A reexamination of the factor structure of the Center for Epidemiologic Studies Depression Scale: is a one-factor model plausible?

The Center for Epidemiologic Studies Depression Scale (CES–D; Radloff, 1977) is 20-item self-report questionnaire that is one of the most widely used measures of depressive symptoms in research today. According to Radloff (1977), the scale was constructed to measure the symptoms of depression in the general population on the basis of factors identified in both the clinical literature and factor analytic studies. The scale was designed to represent multiple dimensions of depression as well as discourage response bias (through the use of reverse-scored items) and assess positive affect. Assessments using the CES–D typically focus on the preceding week, which is the time frame suggested in the original scale. However, researchers often use alternative time frames to accommodate their research questions, which may alter the psychometric properties of the scale. In 1977, Radloff introduced the scale with support for adequate criterion-oriented validity, construct validity, internal consistency, and test–retest reliability. The underlying structure was examined using principle components analysis (PCA) with varimax rotation (Radloff, 1977). Four components were estimated, accounting for 48% of the variance, and items with component loadings of at least .40 were included. The four components and the corresponding items were reported as follows: (a) depressed affect, including feeling blue, feeling depressed, feeling lonely, crying spells, and feeling sad; (b) positive affect, including feeling as good as others, feeling hopeful, feeling happy, and enjoying life; (c) somatic and retarded activity, including being bothered more than usual, decreased appetite, feeling as if extra effort was required, reports of restless sleep, and difficulty getting going; and (d) interpersonal, including feeling that others were unfriendly and feeling disliked by others. The final four-component solution did not include difficulty concentrating, talking less than usual, feeling like a failure, or feeling fearful items. Since 1977, the CES–D has become a very popular measure of depressive symptoms and is used frequently in both epidemiological and clinical research. There have been several attempts to determine the most appropriate factor structure, both in the general population and in unique populations. Support for the four-component structure has been replicated using PCA with several samples, including urban residents (Clark, Aneshensel, Frerichs, & Morgan, 1981), married men and women (Ross & Mirowsky, 1984), primary care patients (Devins, Orme, Costello, & Binik, 1988; Zich, Attkisson, & Greenfield, 1990), university students (Devins et al., 1988), and both English- and Spanish-speaking psychiatric inpatients (Roberts, Vernon, & Rhoades, 1989). Researchers using PCA have also found support for a three-component structure, specifically in ethnically diverse samples (e.g., Guarnaccia, Angel, & Worobey, 1989; Kuo, 1984; Manson, Ackerson, Dick, Baron, & Fleming, 1990; Stroup-Benham, Lawrence, & Trevino, 1992; Ying, 1988). The three-component structures combined the somatic and depressed affect domains (Guarnaccia et al., 1989; Kuo, 1984; Stroup-Benham et al., 1992; Ying, 1988) or the depressed affect and interpersonal domain (Manson et al., 1990). Finally, a five-component structure has been proposed (Thorson & Powell, 1993); however, this structure has not been widely supported elsewhere. Using exploratory factor analysis, several studies replicated Radloff’s four-component structure, including one using samples of undergraduates (Joseph & Lewis, 1995) and one using samples of chronically ill older adults (Callahan & Wolinsky, 1994). However, Stommel et al. (1993), using samples of cancer patients and caregivers, were not able to replicate the four-component structure using exploratory factor analysis. Using confirmatory factor analysis (CFA), Radloff’s four-factor structure of the CES–D has been supported in several populations, including White, Black, and Hispanic adults (Roberts, 1980) and Mexican Americans (Garcia & Marks, 1989; Golding & Aneshensel, 1989; Posner, Stewart, Marin, & Perez-Stable, 2001). However, several research groups using CFA reported a three-factor structure for samples of American Indian participants, including adolescents (Dick, Beals, Keane, & Manson, 1994), adults (Somervell et al., 1992), and elders (Chapleski, Lamphere, Kaczynski, Lichtenberg, & Dwyer, 1997). In addition to the four-factor and three-factor solutions, several research groups using CFA reported a four-factor structure with a single second-order factor; this structure was supported in samples of community adults (Hertzog, Van Alstine, Usala, Hultsch, & Dixon, 1990), adult women (Knight, Williams, McGee, & Olaman, 1997), and rheumatoid arthritis patients (Sheehan, Fifield, Reisine, & Tennen, 1995). Sheehan et al. (1995) found that the single, three-, four-, and single second-order factor models all provided good model fit to the data as assessed by fit measures such as the chi-square statistic and the ratio of chi-square over degrees of freedom (Wheaton, Muthen, Alwin, & Summers, 1977). The models were then compared using several additional indices, including chi-square, Akaike’s information criterion (AIC; Akaike, 1974), consistent Akaike’s information criterion (CAIC; Bozdogan, 1987), root mean square error of approximation (RMSEA; Steiger, 1990), and the comparative fit index (CFI; Bentler, 1990). After using these various measures to contrast fit, the authors ultimately endorsed the original four-factor model, χ2(164) = 247, χ2/df = 1.51, RMSEA = .026, AIC = 339, CAIC = 597, CFI = .988 (Sheehan et al., 1995). The authors reported that this fit was almost identical to that of the four-factor model with a single second-order factor and had no significant differences in fit, which is not surprising as these models are nearly equivalent. However, the authors indicated that the four-factor model may provide slightly more information and is in line with the scale’s theoretical development. Although the literature supports a four-factor structure for the CES–D, this is not the model generally used in research. Even though Radloff (1977) reported the best fit for four components and a high degree of structural similarity across samples, she argued that a total score should be used because all of the scale items were conceptually related to depression and thus should be included regardless of the component loadings. In line with this recommendation, it is common practice to report a total scale score in both clinical assessment and research. In a review of the literature across several notable journals (i.e., Behaviour Research and Therapy, Health Psychology, Journal of Applied Psychology, Journal of Consulting and Clinical Psychology, Journal of Clinical Psychology, Journal of Personality Disorders, Journal of Personality and Social Psychology, Psychological Assessment), all studies using the CES–D as a primary measure were identified and examined. Conducting a search using PsycINFO as well as Google Scholar, we were able to locate 114 studies published since 2000 that used the 20-item CES–D. Of these articles, only seven mentioned the factor structure of the measure; two of these studies were examining factor structure explicitly. The remaining 107 studies reported use of a total score that combined all items of the measure. Although reporting the CES–D with a total score has become common practice, none of the known research conducted to date has demonstrated that the CES–D is unidimensional. Using a unidimensional score for data that cannot be adequately explained with a single factor can lead to several types of interpretation errors, resulting in faulty conclusions. For example, if the CES–D is, in fact, best conceptualized as a multidimensional model with four factors, analyses using a total score could lead to conclusions that misrepresent subtypes of depressive presentations or underappreciate the role of specific symptom clusters. Alternatively, if the CES–D can be adequately interpreted as measuring a single construct, individuals with different depressive symptom presentations can be equated in terms of depressive symptom severity. Thus, our primary aim is to examine the factor structure of the CES–D to determine if a one-factor solution is an adequate fit of the data as compared with the four-factor model suggested by Radloff (1977) as well as alternative models.