Associations Among Social Support, Income, and Symptoms of Depression in an Educated Sample: The UNC Alumni Heart Study

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1 INTERNATIONAL JOURNAL OF BEHAVIORAL MEDICINE, 10(3), Copyright 2003, Lawrence Erlbaum Associates, Inc. Associations Among Social Support, Income, and Symptoms of Depression in an Educated Sample: The UNC Alumni Heart Study Beverly H. Brummett, John C. Barefoot, Peter P. Vitaliano, and Ilene C. Siegler It has been suggested that the inverse association between social support and depression may be stronger in persons with lower income. This study tested the support income hypothesis in a sample of 2,472 individuals enrolled in the UNC Alumni Heart Study. The income was examined as a moderator of the relation between support and self-reported ratings of symptoms of depression. The appraisal subscale of the Interpersonal Support Evaluation Scale, household income level, and their interaction were modeled as predictors of depression ratings. The support income interaction term was significantly associated with symptoms of depression, F(2, 2471) = 4.71, p =.007. Social support was more strongly associated inversely with depression ratings in persons with lower income as compared to those with higher income. The present results extend previous work regarding the moderating effect of income to a sample of relatively high education and income level. Key words: income, social support, depression, distress Beverly H. Brummett, John C. Barefoot, and Ilene C. Siegler, Duke University Medical Center, Durham, NC, USA; Peter P. Vitaliano, Department of Psychiatry and Behavioral Sciences, University of Washington, Seattle, WA, USA. This research was supported by Grants R01-AG12458 from the National Institute on Aging, R01- HL55356 and P01-HL36587 from the National Heart Lung and Blood Institute, and R01-MH57663 from the National Institute of Health. Correspondence concerning this article should be addressed to Beverly H. Brummett, Duke University Medical Center, Box 2969, Durham, NC 27710, USA. brummett@acpub.duke.edu

2 240 BRUMMETT, BAREFOOT, VITALIANO, SIEGLER It is generally accepted that perceptions of social support are associated with psychosocial and health outcomes (Berkman, 1995; Horsten, Mittleman, Wamala, Schenck-Gustafsson, & Orth-Gomer, 2000; Kaplan & Toshima, 1990; Ruberman, Weinblatt, & Goldberg, 1984; Williams et al., 1992). Likewise, research has shown that level of income is related to general well-being and mortality (Backlund, Sorlie, & Johnson, 1999; Diener, Suh, Lucas, & Smith, 1999; Kaufman, Long, Liao, Cooper, & McGee, 1998). Much of the past research, however, has been built on main effects models, and more complex interactional perspectives are needed to take the next step in our understanding (Taylor & Seeman, 1999). It has been hypothesized that the association between social support and distress may be stronger in persons with lower income in part because of their potential lack of resources. The resources hypothesis is based on the proposition that psychological distress in the presence of environmental stressors is a negative function of a person s coping resources and a positive function of their vulnerability (Vitaliano, Dougherty, & Siegler, 1994; Vitaliano, Russo, Young, Teri, & Maiuro, 1991). Support for this hypothesis has been found in diverse samples. Social support was a stronger predictor of recovery from depression among cardiac patients who had lower income compared to those with higher income (Barefoot et al., 2000). Similarly, in a sample of spouse caregivers of persons with Alzheimer s disease and matched controls social support was more beneficial in persons with lower income with respect to physiological responses (Vitaliano et al., 1999, 2001). In addition, variation in blood pressure among individuals of different social classes has been associated with perceptions of social support (Dressler, Grell, Gallagher, & Viteri, 1992). Finally, research conducted by Strogatz and James (1986) has shown that the relation between hypertension and emotional support among Blacks is specific to persons with low income. This study used data from the University of North Carolina Alumni Heart Study (UNCAHS) to further examine the hypothesis that the association between social support and distress is dependent on household income level. With respect to the present sample the lack of resources hypothesis predicts that distress (i.e., ratings of depressive symptoms) will be a multiplicative function of social support and income level. Unlike the above-noted studies that have examined this hypothesis, the UNCAHS sample consists primarily of college-educated individuals living in households reporting moderate to higher income, thereby affording an opportunity to explore the boundaries of the lack of resources theory. Demonstration of the hypothesized finding in the present sample would suggest that the association between support and distress may not be unique to persons at the lower ends of the income distribution. In addition to income level, two other financial measures (i.e., sufficiency of income and financial pressure ratings) were used to explore the lack of resources hypothesis. Specifically, if insufficient financial resources underlie the need for support in the lower income groups, the measures of perceived financial adequacy

3 INCOME, SUPPORT, AND DEPRESSION 241 (i.e., sufficiency and financial pressure) should follow a pattern similar to that of income, for example, individuals reporting financial concerns should benefit more from social support as compared to those reporting fewer financial worries. Finally, studies have shown that other measures of socioeconomic status (SES) may have differential relations to health behavior, mortality, and distress (Liberatos, Link, & Kelsey, 1988). Therefore, the potential effects of two additional measures of SES (i.e., education level and occupational prestige) were also explored in this study. Thus, this study provides an opportunity to significantly extend previous findings. METHODS Participants The UNCAHS is an ongoing prospective study of coronary heart disease and coronary heart disease risk that started its prospective data collection in when alumni were in their early 40s (Siegler et al., 1992a; Siegler, Peterson, Barefoot, & Williams, 1992b). This study sample consisted of 2,472 UNCAHS participants who had data available for the primary measures of interest (i.e., ratings of depression, social support, and income). This sample reflects the sociodemographic characteristics of the UNC student population in the 1960s, with minority enrollment less than 1%. Measures Psychosocial and demographic measures examined in this study were drawn from UNCAHS follow-up data. Table 1 shows the timeline for the collection of all measures analyzed in this article. Table 2 provides the sample characteristics TABLE 1 Time Table for Collection of Study Measures Study Measure Time (Wave) of Data Collection Social support Study Wave 3 ( ) Income Study Wave 3 ( ) Sufficiency of income Study Wave 3 ( ) Education level Study Wave 3 ( ) Occupational prestige Study Wave 3 ( ) Financial concerns Study Wave 2 ( ) Symptoms of depression Study Wave 6 ( ) Note. The dropout rate for individuals who had the required data at Wave 3 but did not provide data at Wave 6 was 1%.

4 242 BRUMMETT, BAREFOOT, VITALIANO, SIEGLER TABLE 2 Sample Characteristics Characteristic Value Gender 77.8% male Age, mean (SD) 42.8 (1.3) Marital status 80.2% married Education level Some college, no degree 6.9% College degree 18.3% College degree + training 27.2% Masters degree 24.1% Doctorate/Law/Medical 23.5% Symptoms of depression CES-D, mean (SD) 8.2 (7.7) Scored 16 or above on CES-D 14.1% Appraisal of support, mean (SD) 32.3 (6.1) Income Low: below $50, % Moderate: $50,000 99, % High: $100,000 and above 27.7% Sufficiency of income, median 7 Financial pressure, median 3 Occupational prestige, mean (SD) 61.0 (18.1) Note. Range for sufficiency of income and financial pressure is 1 10, higher scores represent greater sufficiency and pressure. including the means and standard deviations, or frequencies where appropriate, of the study variables described later. Finally, Table 3 presents the relations among the independent measures. Social support. In the UNCAHS social support was assessed using the 10-item appraisal subscale of the Interpersonal Support Evaluation Scale (ISEL) (Cohen, Mermelstein, Kamarck, & Hoberman, 1985). The ISEL was designed to assess perceptions of the availability of social resources. The appraisal subscale primarily captures perceptions regarding the availability of someone to discuss his or her problems with, for example, There are several people who I trust to help solve my problems. The ISEL appraisal subscale has demonstrated adequate internal reliability (α coefficient =.77.92) in general population samples (Cohen et al., 1985). Appraisal scores range between 10 and 40. Higher scores on the ISEL indicate positive perceptions of social support. Household income. Income was assessed using an 11-level categorical item that asked participants to categorize their annual household income between the following extremes: 1 = below $10,000 to 11 = $300,000 and above. Two

5 INCOME, SUPPORT, AND DEPRESSION 243 TABLE 3 Pattern of Correlations Among Independent Measures Variable Social support 2 Income.04* 3 Occupational prestige.02.15* 4 Education level.03.21*.53* 5 Sufficiency of income.12*.48*.07*.10* 6 Financial pressure.06*.16*.10*.07*.41* Note. For sufficiency of income and financial pressure, higher scores represent greater sufficiency and pressure. *p <.05. statistics reported by the U.S. Census are helpful to put the present income ratings (Table 2) in context. During 1990 the median annual income reported for all households was $29,943 and the median annual income for men years of age with Bachelor s degree was $62,174 (U.S. Census Bureau: census.gov/hhes/www/income.html). Thus, although the household income reported in this sample is likely to be high as compared to values reported by a random population sample, it is consistent with what would be expected given the characteristics of this sample (i.e., primarily college-educated men). Symptoms of depression. The Center for Epidemiologic Studies Depression Scale (CES-D) (Radloff, 1977) is a 20-item self-report scale designed to measure depressive symptomatology in a general population. The items were scored on a 4-point scale, with the total score ranging between 0 and 60. Higher scores on the CES-D represent depressive responses and a score of 16 or above is generally considered suggestive of a depressive disorder. Test retest correlations for the CES-D range between.45 and.70 (Radloff, 1977). Sufficiency of income. Along with reports of income, UNCAHS participants also responded to a measure indicating their perceptions of the sufficiency of their income that read as follows: How sufficient is your income when considering your commitments, responsibilities and the lifestyle choices you have made? Responses were rated from 1 (not at all sufficient) to 10 (more than sufficient). Financial pressure. The study participants also reported their perceptions regarding the amount of pressure in their lives due to financial issues by rating the following item (from 1 [no pressure] to 10 [extreme pressure]): pressure caused by financial issues.

6 244 BRUMMETT, BAREFOOT, VITALIANO, SIEGLER Education. In this sample education was treated as a 5-level categorical variable in analyses (see Table 2 for distribution). Occupational prestige. Occupational prestige was derived from a censusbased classification scheme that provides a score indicating the level of occupational SES (Stevens & Cho, 1985; Stevens & Featherman, 1981). Specific occupations across a broad range of categories receive a score that falls between 14 and 91, with higher scores indicating greater occupational prestige. UNCAHS coders classified occupational prestige scores from occupations reported at Study Wave 3. Analyses To examine the primary hypothesis a general linear model was estimated with household income level, social support, gender, and the two- and three-way interaction terms as predictors of CES-D ratings. Nonsignificant interaction terms were removed from final models. It was predicted that associations between support and symptoms of depression would be stronger among individuals reporting lower income. Statistical significance was set at p <.05 (two-tailed test) for this study. An identical analytic approach was applied to the additional measures of financial pressure, income sufficiency, education level, and occupational prestige. RESULTS The main effects and significant interaction results are provided in Table 4. With respect to the main effects, social support, financial concerns, and sufficiency of income ratings were significantly related to symptoms of depression. In contrast, level of education and occupational prestige ratings were unrelated to ratings of depression. The support income interaction term was a significant predictor of CES-D ratings such that support was more strongly associated with symptoms of depression for participants of lower household income compared to those who reported higher income levels. Figure 1 portrays the pattern of the support income interaction. Other two- and three-way interactions (gender income, gender support, gender income support) were nonsignificant (ps.78.98). The support financial adequacy interactions examined were statistically significant and followed a pattern similar to that of income. Figure 2 portrays the pattern of results for these findings. Analyses also revealed that neither the social support education interaction term nor the social support occupational prestige reached the level of statistical significance as a predictor of CES-D ratings ( p =.91; p =.584, respectively).

7 TABLE 4 Results of Main Effects and Interactions of Theoretical Interest Associated With Symptoms of Depression Main Effects Results Social support F(1, 2471) = 101.6, p <.001 Income F(2, 2471) = 16.5, p <.001 Financial pressure F(1, 2381) = 83.1, p <.001 Sufficiency of income F(1, 2463) = 70.1, p <.001 Education F(1, 2471) = 1.7, p <.200 Occupational prestige F(1, 2244) = 0.61, p <.436 Interactions Social support income F(2, 2471) = 4.86, p =.007 Social support financial pressure F(1, 2381) = 14.32, p =.001 Social support income sufficiency F(1, 2463) = 13.58, p =.001 Social support education level F(1, 2461) = 0.75, p =.387 Social support occupational prestige F(1, 2244) = 0.42, p =.517 Note. All models adjusted for gender. FIGURE 1. Social support (SS) household income interaction as a moderator of symptoms of depression (CES-D ratings). 245

8 FIGURE 2. Social support (SS) income adequacy interactions as moderators of symptoms of depression (CES-D ratings). 246

9 INCOME, SUPPORT, AND DEPRESSION 247 DISCUSSION The present results extend previous findings by demonstrating a social support income interaction in middle-aged persons of relatively high income and education level. Indeed, examination of these findings showed that social support seemed inconsequential with respect to CES-D scores only in the very high income group. For some this may call into question the feasibility of a lack of resources hypothesis. However, in this baby boom sample it is possible that relatively high levels of income are necessary to perceive that there is no need for a social buffer with respect to monetary concerns. Finally, in addition to providing support for the support income interaction hypothesis, the present findings suggest that social support, income, income sufficiency, and concerns regarding financial pressure have a substantial main effect with respect to symptoms of depression. Unlike prior research in this area, this article provides support for the support income interaction by analyzing income from three different perspectives. Specifically, when our measure of absolute household income was replaced with measures that are somewhat more subjective and may more closely capture the relative nature of income, persons with lower ratings of income sufficiency and higher ratings of financial pressure benefited more from social support as compared to those with lower ratings. Such findings may provide indirect support for Wilkinson s theory that perceptions of an individual s place in the social hierarchy, and the resulting health effects of such perceptions, are based on the relative position of the income level rather than the absolute level (Wilkinson, 1996). Indeed, results of post hoc analyses that included the interactions of all three indicators with social support simultaneously showed that the measure of financial pressure was the strongest predictor of symptoms of depression. As previously mentioned, different measures of SES may have differential relations with health outcomes (Davey-smith et al., 1998; Liberatos et al., 1988). Such findings may be expected given the differential attributes of SES measures. For example, occupational prestige and income are likely to fluctuate during a lifetime, whereas education level is likely to remain stable following the decade of the 20s (Davey-smith et al., 1998; Liberatos et al., 1988). With respect to both main effects and interaction models, education level and occupational prestige did not demonstrate a pattern of results similar to that of the income in this study. This lack of association has also been demonstrated by Vitaliano (Vitaliano et al., 2001) who found that, across time, social support was more beneficial in persons with lower income, but not with lower education, with respect to physiological responses. Thus high levels of income may offer a feeling of security with respect to fewer needs for social support that is not provided by other SES indicators. However, it is also possible that the lack of a significant relationship for the measures of education and occupational prestige in this study were due to the restricted range of these measures in this relatively high SES sample.

10 248 BRUMMETT, BAREFOOT, VITALIANO, SIEGLER A well-known alternative hypothesis exists that may also account for the present pattern of findings. Cohen and Wills (1985) proposed a stress-buffering hypothesis with respect to the positive association between support and well-being. The buffering hypothesis suggests that support is protective during times of stress. Thus, in this study low income might be viewed as a stressor that is moderated by social support. Indeed, related research in older adults has shown that informational support buffers the effects of chronic financial strain with respect to depressive symptoms (Krause, 1987). In this article it is empirically impossible to determine which interpretation is most correct. There are several points that should be considered with regard to interpreting these findings. It should be noted that these findings may not be generalized to sample of lower income and education levels. In addition, few of our participants reported high ratings on the CES-D, nor did they report extremely low levels of social support. However, the pattern of results was fairly consistent across several outcome measures. Also, group differences larger than 3 points on a measure with a standard deviation of 7.7 are typically considered sizable. In addition, this study included only the appraisal subscale of the ISEL, therefore these findings may not be generalized to other areas of support (i.e., self-esteem, belonging, and tangible support). Furthermore, it has been suggested that symptoms of depression influence how a person rates his or her social support, as opposed to social support influencing ratings of depression. It is not possible to refute this entirely, however, results of prospective studies suggest that this is probably not the case (Blazer & Hughes, 1991; Krause, Liang, & Yatomi, 1989; Lin & Dean, 1984). Adler, Boyce, Chesney, Folkman, and Syme (1993) noted that the relation between SES and health outcomes is not limited to those of low income. It is not clear, however, whether the mechanisms that underlie the SES and health association are the same at the lower and the upper ends of the SES spectrum. Prior research examining the present association between social support and distress at different levels of income has demonstrated this finding in primarily lower income individuals and individuals who are experiencing significant life stress (i.e., patient and caregiver samples). Thus, these findings contribute to the literature in this area by suggesting that the relation between psychological distress and social support occurs at moderately high levels of SES and therefore may moderate the association of SES and health even at the upper ends of the SES gradient. REFERENCES Adler, N. E., Boyce, T., Chesney, M. A., Folkman, S., & Syme, S. L. (1993). Socioeconomic inequalities in health. Journal of the American Medical Association, 269(24),

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