has shown good internal consistency reliability (Baron et al. 1990; Somervell et al. submitted). Among Indians, the samples investigated to date have suggested different factor structures for the CES-D than the four-factor structure described by Radloff and by Roberts. In the elder sample mentioned above, four factors were found, but Factor I included both somatic and affective items. In a boarding-school sample (92% of whom were from five Southeastern tribes), both a three-factor and a two-factor structure appeared acceptable; the two-factor solution collapsed the positive affect and somatic factors, which were distinct from one another in the three-factor model (Manson et al. 1990). Beals et al. (1991) and Keane e t al. (submitted) used confirmatory factor analyses, with samples of college students and of chronically ill elderly persons, respectively. In both these studies, three alternative models were tested, including Radloff's four-factor model, a threefactor model which combines the affective and somatic factors, and a singlefactor model. Both the four-factor and the three-factor models fit the data similarly and fit them better than the single-factor model. However, in both these investigations, the correlations between the affective and somatic factors were high (.90 and .94, respectively). The criterion validity of the CES-D has been studied in the same sample reported herein (Somervell et al. submitted); it showed criterion validity for depressive disorders which was comparable to that found in other ethnic groups (Myers & Weissman, 1980; Roberts & Vernon, 1983). While the CES-D does appear to measure depression, doubts have been raised as to whether it measures b o t h depression and anxiety together, or an even more general construct such as psychologic distress or demoralization (Frank 1974; Dohrenwend et al. 1978). Certainly the list of items does not coincide with the DSMI~-R criteria for major depression, and at least one item ("fearful") would fit with DSMIII-R anxiety disorders rather than mood disorders. In fact, Weissman e t al. (1977) found that CES-D scores showed moderate to high correlations with a variety of SCL-90 subscales, including anxiety, phobic anxiety, and paranoid ideation. Orme et al. (1986) found a fairly high correlation
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with trait anxiety, while Berkman et al. (1986) found that scores reflected the presence of chronic medical conditions as well as functional impairment apparently due to all or nearly all of the CES-D items. Similarly, Keane et al. (submitted) report an association between CES-D scores and self-perceived illhealth in a sample of older, chronically ill American Indians. The elevated CESD scores associated with a variety of psychiatric diagnoses, including alcohol abuse or dependence, may be explained by several mechanisms (Schuckit & Monteiro 1988). Alcohol use disorders and depressive disorders may have some causal relation to one another through biological or behavioral mechanisms. On the other hand, persons who have recently abused alcohol often experience anxious and depressive symptoms which may persist for weeks, apparently as a physiologic effect of alcohol withdrawal. In addition, depressive symptomatology may accompany psychiatric and non-psychiatric conditions (including alcoholism) as a result of functional impairment and problems of living, which in turn may be caused by the condition itself and/or by the social sequelae of psychiatric labelling. Frank (1974) and Dohrenwend et al. (1979) have discussed the concept of "demoralization," which may lead to help-seeking behavior and also may produce symptoms of anxiety and depression. The CES-D may be an indicator of demoralization, in addition to being sensitive to specific depressive syndromes. The Schedule for Affective Disorders and Schizophrenia, Lifetime Version (SADS-L) (Endicott & Spitzer, 1978). The SADS-L is a semi-structured diagnostic interview, designed to rule diagnoses in or out according to Research Diagnostic Criteria (Spitzer, Endicott & Robins 1978). For the current study, additional probes were added to ensure coverage of DSMIII-R criteria. In psychiatric inpatient samples, for scale scores derived from the interview, testretest reliabilities of .67-.78, internal consistencies of .58-.97 and intraclass reliabilities of .94-.99 were reported, except for formal thought disorder (Endicott & Spitzer, 1978). In a tribally heterogeneous sample of 10 American Indians, Shore et al. (1987) report very good interrater reliabilities (kappa coefficients ranging from .62 to 1.00). In the absence of any true "gold standard" for diagnosis, the SADS-L was chosen because it allows the use of clinical judgement in the use of probes and rapport-building (unlike a structured interview), while providing a guide which ensures coverage and notation of all pertinent symptoms (unlike a clinical psychiatric interview). It was felt that in the hands of a clinician well-trained in its use and familiar with the cultural group being studied, the SADS-L was a reasonable choice for gathering clinical psychiatric data. The Global Assessment of Functioning Scale (GAF). The GAF (American Psychiatric Association, 1987) is a revision of the Global Assessment Scale (Endicott et al. 1976) and the Children's Global Assessment Scale (Shaffer et al. 1983). It is a global assessment of psychological, social and occupational
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functioning according to clinical judgement. Ratings are made on a scale of 0-100. The scale has nine anchor points which are each described in a short paragraph. The scale is included in the DSMIII-R (American Psychiatric Association 1987) as an operationalization of Axis V. The Global Assessment Scale, which is very similar, has shown intraclass correlation coefficients of .69 to .91 (Endicott et al. 1976).
Procedure
Some subjects were interviewed in their homes, others in a room in the community health clinic. All interviews were conducted by one of four psychiatrists, including J.D.K., P.L. and J.B. All four had extensive cross-cultural experience, including experience working with American Indians. They were trained in the use of the SADS-L by an experienced SADS-L interviewer. After each SADS-L interview, the subject was asked to complete two self-report questionnaires, including the CES-D. Diagnostic procedures are described in detail elsewhere (Somervell et al. submitted). Data Analysis
For data analyses, both hand calculations and Statistical Analysis System (SAS) computer software were used. We have avoided the use of statistical significance testing, because of concerns about the appropriateness of such methods given the sampling problems to be discussed. Thus, in describing patterns of CES-D total score in subgroups of our sample, we display mean scores together with approximate 95% confidence intervals. The latter are meant for descriptive purposes only. CES-D total scores were calculated by the method described by Radloff (1977), weighting all items equally. Each item is so scored that a higher score indicates more symptomatology; the total is then the sum of all item scores. Where a particular item was not answered, the median score for that item was used. Confirmatory factor analyses were performed using the PRELIS and LISREL programs. Three factor structures were tested: a one-factor model, a four-factor model (Golding and Aneshensel 1989), and a three-factor model in which the "depressed affect" and "somatic" factors are collapsed (based on the work of Beals et al. 1991; Keane et al. submitted; and others). Both a covariance and a polychoric matrix were calculated, and the factor models were run for both. The results presented are based on the covariance input matrix. All diagnostic categories used in data analyses were based on the DSMIII-R consensus diagnoses (Somervell et al. submitted), for current diagnosis only.
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The Sample The sample interviewed with the SADS-L included 130 persons who were members of the dominant tribe. 121 of these (93%) filled out the CES-D. One subject had failed to answer nine of the twenty items of the CES-D and was therefore excluded; none of the other subjects had more than three missing values on CES-D items. The resulting sample consists of 120 persons (Table I). Eight persons (80%) of the ten who were not included in the CES-D sample had a psychiatric diagnosis, compared to 30% of the subjects who completed the CES-D. Their mean age was also greater (60.7 years in the non-responders, compared to 42.5 years for those who completed the CES-D). TABLE I Persons completing the CES-D: Descriptive Statistics
Sex
Age
Educa~on
Categories
N
Percent
Female Male 17-24 25-34 35---44 45-54 55-64 65-74 75-84 College graduate 1-3 years college High school graduate Partial high school 7-9 years Less than 7 years
64 56 14 31 22 24 16 10 3 7 32 40 25 14 1
53.3% 46.7% 11.7% 25.8% 18.3% 20.0% 13.3% 8.3% 2.5% 5.9% 26.9% 33.6% 21.0% 11.8% 0.8%
Performance of the CES-D CES-D scores ranged from 0 to 40 (the theoretically possible range is 0-60). 20.0% of the sample scored at or above the cutpoint of 16 (the cutpoint suggested by Radloff [1977], based on her sample, and commonly used in other studies as suggesting probable clinically significant depression). Cronbach's alpha for the CES-D total score was ~86. Confirmatory factor analyses suggested that the single-factor model clearly gave an inferior fit to the data. Both the fourfactor and the three-factor model gave good fit, with virtually no difference between them (Table II). Examination of the correlation coefficient between the
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CES-D IN AMERICAN INDIANS TABLE II Fits for covariance models, CES-D scores
NULL 1-FACTOR 3-FACTOR 4-FACTOR
X2
df
X2/df
GFI
BFI
995 396 272 272
190 170 167 164
5.23 2.33 1.63 1.66
0.757 0.817 0.819
0.68 0.85 0.84
Legend: GFI = Joreskog & Sorbom's goodness of fit index (Joreskog & Sorbom, 1989). NFI = Bentler & BoneR's Normed Fit Index (Bentler & Bonett, 1980).
TABLE III Correlations between CES-D factor scores Somatic/Affective Somatic/Affective Interpersonal 0.596 Positive --0.548
Interpersonal
-0.339
Positive
-
TABLE IV CESD: Three-factor model. Item loadings on each factor (with standard errors) Somatic/Affective Bothered Appetite Blues Mind Depressed Effort Failure Fearful Sleep Talk Lonely Cry Sad Getgoing
0.371 0.432 0.419 0.305 0.516 0.412 0.313 0.470 0.557 0.350 0.686 0.232 0.617 0.367
Positive Affect (0.076) (0.057) (0.055) (0.061) (0.059) (0.101) (0.066) (0.062) (0.076) (0.084) (0.069) (0.041) (0.064) (0.072)
Good Hopeful Happy Enjoy
0.305 0.484 0.758 0.663
Interpersonal (0.108) (0.095) (0.070) (0.064)
Unfriendly 0.411 (0.077) Dislike 0.605 (0.076)
depressed affect and somatic factors (.95 - Table III) suggested that the threefactor model was the most parsimonious. For this model, Chi-Square (167)=272, GFI=.817 (Table II). The items of the three factors, and their factor loadings, are shown in Table IV. "Crying spells" was the most problematic item; men, in particular, endorsed this symptom at only a very low level. Excluding it from the model would lead to a somewhat better fit. The three-factor model was chosen
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as the best, consistent with the conclusions o f several other investigators (Beals et al. 1991; Keane et al. submitted; Kuo 1984; Ying 1988; Guarnaccia et aL 1989). TABLE V CES-D total scores in demographic and clinical subgroups Group
N
Mean CES-D
56 64
10.2 9.0
12 15 17 75
17.6 12.8 I 1.7 7.2
53 44 23
8.1 10.0 12.3
7 4 11 84
23.6 11.8 9.1 7.4
+ 1.96 S.E.
Sex
Male Female GAF Score -71 Alcohol Never dependence/abuse Past dependence/abuse Current depend/abuse Current psychiatric diagnosis Any depression Any anxiety Alcohol dependence None
7.8, 12.6 7.0, 11.0 11.1, 6.9, 8.0, 5.8,
24.t 18.7 15.4 8.6
5.8, 10.4 7.7, 12.3 8.4, 16.2 14.5, 9.8, 5.2, 6.0,
32.8 13.8 13.0 8.8
Legend: "Any depression": Any depressive disorder, no alcohol dependence. "Any anxiety": Any anxiety disorder, no depressive disorder, no alcohol dependence. GAF: A score of 50 or less indicates "serious symptoms ... or any serious impairment in social, occupational, or school functioning (e.g., no friends, unable to keep a job)" (APA, 1987). A score of over 70 indicates no more than transient symptoms which are expectable reactions to psychosocial stressors; no more than slight impairment in functioning.
Associations o f CES-D Scores These relationships are presented descriptively in Table V. W e have not performed formal tests o f statistical significance, due to our concerns about the validity of such an analysis given the sampling methods used. However, Table V suggests that the differences if tested would not be statistically significant. CESD scores were slightly higher in men than in women, but showed no consistent trend with age. There was a tendency for persons with a current diagnosis of alcohol abuse or dependence to have higher scores than persons never having qualified for such a diagnosis. Persons with a past diagnosis had an intermediate mean score. Analyses using a different, exploratory, choice o f diagnostic categories showed a trend for subjects with depressive disorders to have higher C E S - D total scores than subjects in certain other diagnostic categories (who in turn had higher scores than those without any S A D S - L psychiatric diagnosis).
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However, the weakness of these trends, and the variability within each of the three groups, suggest that even if we had more confidence in the sampling methods, these patterns in the data would be suggestive at best. Mean scores also showed a weak trend to be inversely related to scores on the General Assessment of Functioning (GAF) scale; like the other patterns described, this would most likely not be statistically significant, judging from the amount of within-group variation. Examining the co-occurrence of SADS-L/DSMIII-R diagnoses, the odds ratio for the association of alcohol abuse or dependence and depressive disorders was 1.22. The 95% confidence limits (0.24, 6.32) on this odds ratio include 1.00, which is equivalent to a nonsignificant association. The same caveats as above apply to this analysis.
DISCUSSION Perhaps the first question to ask about any assessment tool is its acceptability. Ten of the 130 subjects who completed SADS-L interviews refused the CES-D. These ten subjects were older and more likely to have a psychiatric diagnosis than those who responded to the CES-D. The CES-D appears much less intrusive than the SADS-L interview as to its content, and is certainly much shorter. However, it is a self-report, paper-and-pencil questionnaire; perhaps this made it less acceptable (or less interesting) than the interview, which involved social interaction. However, it is also possible that by the end of the SADS-L interview, the respondents were simply tired or had reached the limits of their patience. In factor analyses, the high correlation between the depressed affect and the somatic distress factors suggested that they be collapsed into a single factor. The lack of a clear distinction between somatic and affective items is similar to what has been reported with some Asian-American and Latino samples. Western scientific culture tends to make a clear distinction between affective and psychological states, on the one hand, and bodily sensations on the other. This way of structuring experience and language is far from universal (Kleinman & Kleinman 1985). Rather, it has been pointed out that (for example) the "somatization" of depression is common and, in some populations, normative; a person may express severe depression in an idiom of physical distress, which in fact is how he/she perceives it (Katon et al. 1982). Our results support such an interpretation in this American Indian sample. However, it would be a mistake to overemphasize the differences between our sample and others in this respect. Even in white samples for which affective and somatic factors are more distinct, the internal consistency of the total CES-D score is approximately as high as in our sample and the four-factor scales are moderately intercorrelated.
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We report elsewhere (Somervell et aL submitted) that the use of factor scores (instead of total scores) did not enhance the specificity or sensitivity of the CESD. That suggests that while the factor scores represent more precisely defined clusters of symptoms than the total score, these clusters may not correspond well to the clinical construct of depressive disorders in this American Indian sample. In other words, the clustering of CES-D symptoms endorsed by these persons does not correspond well to the patterns of symptoms used by DSMIII-R to define depressive disorders. However, this interpretation must be tempered by the observation that subjects were not free to endorse any symptoms, but were constrained by the list of CES-D items. The CES-D provides only a limited selection of the DSMIII-R criterion symptoms of depressive disorders, and even the time-frame is different. Certain other patterns seen in the data are consistent with the notion that while CES-D scores discriminate persons with depressive disorders, they also reflect other psychiatric conditions and impairment in overall functioning. Persons with alcohol abuse or dependence diagnoses, as well as persons with other psychiatric diagnoses, tended to have lower scores than persons with depressive disorders, but somewhat higher scores than persons with no diagnosis. There was a consistent trend for lower GAF scores to be associated with higher CES-D scores. However, since the GAF is based partly on symptoms ascertained from other sources, this correspondence is to some extent to be expected. All of these patterns are at most suggestive, because they appear both weak and nonsignificant, and because of sampling issues to be discussed. One of our interests was in depressive symptomatology among persons with diagnoses of alcohol dependence or abuse. The comorbidity of affective disorders and alcohol use disorders is important because of its implications for treatment, and because of the difficulty of differential diagnosis of depressive symptoms in the presence of alcohol use disorders. It is worth nothing that the patterns seen in our sample, if considered descriptively and without regard for statistical significance, are broadly consistent with other reports on comorbidity: a positive (though very weak) relation between alcohol abuse/dependence and depressive disorders, as well as between alcohol abuse/dependence and depression symptom scores. However, for reasons having to do with the sampling design used in this study, we do not think that findings (whether positive or negative) on comorbidity are trustworthy in this study. This is why we have avoided tests of statistical significance. The sampling problem is nearly universal in studies of American Indian and Alaska Native populations, so we think it is worthy of detailed discussion. In general, when such studies have used general population samples at all, they have used samples of convenience. Typically, informants are asked to suggest other potential respondents, and networks of acquaintances are tapped. This runs counter to the mainstream of epidemiologic research, in which probability
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513
sampling is practically a sine qua non for any community-based observational study. A probability sample is one in which each person in the sampling frame (generally the population at large) has a known probability of being selected into the sample. It can be difficult to design a probability sampling scheme, and it can be a major undertaking to execute it. However, probably the major reason which has been cited for convenience sampling in studying Native communities is the concern that soliciting the participation of persons with whom the investigator is not acquainted may so offend them and the community as to jeopardize the researcher's access to that community. Since one cannot always count on wholehearted support from the entire community, and research is a sensitive issue among Native people, the risks are real. However, we will argue that in view of the limitations which the use of convenience samples imposes on the results, there is a need for a concerted effort to overcome these obstacles. It is a commonplace among epidemiologists and statisticians that sampling (or selection) patterns can invalidate the results of a study. There are two general issues here. First, all statistical methods are based on the assumption of probability sampling. Secondly, even in qualitative terms, if certain kinds of people are more likely than others to be in the sample, what is seen in that sample may be very misleading as an indication of what would be seen in the population at large. One example of this type of effect is of particular interest to those who study comorbidity. It appears to have first been discussed by Berkson (1946); the phenomenon has become known as Berkson's bias. The context was a type of study in which hospitalized patients were investigated to test the role of one disease as a cause of some other disease. Berkson showed that spurious results could be produced - e.g., an apparent association between the two diseases which did not reflect any such pattern in the general population - because of different prevalence rates for the two diseases in the general population, and different hospitalization rates for persons with the respective diseases. It is noteworthy that the concept of Berkson's bias deals only with the m a t h e m a t i c a l effect of overlapping prevalences and selection probabilities of individual disorders. It does not deal with the qualitative issue of the effects of symptomatology and impairment on people's behavior. Yet we should not find it surprising if, for subjective or behavioral reasons, people with more than one disorder have higher hospitalization rates than would be predicted based on the hospitalization rates for either disorder alone. Such an effect might then be a d d e d to that produced by Berkson's bias per se. The conditions under which Berkson's bias can occur have been further discussed by Boyd (1979) and by Roberts et al. (1978). Theoretically, it can either inflate or minimize the apparent associations between medical conditions, and in at least one large dataset it has been shown that this can indeed occur (Roberts et al. 1978). How does this pertain to the data which we have presented? In both a community-based study using a convenience sample and a hospital-based study,
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a person's likelihood of entering the sample is not random, and the factors influencing this likelihood are not only out of the investigator's control, but not fully ascertainable. In fact, where psychological issues are the subject of study, a person's likelihood of entering the study sample (selection rate) is likely to be correlated with some of the factors to be studied - just as hospitalization rates are related to which disease(s) a person suffers from. Psychiatric disorder and symptomatology may be reflected in personality style and social behavior (e.g., withdrawal versus gregariousness), extensiveness of social networks, and perceived approachability. These characteristics, in turn, may affect a person's probability of being in the sample. Since the prevalences of disorders and symptoms also differ, the conditions for Berkson's bias seem to be met. The conditions for other forms of bias based on behavior patterns (as mentioned earlier) exist as well. This pertains to any analyses of associations between different study factors. The objection may be raised that drawing a probability sample is of little use if (as often happens) a substantial proportion of subjects refuse to participate: refusal is not a random event, being correlated with demographic, health-related and behavioral factors. In fact, this is seen in our sample, where those subjects who refused the CES-D were older and more likely to have a diagnosis than those who consented. However, it is possible to assess the potential effects of refusals on the study results, and one can attempt to do something about it. One can estimate, using a range of assumptions about sampling rates and prevalences, how the results might hypothetically have been distorted. In the most favorable case, this might lead to the conclusion that the bias cannot have been severe. One can also devote ingenuity and effort to recruiting a random sample of the refusers (even if only to collect more limited data from them). One can use these special data from refusers to estimate how the research results might be different if they had participated in the study itself. With a convenience sample, none of this is possible. There is another alternative: to study the entire population of interest (e.g., all adults in the community). In most epidemiologic studies, the reason not to do so is that the numbers are too large - a reason which is not always compelling in a village (for example) of a few hundred persons. Here, the issue to be confronted is, rather, community acceptance of the research enterprise. In fact, Sampath (1974) used just such an approach in his study of an Eskimo village on Baffin Island (Canada). In non-Native populations, an example is provided by the Evans County Study (McDonough et al., 1963; Hames, 1971), conducted in a rural county in the state of Georgia. This approach will not always be practical. However, where it can be used, it will solve the scientific problem, and it may have the beneficial side-effect of forcing the research enterprise to be truly responsive to the concerns of the community.
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NOTE 1 The preparation of this manuscript was supported by NIMH Grant No. R03 MH45167--01A1 and NIMH Grant No. 5R01 MH42473. Drs. Somervell, Beals and Manson are located at the National Center for American Indian and Alaska Native Mental Health Research in the Department of Psychiatry, University of Colorado Health Sciences Center. Drs. Kinzie, Boehnlein and Leung are at the Department of Psychiatry, the Oregon Health Sciences University. Correspondence concerning this article should be sent to Philip D. Somervell, Ph.D., Department of Psychiatry, Campus Box C249-17, University of Colorado Health Sciences Center, Denver, Co 80262.
REFERENCES American Psychiatric Association 1987 Diagnostic and Statistical Manual of Mental Disorders. Washington, D.C.: American Psychiatric Association. Bar6n, A.E., S.M. Manson, L.M. Ackerson, and D.L. Brenneman 1990 Depressive Symptomatology in Older American Indians with Chronic Disease. In Screening for Depression in Primary Care. C. Attkisson, and J. Zich, ed. pp. 217-231. New York, NY: Routledge, Kane & Company. Beals, J., E.M. Keane, R.W. Dick, and S.M. Manson in press The Factorial Structure of the CES-D Among American Indian College Students. Psychological Assessment. Bentler, P. & D. Bonett 1980 Significance tests and goodness of fit in the analysis of covariance structures. Psychol Bull 88(3):588---606. Berkman, L.F., C.S. Berkman, S. Kasl, D.H.J. Freeman et al. 1986 Depressive Symptoms in Relation to Physical Health and Functioning in the Elderly. Am J Epidemiology 124(3):372-388. Berkson, J. 1946 Limitations of Application of Fourfold Table Analysis to Hospital Data. Biomet Bull 2:47-53. Boyd, A.V. 1979 Testing for Association of Diseases. J Chron Dis 32:667-672. Chance, N.A. 1962 Conceptual and Methodological Problems in Cross-Cultural Health Research. Am J of Public Health 52(3):410--417. Cole, P., and A. Morrison 1980 Basic Issues in Population Screening for Cancer. JNCI 61(5): 1263-1272. Dohrenwend, B.P., L. Oksenberg, and P. Shrout 1979 What Brief Psychiatric Screening Scales Measure. In National Center for Health Services Research Methods: Third Biennial Research Conference. DHHS Publication No. (PHS) 81-3268. pp. 188-198. U.S. Department of Health and Human Services. Endicott, J., and R.L. Spitzer 1978 A Diagnostic Interview: The Schedule for Affective Disorders and Schizophrenia. Arch Gen Psychiatry 35:837-844. Endicott, J., R.L. Spitzer, J.L. Fleiss, and J. Cohen 1976 The Global Assessment Scale: A procedure for measuring overall severity of psychiatric disturbance. Arch Gen Psychiatry 33:766-771. Frank, J. 1974 Persuasion and Healing. Baltimore, MD: Johns Hopkins University Press.
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Garcia, M., and G. Marks 1989 Depressive Symptomatology Among Mexican-American Adults: An Examination with the CES-D Scale. Psychiatry Research 27:137-148. Golding, J.M., and C.S. Aneshensel 1989 Factor Structure of the Center for Epidemiologic Studies Depression Scale Among Mexican Americans and Non-Hispanic Whites. Psychol Assessment 1(3): 163-168. Guarnaccia, P.J., R. Angel, and J.L. Worobey 1989 The Factor Structure of the CES-D in the Hispanic Health and Nutrition Examination Survey: The Influences of Ethnicity, Gender and Language. Soc Sci Med 29(1):85-94. Hames, C.G. 1971 Evans County Cardiovascular and Cerebrovascular Epidemiologic Study. Arch Intern Med 128:883-889, John C. Cassel, Guest Editor (Introduction). Joreskog, J., and D. Sorbom 1989 LISREL VII, A User's Guide. Scientific Press, Mooresville, Indiana. Katon, W., A. Kleinman, and G. Rosen 1982 Depression and Somatization. Am J Medicine 72(1): 127-135,241-247. Keane, E.M., J. Beals, R.W. Dick, and S.M. Manson submitted Self-perceived Health Status and the Factorial Structure of the CES-D among Chronically I11,Older American Indians. Kinzie, J.D., P.K. Leung, J. Boehnlein, D. Matsunage, R. Johnson in press Psychiatric Epidemiology of an Indian Village: A 19-year Replication Study. J Nerv Mental Disorders. Kleinman, A., and J. Kleinman 1985 Somatization: The Interconnections in Chinese Society Among Culture, Depressive Experiences, and the Meanings of Pain. In Culture and Depression: Studies in the Anthropology and Cross-Cultural Psychiatry of Affect and Disorder. A. Kleinman, and B. Good, (eds.), Berkeley, CA: University of California Press. Kuo, W. 1984 Prevalence of Depression Among Asian-Americans. J Nerv Ment Disorders 172(8):449--457. Leighton, A.H. 1959 My name is Legion. In The Stirling County Study. Basic Books. Manson, S.M., L.M. Ackerson, R.W. Dick, A.E. Baron, and C.M. Fleming 1990 Depressive Symptoms among American Indian Adolescents: Psychometric Characteristics of the CES-D. J Consult Clin Psychology 2:231-237. McDonough, J.R., C.G. Hames, S.C. Stulb, and G.E. Garrison 1963 Cardiovascular Disease Field Study in Evans County, GA: Characteristics of the Study Population. Public Health Reports 78(12): 1051-1058. Myers, J.K., and M.M. Weissman 1980 Use of a Self-Report Symptom Scale to Detect Depression in a Community Sample. Am J Psychiatry 137(9): 1081-1084. Ornae, J.G., J. Reis, and E.J. Herz 1986 Factorial and Discriminant Validity of the Center for Epidemiologic Studies Depression (CES-D) Scale. J Clin Psychology 42(1):28-33. Pollack, D., and J.H. Shore 1980 Validity of the MMPI with Native Americans. Am J Psychiatry 137(8):946-950. Radloff, L.S. 1977 The CES-D Scale: A Self-Report Depression Scale for Research in the General Population. Appl Psychol Meas 1(3):385-401. Roberts, R.E. 1980 Reliability of the CES-D Scale in Different Ethnic Contexts. Psychiatry
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Research 2:125-134. Roberts, R.E., and S.W. Vernon 1983 The Center for Epidemiologic Studies Depression Scale: Its Use in a Community Sample. Am J Psychiatry 140(1):41-46. Roberts, R., W.O. Spitzer, T. Delmore, and D.L. Sackett 1978 An Empirical Demonstration of Berkson's Bias. J Chron Dis 31:119-128. Rosner, B. 1982 Fundamentals of Biostatics. Boston, MA: DuxburyPress. Sampath, H.M. 1974 Prevalence of Psychiatric Disorders in a Southern Baffin Island Eskimo Settlement. Can Psychiatric Assoc J 19:363-367. Schuckit, M.A., and M. Monteiro 1988 Alcoholism, Anxiety and Depression. Br J Addiction 83:1373-1380. Shaffer, D., Gould, M.S., Brassic, J. 1983 Children's Global Assessment Scale (CGAS). Arch Gen Psychiatry: 1228-1231. Shore, J.H., J.D. Kinzie, J.L. Hampson, and E.M. Pattison 1973 Psychiatric Epidemiology of an Indian Village. Psychiatry 36:70-81. Somervell, P.D., J. Beals, J.D. Kinzie, J. Boehnlein, P. Leung, and S. M. Manson submitted Criterion Validity of the CES-D in an American Indian Sample. Spitzer, R.L., J. Endicott, and L. Robins 1978 Research Diagnostic Criteria: Rationale and Reliability. Arch Gen Psychiatry 35:773-782. Weissman, M.M., D. Sholomskas, M. Pottenger, B.A. Prusoff, and B.Z. Locke 1977 Assessing Depressive Symptoms in Five Psychiatric Populations: A Validation Study. Am J Epidemiology 106(3):203-214. Ying, Y. 1988 Depressive Symptomatology among Chinese-Americans as Measured by the CES-D. J Clinical Psychol 44(5):739-746.
National Center for American Indian and Alaska Native Mental Health Research Department of Psychiatry University of Colorado Health Sciences University Denver, Colorado 80262
USE OF THE CES-D IN AN AMERICAN INDIAN VILLAGE
ABSTRACT. In this paper, we examine the performance of a pencil-and-paper screening questionnaire on depressive symptoms (the Center for Epidemiologic Studies Depression Scale, or CES-D) in a sample of 120 adult American Indians belonging to a single Northwest Coast tribe. Results of factor analyses suggest that somatic complaints and emotional distress are not well differentiated from each other in this population. CES-D scores (which have shown good sensitivity and specifity for depressive disorders in this sample) also show weak and apparently nonsignificant trends to be elevated in the presence of other psychiatric diagnoses (including alcoholism) or general impairment. However, because of the use of a convenience sample (rather than a probability sample), analyses of associations between study factors - including comorbidity - are liable to produce spurious results due to selection bias (including Berkson bias). On this basis, we suggest that the use of probability samples should assume a high priority in cross-cultural studies. The study of the entire population of interest is another solution to the sampling problem, particularly in small communities. This report examines the internal consistency and factor structure of the Center for Epidemiologic Studies Depression Scale, or CES-D, in a small Northwest Coast Indian community. We also examined the association of CESD scores with DSMIII-R diagnoses and with basic demographic variables. However, we encountered methodologic issues stemming from the sampling methods, which suggest treating findings regarding the relation between variables (in this dataset) with scepticism. These are problems which we believe to be important in all observational studies of psychiatric issues (and not only of psychiatric issues) in American Indian/Alaska Native communities.
METHODS Site
The data were collected in a coastal Indian village in the state of Washington. As of 1983, this village had 466 adult Indian residents, of whom 423 were members of one tribe; they belong to the Northwest Coast cultural group. In the twentieth century, the major economic activity has been forestry, with tourism and commercial fishing playing a lesser role. The reservation is relatively isolated; the nearest source for transportation by air, bus or truck is a town of approximately 17,000 which is 70 miles from the village along a slow, winding state highway. The participants in the current study are residents of the village, members of the predominant tribe, age 20 years or older. The data were collected in 1987-88 (Kinzie e t al. 1991). Culture, Medicine and Psychiatry 16: 503-517, 1993. © 1993 Kluwer Academic Publishers. Printed in the Netherlands.
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This was not a probability sample, but a convenience sample. For reasons unrelated to the analyses reported here, the sample included as many as possible of the surviving participants in an earlier study (Shore et aL 1973). In addition, other community members were recruited into the sample. Quota sampling was used in the latter effort, aiming at an overall sample with similar age and sex distribution to the community at large. Measures Center for Epidemiologic Studies Depression Scale (CES-D). The CES-D (Radloff 1977) was developed as a self-report, paper-and-pencil questionnaire to assess symptoms of depression. The instrument has limitations as a measure of DSMHI-R depressive disorders, since it differs from the latter in symptom coverage and time-referent. Nonetheless, the instrument is brief and well designed for self-report, which supports its usefulness for screening applications. Radloff (1977) found the internal consistency reliability of the CES-D to be high. Other investigators have reported high internal consistency reliabilities in Anglo, Black, Chicano and Chinese-American samples (Roberts 1980; Ying 1988). It has good ability to discriminate between community and patient samples, and moderate correlation with other scales related to affect (Radloff 1977). The correlation with clinician ratings of depression is fairly high among psychiatric inpatients and outpatients as well (Radloff 1977), and the scale differentiates between psychiatric patients with depression and those with other diagnoses (Weissman et al. 1977). The criterion validity of the CES-D has been assessed by several investigators. The work of Weissman et al. (1977) has shown that the scale is capable of detecting severe depressive symptomatology, even in the presence of other psychiatric disorders. In community samples, Myers and Weissman (1980) found a sensitivity of 63.6% and specificity of 93.9% when the usual cutpoint of 16 on CES-D scores was used. Using a cutpoint of 17, specificity was increased to 94.4% with no loss of sensitivity. Roberts and Vernon (1983) found somewhat lower levels of criterion validity for RDC major depression: sensitivity of 60% and specificity of 83.3%. Factor analyses of the CES-D have been performed by a number of investigators. In White samples, four factors have been distinguished (Radloff 1977; Roberts 1980); these have been described as I Depression, H Positive affect, III Somatic and retarded activity, IV Interpersonal. In fact, a similar factor structure has been reported in Blacks (Roberts 1980) and Hispanics (Roberts 1980; Golding & Aneshensel 1989). However, both Radloff and Roberts caution that distinctions between the factors should not be overemphasized, since the CES-D as a whole is highly internally consistent and the factors show moderate intercorrelations. This point of view is further supported by the work of
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Berkman et al. (1969) with persons aged 65 and over. Although both functional disability and age were correlated with CES-D scores, this was not due to the somatic CES-D items specifically but to all or nearly all items. A number of studies have suggested different factor structures among Latinos and Asian-Americans. Some of these find a structure in which the "somatic" and "depressed affect" factors of Radloff are combined into one (Ying 1988; Kuo 1984; Guarnaccia e t al. 1989), and two such factors could generally not be clearly distinguished from one another (Garcia & Marks 1989). Even in Roberts' 1980 report, the depressed affect and somatic symptom factors were correlated rather highly at r=.70. Only recently has the performance of the CES-D been investigated among American Indians or Alaska Natives. The instrument has shown good internal consistency reliability (Baron et al. 1990; Somervell et al. submitted). Among Indians, the samples investigated to date have suggested different factor structures for the CES-D than the four-factor structure described by Radloff and by Roberts. In the elder sample mentioned above, four factors were found, but Factor I included both somatic and affective items. In a boarding-school sample (92% of whom were from five Southeastern tribes), both a three-factor and a two-factor structure appeared acceptable; the two-factor solution collapsed the positive affect and somatic factors, which were distinct from one another in the three-factor model (Manson et al. 1990). Beals et al. (1991) and Keane e t al. (submitted) used confirmatory factor analyses, with samples of college students and of chronically ill elderly persons, respectively. In both these studies, three alternative models were tested, including Radloff's four-factor model, a threefactor model which combines the affective and somatic factors, and a singlefactor model. Both the four-factor and the three-factor models fit the data similarly and fit them better than the single-factor model. However, in both these investigations, the correlations between the affective and somatic factors were high (.90 and .94, respectively). The criterion validity of the CES-D has been studied in the same sample reported herein (Somervell et al. submitted); it showed criterion validity for depressive disorders which was comparable to that found in other ethnic groups (Myers & Weissman, 1980; Roberts & Vernon, 1983). While the CES-D does appear to measure depression, doubts have been raised as to whether it measures b o t h depression and anxiety together, or an even more general construct such as psychologic distress or demoralization (Frank 1974; Dohrenwend et al. 1978). Certainly the list of items does not coincide with the DSMI~-R criteria for major depression, and at least one item ("fearful") would fit with DSMIII-R anxiety disorders rather than mood disorders. In fact, Weissman e t al. (1977) found that CES-D scores showed moderate to high correlations with a variety of SCL-90 subscales, including anxiety, phobic anxiety, and paranoid ideation. Orme et al. (1986) found a fairly high correlation
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with trait anxiety, while Berkman et al. (1986) found that scores reflected the presence of chronic medical conditions as well as functional impairment apparently due to all or nearly all of the CES-D items. Similarly, Keane et al. (submitted) report an association between CES-D scores and self-perceived illhealth in a sample of older, chronically ill American Indians. The elevated CESD scores associated with a variety of psychiatric diagnoses, including alcohol abuse or dependence, may be explained by several mechanisms (Schuckit & Monteiro 1988). Alcohol use disorders and depressive disorders may have some causal relation to one another through biological or behavioral mechanisms. On the other hand, persons who have recently abused alcohol often experience anxious and depressive symptoms which may persist for weeks, apparently as a physiologic effect of alcohol withdrawal. In addition, depressive symptomatology may accompany psychiatric and non-psychiatric conditions (including alcoholism) as a result of functional impairment and problems of living, which in turn may be caused by the condition itself and/or by the social sequelae of psychiatric labelling. Frank (1974) and Dohrenwend et al. (1979) have discussed the concept of "demoralization," which may lead to help-seeking behavior and also may produce symptoms of anxiety and depression. The CES-D may be an indicator of demoralization, in addition to being sensitive to specific depressive syndromes. The Schedule for Affective Disorders and Schizophrenia, Lifetime Version (SADS-L) (Endicott & Spitzer, 1978). The SADS-L is a semi-structured diagnostic interview, designed to rule diagnoses in or out according to Research Diagnostic Criteria (Spitzer, Endicott & Robins 1978). For the current study, additional probes were added to ensure coverage of DSMIII-R criteria. In psychiatric inpatient samples, for scale scores derived from the interview, testretest reliabilities of .67-.78, internal consistencies of .58-.97 and intraclass reliabilities of .94-.99 were reported, except for formal thought disorder (Endicott & Spitzer, 1978). In a tribally heterogeneous sample of 10 American Indians, Shore et al. (1987) report very good interrater reliabilities (kappa coefficients ranging from .62 to 1.00). In the absence of any true "gold standard" for diagnosis, the SADS-L was chosen because it allows the use of clinical judgement in the use of probes and rapport-building (unlike a structured interview), while providing a guide which ensures coverage and notation of all pertinent symptoms (unlike a clinical psychiatric interview). It was felt that in the hands of a clinician well-trained in its use and familiar with the cultural group being studied, the SADS-L was a reasonable choice for gathering clinical psychiatric data. The Global Assessment of Functioning Scale (GAF). The GAF (American Psychiatric Association, 1987) is a revision of the Global Assessment Scale (Endicott et al. 1976) and the Children's Global Assessment Scale (Shaffer et al. 1983). It is a global assessment of psychological, social and occupational
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functioning according to clinical judgement. Ratings are made on a scale of 0-100. The scale has nine anchor points which are each described in a short paragraph. The scale is included in the DSMIII-R (American Psychiatric Association 1987) as an operationalization of Axis V. The Global Assessment Scale, which is very similar, has shown intraclass correlation coefficients of .69 to .91 (Endicott et al. 1976).
Procedure
Some subjects were interviewed in their homes, others in a room in the community health clinic. All interviews were conducted by one of four psychiatrists, including J.D.K., P.L. and J.B. All four had extensive cross-cultural experience, including experience working with American Indians. They were trained in the use of the SADS-L by an experienced SADS-L interviewer. After each SADS-L interview, the subject was asked to complete two self-report questionnaires, including the CES-D. Diagnostic procedures are described in detail elsewhere (Somervell et al. submitted). Data Analysis
For data analyses, both hand calculations and Statistical Analysis System (SAS) computer software were used. We have avoided the use of statistical significance testing, because of concerns about the appropriateness of such methods given the sampling problems to be discussed. Thus, in describing patterns of CES-D total score in subgroups of our sample, we display mean scores together with approximate 95% confidence intervals. The latter are meant for descriptive purposes only. CES-D total scores were calculated by the method described by Radloff (1977), weighting all items equally. Each item is so scored that a higher score indicates more symptomatology; the total is then the sum of all item scores. Where a particular item was not answered, the median score for that item was used. Confirmatory factor analyses were performed using the PRELIS and LISREL programs. Three factor structures were tested: a one-factor model, a four-factor model (Golding and Aneshensel 1989), and a three-factor model in which the "depressed affect" and "somatic" factors are collapsed (based on the work of Beals et al. 1991; Keane et al. submitted; and others). Both a covariance and a polychoric matrix were calculated, and the factor models were run for both. The results presented are based on the covariance input matrix. All diagnostic categories used in data analyses were based on the DSMIII-R consensus diagnoses (Somervell et al. submitted), for current diagnosis only.
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PHILIP D. SOMERVELL ET AL. RESULTS
The Sample The sample interviewed with the SADS-L included 130 persons who were members of the dominant tribe. 121 of these (93%) filled out the CES-D. One subject had failed to answer nine of the twenty items of the CES-D and was therefore excluded; none of the other subjects had more than three missing values on CES-D items. The resulting sample consists of 120 persons (Table I). Eight persons (80%) of the ten who were not included in the CES-D sample had a psychiatric diagnosis, compared to 30% of the subjects who completed the CES-D. Their mean age was also greater (60.7 years in the non-responders, compared to 42.5 years for those who completed the CES-D). TABLE I Persons completing the CES-D: Descriptive Statistics
Sex
Age
Educa~on
Categories
N
Percent
Female Male 17-24 25-34 35---44 45-54 55-64 65-74 75-84 College graduate 1-3 years college High school graduate Partial high school 7-9 years Less than 7 years
64 56 14 31 22 24 16 10 3 7 32 40 25 14 1
53.3% 46.7% 11.7% 25.8% 18.3% 20.0% 13.3% 8.3% 2.5% 5.9% 26.9% 33.6% 21.0% 11.8% 0.8%
Performance of the CES-D CES-D scores ranged from 0 to 40 (the theoretically possible range is 0-60). 20.0% of the sample scored at or above the cutpoint of 16 (the cutpoint suggested by Radloff [1977], based on her sample, and commonly used in other studies as suggesting probable clinically significant depression). Cronbach's alpha for the CES-D total score was ~86. Confirmatory factor analyses suggested that the single-factor model clearly gave an inferior fit to the data. Both the fourfactor and the three-factor model gave good fit, with virtually no difference between them (Table II). Examination of the correlation coefficient between the
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CES-D IN AMERICAN INDIANS TABLE II Fits for covariance models, CES-D scores
NULL 1-FACTOR 3-FACTOR 4-FACTOR
X2
df
X2/df
GFI
BFI
995 396 272 272
190 170 167 164
5.23 2.33 1.63 1.66
0.757 0.817 0.819
0.68 0.85 0.84
Legend: GFI = Joreskog & Sorbom's goodness of fit index (Joreskog & Sorbom, 1989). NFI = Bentler & BoneR's Normed Fit Index (Bentler & Bonett, 1980).
TABLE III Correlations between CES-D factor scores Somatic/Affective Somatic/Affective Interpersonal 0.596 Positive --0.548
Interpersonal
-0.339
Positive
-
TABLE IV CESD: Three-factor model. Item loadings on each factor (with standard errors) Somatic/Affective Bothered Appetite Blues Mind Depressed Effort Failure Fearful Sleep Talk Lonely Cry Sad Getgoing
0.371 0.432 0.419 0.305 0.516 0.412 0.313 0.470 0.557 0.350 0.686 0.232 0.617 0.367
Positive Affect (0.076) (0.057) (0.055) (0.061) (0.059) (0.101) (0.066) (0.062) (0.076) (0.084) (0.069) (0.041) (0.064) (0.072)
Good Hopeful Happy Enjoy
0.305 0.484 0.758 0.663
Interpersonal (0.108) (0.095) (0.070) (0.064)
Unfriendly 0.411 (0.077) Dislike 0.605 (0.076)
depressed affect and somatic factors (.95 - Table III) suggested that the threefactor model was the most parsimonious. For this model, Chi-Square (167)=272, GFI=.817 (Table II). The items of the three factors, and their factor loadings, are shown in Table IV. "Crying spells" was the most problematic item; men, in particular, endorsed this symptom at only a very low level. Excluding it from the model would lead to a somewhat better fit. The three-factor model was chosen
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as the best, consistent with the conclusions o f several other investigators (Beals et al. 1991; Keane et al. submitted; Kuo 1984; Ying 1988; Guarnaccia et aL 1989). TABLE V CES-D total scores in demographic and clinical subgroups Group
N
Mean CES-D
56 64
10.2 9.0
12 15 17 75
17.6 12.8 I 1.7 7.2
53 44 23
8.1 10.0 12.3
7 4 11 84
23.6 11.8 9.1 7.4
+ 1.96 S.E.
Sex
Male Female GAF Score -71 Alcohol Never dependence/abuse Past dependence/abuse Current depend/abuse Current psychiatric diagnosis Any depression Any anxiety Alcohol dependence None
7.8, 12.6 7.0, 11.0 11.1, 6.9, 8.0, 5.8,
24.t 18.7 15.4 8.6
5.8, 10.4 7.7, 12.3 8.4, 16.2 14.5, 9.8, 5.2, 6.0,
32.8 13.8 13.0 8.8
Legend: "Any depression": Any depressive disorder, no alcohol dependence. "Any anxiety": Any anxiety disorder, no depressive disorder, no alcohol dependence. GAF: A score of 50 or less indicates "serious symptoms ... or any serious impairment in social, occupational, or school functioning (e.g., no friends, unable to keep a job)" (APA, 1987). A score of over 70 indicates no more than transient symptoms which are expectable reactions to psychosocial stressors; no more than slight impairment in functioning.
Associations o f CES-D Scores These relationships are presented descriptively in Table V. W e have not performed formal tests o f statistical significance, due to our concerns about the validity of such an analysis given the sampling methods used. However, Table V suggests that the differences if tested would not be statistically significant. CESD scores were slightly higher in men than in women, but showed no consistent trend with age. There was a tendency for persons with a current diagnosis of alcohol abuse or dependence to have higher scores than persons never having qualified for such a diagnosis. Persons with a past diagnosis had an intermediate mean score. Analyses using a different, exploratory, choice o f diagnostic categories showed a trend for subjects with depressive disorders to have higher C E S - D total scores than subjects in certain other diagnostic categories (who in turn had higher scores than those without any S A D S - L psychiatric diagnosis).
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511
However, the weakness of these trends, and the variability within each of the three groups, suggest that even if we had more confidence in the sampling methods, these patterns in the data would be suggestive at best. Mean scores also showed a weak trend to be inversely related to scores on the General Assessment of Functioning (GAF) scale; like the other patterns described, this would most likely not be statistically significant, judging from the amount of within-group variation. Examining the co-occurrence of SADS-L/DSMIII-R diagnoses, the odds ratio for the association of alcohol abuse or dependence and depressive disorders was 1.22. The 95% confidence limits (0.24, 6.32) on this odds ratio include 1.00, which is equivalent to a nonsignificant association. The same caveats as above apply to this analysis.
DISCUSSION Perhaps the first question to ask about any assessment tool is its acceptability. Ten of the 130 subjects who completed SADS-L interviews refused the CES-D. These ten subjects were older and more likely to have a psychiatric diagnosis than those who responded to the CES-D. The CES-D appears much less intrusive than the SADS-L interview as to its content, and is certainly much shorter. However, it is a self-report, paper-and-pencil questionnaire; perhaps this made it less acceptable (or less interesting) than the interview, which involved social interaction. However, it is also possible that by the end of the SADS-L interview, the respondents were simply tired or had reached the limits of their patience. In factor analyses, the high correlation between the depressed affect and the somatic distress factors suggested that they be collapsed into a single factor. The lack of a clear distinction between somatic and affective items is similar to what has been reported with some Asian-American and Latino samples. Western scientific culture tends to make a clear distinction between affective and psychological states, on the one hand, and bodily sensations on the other. This way of structuring experience and language is far from universal (Kleinman & Kleinman 1985). Rather, it has been pointed out that (for example) the "somatization" of depression is common and, in some populations, normative; a person may express severe depression in an idiom of physical distress, which in fact is how he/she perceives it (Katon et al. 1982). Our results support such an interpretation in this American Indian sample. However, it would be a mistake to overemphasize the differences between our sample and others in this respect. Even in white samples for which affective and somatic factors are more distinct, the internal consistency of the total CES-D score is approximately as high as in our sample and the four-factor scales are moderately intercorrelated.
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We report elsewhere (Somervell et aL submitted) that the use of factor scores (instead of total scores) did not enhance the specificity or sensitivity of the CESD. That suggests that while the factor scores represent more precisely defined clusters of symptoms than the total score, these clusters may not correspond well to the clinical construct of depressive disorders in this American Indian sample. In other words, the clustering of CES-D symptoms endorsed by these persons does not correspond well to the patterns of symptoms used by DSMIII-R to define depressive disorders. However, this interpretation must be tempered by the observation that subjects were not free to endorse any symptoms, but were constrained by the list of CES-D items. The CES-D provides only a limited selection of the DSMIII-R criterion symptoms of depressive disorders, and even the time-frame is different. Certain other patterns seen in the data are consistent with the notion that while CES-D scores discriminate persons with depressive disorders, they also reflect other psychiatric conditions and impairment in overall functioning. Persons with alcohol abuse or dependence diagnoses, as well as persons with other psychiatric diagnoses, tended to have lower scores than persons with depressive disorders, but somewhat higher scores than persons with no diagnosis. There was a consistent trend for lower GAF scores to be associated with higher CES-D scores. However, since the GAF is based partly on symptoms ascertained from other sources, this correspondence is to some extent to be expected. All of these patterns are at most suggestive, because they appear both weak and nonsignificant, and because of sampling issues to be discussed. One of our interests was in depressive symptomatology among persons with diagnoses of alcohol dependence or abuse. The comorbidity of affective disorders and alcohol use disorders is important because of its implications for treatment, and because of the difficulty of differential diagnosis of depressive symptoms in the presence of alcohol use disorders. It is worth nothing that the patterns seen in our sample, if considered descriptively and without regard for statistical significance, are broadly consistent with other reports on comorbidity: a positive (though very weak) relation between alcohol abuse/dependence and depressive disorders, as well as between alcohol abuse/dependence and depression symptom scores. However, for reasons having to do with the sampling design used in this study, we do not think that findings (whether positive or negative) on comorbidity are trustworthy in this study. This is why we have avoided tests of statistical significance. The sampling problem is nearly universal in studies of American Indian and Alaska Native populations, so we think it is worthy of detailed discussion. In general, when such studies have used general population samples at all, they have used samples of convenience. Typically, informants are asked to suggest other potential respondents, and networks of acquaintances are tapped. This runs counter to the mainstream of epidemiologic research, in which probability
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513
sampling is practically a sine qua non for any community-based observational study. A probability sample is one in which each person in the sampling frame (generally the population at large) has a known probability of being selected into the sample. It can be difficult to design a probability sampling scheme, and it can be a major undertaking to execute it. However, probably the major reason which has been cited for convenience sampling in studying Native communities is the concern that soliciting the participation of persons with whom the investigator is not acquainted may so offend them and the community as to jeopardize the researcher's access to that community. Since one cannot always count on wholehearted support from the entire community, and research is a sensitive issue among Native people, the risks are real. However, we will argue that in view of the limitations which the use of convenience samples imposes on the results, there is a need for a concerted effort to overcome these obstacles. It is a commonplace among epidemiologists and statisticians that sampling (or selection) patterns can invalidate the results of a study. There are two general issues here. First, all statistical methods are based on the assumption of probability sampling. Secondly, even in qualitative terms, if certain kinds of people are more likely than others to be in the sample, what is seen in that sample may be very misleading as an indication of what would be seen in the population at large. One example of this type of effect is of particular interest to those who study comorbidity. It appears to have first been discussed by Berkson (1946); the phenomenon has become known as Berkson's bias. The context was a type of study in which hospitalized patients were investigated to test the role of one disease as a cause of some other disease. Berkson showed that spurious results could be produced - e.g., an apparent association between the two diseases which did not reflect any such pattern in the general population - because of different prevalence rates for the two diseases in the general population, and different hospitalization rates for persons with the respective diseases. It is noteworthy that the concept of Berkson's bias deals only with the m a t h e m a t i c a l effect of overlapping prevalences and selection probabilities of individual disorders. It does not deal with the qualitative issue of the effects of symptomatology and impairment on people's behavior. Yet we should not find it surprising if, for subjective or behavioral reasons, people with more than one disorder have higher hospitalization rates than would be predicted based on the hospitalization rates for either disorder alone. Such an effect might then be a d d e d to that produced by Berkson's bias per se. The conditions under which Berkson's bias can occur have been further discussed by Boyd (1979) and by Roberts et al. (1978). Theoretically, it can either inflate or minimize the apparent associations between medical conditions, and in at least one large dataset it has been shown that this can indeed occur (Roberts et al. 1978). How does this pertain to the data which we have presented? In both a community-based study using a convenience sample and a hospital-based study,
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a person's likelihood of entering the sample is not random, and the factors influencing this likelihood are not only out of the investigator's control, but not fully ascertainable. In fact, where psychological issues are the subject of study, a person's likelihood of entering the study sample (selection rate) is likely to be correlated with some of the factors to be studied - just as hospitalization rates are related to which disease(s) a person suffers from. Psychiatric disorder and symptomatology may be reflected in personality style and social behavior (e.g., withdrawal versus gregariousness), extensiveness of social networks, and perceived approachability. These characteristics, in turn, may affect a person's probability of being in the sample. Since the prevalences of disorders and symptoms also differ, the conditions for Berkson's bias seem to be met. The conditions for other forms of bias based on behavior patterns (as mentioned earlier) exist as well. This pertains to any analyses of associations between different study factors. The objection may be raised that drawing a probability sample is of little use if (as often happens) a substantial proportion of subjects refuse to participate: refusal is not a random event, being correlated with demographic, health-related and behavioral factors. In fact, this is seen in our sample, where those subjects who refused the CES-D were older and more likely to have a diagnosis than those who consented. However, it is possible to assess the potential effects of refusals on the study results, and one can attempt to do something about it. One can estimate, using a range of assumptions about sampling rates and prevalences, how the results might hypothetically have been distorted. In the most favorable case, this might lead to the conclusion that the bias cannot have been severe. One can also devote ingenuity and effort to recruiting a random sample of the refusers (even if only to collect more limited data from them). One can use these special data from refusers to estimate how the research results might be different if they had participated in the study itself. With a convenience sample, none of this is possible. There is another alternative: to study the entire population of interest (e.g., all adults in the community). In most epidemiologic studies, the reason not to do so is that the numbers are too large - a reason which is not always compelling in a village (for example) of a few hundred persons. Here, the issue to be confronted is, rather, community acceptance of the research enterprise. In fact, Sampath (1974) used just such an approach in his study of an Eskimo village on Baffin Island (Canada). In non-Native populations, an example is provided by the Evans County Study (McDonough et al., 1963; Hames, 1971), conducted in a rural county in the state of Georgia. This approach will not always be practical. However, where it can be used, it will solve the scientific problem, and it may have the beneficial side-effect of forcing the research enterprise to be truly responsive to the concerns of the community.
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NOTE 1 The preparation of this manuscript was supported by NIMH Grant No. R03 MH45167--01A1 and NIMH Grant No. 5R01 MH42473. Drs. Somervell, Beals and Manson are located at the National Center for American Indian and Alaska Native Mental Health Research in the Department of Psychiatry, University of Colorado Health Sciences Center. Drs. Kinzie, Boehnlein and Leung are at the Department of Psychiatry, the Oregon Health Sciences University. Correspondence concerning this article should be sent to Philip D. Somervell, Ph.D., Department of Psychiatry, Campus Box C249-17, University of Colorado Health Sciences Center, Denver, Co 80262.
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National Center for American Indian and Alaska Native Mental Health Research Department of Psychiatry University of Colorado Health Sciences University Denver, Colorado 80262
