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J Sleep Res. Author manuscript; available in PMC 2017 February 01. Published in final edited form as: J Sleep Res. 2016 February ; 25(1): 70–77. doi:10.1111/jsr.12333.
Perceived Discrimination and Youths’ Adjustment: Sleep as a Moderator Mona El-Sheikha, Kelly M. Tua, Ekjyot K. Sainia, Thomas E. Fuller-Rowella, and Joseph A. Buckhaltb
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aDepartment
of Human Development and Family Studies, Auburn University, AL
bDepartment
of Special Education, Rehabilitation and Counseling, Auburn University, AL
Summary
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Adolescents’ sleep duration was examined as a moderator of the association between perceived discrimination and internalizing (anxiety, depression) and externalizing symptoms. Participants were 252 adolescents (M = 15.79 years; 66% European American, 34% African American) who reported on their perceived discrimination (racial and general) and adjustment. Sleep duration was measured using actigraphy. Moderation effects were evident. The lowest levels of internalizing symptoms were observed for adolescents with longer sleep duration in conjunction with lower levels of perceived racial discrimination. Further, general perceived discrimination was more strongly associated with externalizing behaviors for youth with shorter versus longer sleep. Findings highlight the importance of sleep as a bioregulatory system that can ameliorate or exacerbate the effects of discrimination on youths’ adjustment.
Keywords racial discrimination; general discrimination; actigraphy; internalizing; externalizing
Introduction
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Perceived discrimination is a risk factor for psychological problems in children and adults (for reviews see Williams & Mohammed, 2013 and Schmitt et al., 2014). In particular, studies have found associations with externalizing symptoms (Coker et al., 2009; FullerRowell et al., 2011), as well as with depression and anxiety (Greene et al., 2006; Yip, 2014). However, these effects are not uniform (Greene et al., 2006; Schmitt et al., 2014), and vulnerability and protective factors have been identified. Sleep is an important bioregulatory system that underlies emotional and behavioral regulation (Baum et al., 2014; Dahl, 1996). Yet, few studies have examined sleep as a moderator that may ameliorate or amplify the effects of perceived discrimination on youths’ adjustment. The current study addresses this gap in the literature.
Correspondence: Mona El-Sheikh, Ph.D., Human Development and Family Studies, 203 Spidle Hall, Auburn University, Auburn, AL 36849-5214; Tel: 1-334-844-3294, Fax: 1-334-844-4515, [email protected]. Conflicts of interest: There are no conflicts of interest. Author contributorship: All authors contributed in a meaningful way to this manuscript.
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Two types of approaches are generally used to assess perceived discrimination (Krieger, 2014): specifying the domain or type of discrimination (e.g., racial/ethnic) (Fisher et al., 2000) or general reports of unfair treatment across a broader range of possible events (Krieger et al., 2005; Williams et al., 1997). For general unfair treatment, follow-up questions are sometimes used to specify one or more possible attributions. Both approaches have been commonly used and have demonstrated predictive validity in both African American (AA) and European American (EA) samples (e.g., Fuller-Rowell et al., 2012; Sellers et al., 2003). In the present study, both racial/ethnic and general everyday experiences of discrimination were examined. Racial/ethnic discrimination is defined as “perceptions of unfair treatment on the basis of one’s race/ethnicity”. General everyday discrimination refers to “perceptions of unfair treatment” and does not require an attribution to a specific personal characteristic.
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Some evidence, albeit scarce, has linked perceived discrimination with poor subjective sleep quality in youth (Huynh & Gillen-O’Neel, 2013). Sleep insufficiency is associated with increased negative emotions and emotion regulation difficulties (Baum, 2014), as well as internalizing and externalizing problems in youth (Kelly & El-Sheikh, 2014). Sleep problems may contribute to adjustment problems through their effects on brain processes critical for emotion and behavioral regulation (Dahl, 1996).
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To our knowledge, only one study has examined the moderating influence of sleep in the context of discrimination (Yip, 2014). In an adolescent sample, self-reported sleep quality, but not sleep period (bedtime to wake time), moderated the effects of racial/ethnic discrimination on depressive symptoms. High levels of perceived racial/ethnic discrimination accompanied by poor sleep quality was prospectively associated with depressive symptoms. Further, adolescents with the lowest depression were those with low discrimination in conjunction with better sleep. Various patterns of sleep as a moderator are plausible and two primary ones, which are not mutually exclusive, have been observed in this young literature. Several studies have yielded a moderation pattern of effects that is consistent with cumulative or dual risk risk perspectives (Evans, 2003; Sameroff, 1983), which propose that individuals may have a vulnerability that increases risk, or a protective factor that reduces risk, in the context of of an environmental stressor. For instance, short or poor quality sleep increased vulnerability for adjustment problems, whereas better sleep quality functioned as a protective factor, in the context of family and peer stress (Lemola et al., 2012; Tu et al., 2015).
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Findings from other studies have revealed a dual-protection or protective-reactive pattern of effects (Luthar et al., 2000), in which a protective attribute (better sleep) is benefical in low but not high risk contexts. Supportive of this pattern, children and adolescents with the highest level of adaptation were those with longer and better quality sleep in conjuction with low familial (Bernier et al., 2014; Bordeleau et al., 2012; El-Sheikh et al., 2014), peer (Tu et al., 2015), or socio-cultural risks (Yip, 2014). The present investigation examined actigraphy-based sleep minutes in relation to two domains of perceived discrimination (racial/ethnic and general unfair treatment) in the
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prediction of internalizing and externalizing behaviors in a sample of adolescents from predominantly rural and semi-rural Alabama. With evidence of dual-risk and dual-protection effects emerging in the literature on sleep as a moderator, it is possible that shorter sleep may increase risk and longer sleep may ameliorate risk in the association between discrimination and adjustment problems. It is also plausible that longer sleep may be protective against maladjustment in the context of low discrimination, but not high discrimination. Nevertheless, it is also possible that other moderation effects could emerge and our main objective was the identification of sleep as a moderator of risk and explicating the pattern of such effects.
Method Participants
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Data for the current study comes from the fourth wave (collected from 2012–2013) of the Family Stress Study conducted at Auburn University; neither the discrimination measures nor actigraphy data were collected at the earlier waves. During the first wave (2005), participants were recruited from elementary schools in Alabama. Children were from two parent homes and did not have a diagnosis of attention deficit hyperactivity disorder, developmental delays, or a chronic illness. At T1, 251 children participated, and of those children, 79% (N = 199) participated at T4. To increase sample size, an additional 53 youth were recruited for the present wave using the same inclusion criteria, and from the same schools as the original sample. No differences across study variables emerged between participants recruited at T1 versus T4.
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The full analytic sample was composed of 252 adolescents (118 boys, 134 girls, 66% European American (AA), 34% African American (AA) between the ages of 14 and 18 (M age = 15.79 years, SD = .81). The ethnic/racial composition of the sample is representative of the area. Family income-to-needs ratio (annual family income divided by the poverty threshold considering the family size; U.S. Department of Commerce, 2013) indicated that ~ 42% of families were living below or near the poverty line (ratio < 2) and 36% were middle class (ratio ≥ 3). Procedure
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The study was approved by the university’s institional review board. Parents and adolescents gave written consent and assent to participate, respectively. Actigraphy-based sleep data was collected during the school year. Adolescents wore actigraphs on their non-dominant wrists for seven consecutive nights. Nights with medication use were excluded from analyses. Families visited the lab 3.96 days (SD = 12.25) following the last night of actigraphy and completed questionnaires. Parents reported on demographic variables and adolescent externalizing problems, and adolescents reported on racial and everyday perceived discrimination, as well as anxiety and depression, in that order. Measures Perceived racial discrimination—Adolescents reported on their perceptions of racial/ ethnic discrimination using the 15-item Adolescent Discrimination Distress Index (Fisher et
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al., 2000). Adolescents were asked whether the following events (e.g., “you were hassled by a store clerk or store guard”; “you were discouraged from joining an advanced level of class”; “you were called racially insulting names”) happened to them because of their race or ethnicity, and if so, how much these events upset them. Items were rated on a 6-point scale (0 = does not apply to me; 1 = not at all upsetting to 5 = extremely upsetting). A total score was obtained by summing the responses across the 15 items (Fisher et al., 2000); α = . 90.
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Perceived everyday discrimination—Adolescents reported on perceptions of day-today discrimination using a modified 10-item version of the Everday Discrimination Scale (Williams et al., 1997; Guyll et al., 2001). Adolescents were asked how often each experience occurred in their day-to-day life (e.g., “you are treated with less respect than other people” and “people act as if they’re better than you are”). Items were rated on a 4point scale (1 = often to 4 = never). Responses were reverse coded and summed to create a total score where higher scores indicated greater discrimination (α = .86) (Williams et al., 2008). Adolescents also reported whether they attributed their overall experiences to each of the following domains (yes, no, or does not apply): language (< 5% reported yes), gender (10%), income (10%), religion (10%), race/ethnicity (16%), body weight (18%), physical appearance (26%), clothing (28%), age (34%), and whom they hang out with (46%).
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Sleep—Data were obtained using actigraphy (Motionlogger Octagonal Basic, Ambulatory Monitoring Inc., Ardsley, NY), and scored with the Sadeh algorithm (Sadeh et al., 1994). On average, 5.44 nights (SD = 1.77) of valid actigraphy data were available per adolescent. Sleep data for adolescents with fewer than five nights of actigraphy data (23%) were not included in analyses because of poor estimation of regular sleep (Meltzer et al., 2012). Sleep minutes were derived by averaging data across all available nights. Night-to-night stability during the week was adequate (α = .75). Adjustment—Adolescents completed the Revised Children’s Manifest Anxiety Scale 2 (RCMAS 2; Reynolds & Richmond, 2008). Two items regarding sleep were excluded (α = . 90). Further, youth completed the Children’s Depression Inventory (CDI; Kovacs, 1992). Two items regarding sleep were removed (α = .87). Additionally, adolescents completed the Externalizing scale of the Youth Self-Report (YSR; Achenbach & Rescorla, 2001).
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Controls—Sex (0 = girls, 1= boys), race/ethnicity (0 = EA, 1 = AA), family incometoneeds ratio, age, chronic illness (0 = no, 1= yes), and standardized BMI score (zBMI; Centers for Disease Control and Prevention, 2007) were controlled in analyses. Height and weight were measured in the laboratory. Plan of Analysis To reduce outlier effects, values of variables that exceeded 4 SDs were recoded as the highest or lowest observed value within 4 SDs. In total, three values were recoded, including one for perceived racial/ethnic discrimination and two for externalizing symptoms. A series of path models were fitted in AMOS (Arbuckle, 2012). Following current best practices, full information maximum likelihood (FIML) estimation was used to handle missing data, which
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allows for the use of all available data (Acock, 2005). Separate models were examined for the perceived racial and everyday discrimination measures. Control and predictor variables were mean-centered and significantly correlated exogenous variables were covaried. Sex, ethnicity, age, income-to-needs ratio, chronic illness, and zBMI were covaried. The main effects of discrimination and sleep minutes (rescaled by dividing sleep scores by 10 for easier interpretation of path coefficients) were entered in the models, followed by their interaction term. The Preacher et al. (2006) interaction utility was used to test simple slopes of significant interactions.
Results Preliminary Analyses
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On average, participants reported relatively low levels of perceived racial and everyday discrimination, obtained approximately seven hours of sleep per night, and were relatively well-adjusted (Table 1). Among demographic and primary study variables (not shown in Table 1), adolescents from higher socioeconomic status (SES) homes slept longer (r = .16, p < .05) and reported lower levels of racial discrimination (r = −.16, p < .05). Adolescents with chronic illness had shorter sleep duration (r = −.16, p < .05). Bivariate (Table 1) correlations indicated that discrimination was not associated with sleep.
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T-tests were conducted to examine sex and ethnic differences in study variables. In comparison to girls, boys had shorter sleep duration (Mboys = 391.99 minutes, SD = 53.36; Mgirls = 418.78 minutes, SD = 53.36; t = 3.49, p < .001) and reported lower levels of anxiety (Mboys = 7.03, SD = 7.31; Mgirls = 10.92, SD = 7.68; t = 3.98, p < .001) and depression (Mboys = 5.85, SD = 5.55; Mgirls = 7.77, SD = 6.15; t = 2.51, p < .05). Compared to AAs, EAs slept longer (MEA = 413.52 min, SD = 50.27; MAA = 387.97 min, SD = 61.93; t = 2.96, p < .01), and reported lower perceived racial discrimination (MEA =10.48, SD = 10.35; MAA = 20.20, SD = 13.22; t = −6.23, p < .001). Path Models Results from path models are presented in Table 2. Path coefficients reported are from the step of entry. Path models were a good fit to the data (non-significant χ2, root mean square error of approximation < .05, comparative fit index > .90). Perceived Racial Discrimination and Adjustment: Sleep as a Moderator
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Anxiety—In examining the effects of the covariates in the model (not depicted in the Tables for simplicity), boys reported lower levels of anxiety than girls (B = −3.87, SE = 1.01, β = −. 25, p < .001). Racial discrimination predicted higher levels of anxiety (Table 2). Central to this investigation, sleep moderated the effects of racial discrimination on anxiety and explained 3% of the unique variance in anxiety (total variance = 15.1%). Racial discrimination was related to anxiety among youth with longer sleep duration (B = .23, SE = .04, p < .001), but not among those with shorter sleep duration (B = .01, SE = .04, p = . 77).
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As shown in Figure 1a, youth with shorter sleep duration had relatively high levels of anxiety regardless of discrimination (M = 12.37 at low and 12.70 at high discrimination). At low levels of discrimination, youth with longer sleep duration had lower predicted levels of anxiety compared to those with shorter sleep duration (Ms = 8.07 and 13.78, respectively), a difference of .74 SD. Adolescents with the lowest risk for anxiety were those with longer sleep duration in conjunction with low levels of discrimination (M = 8.07). Note that adolescents who slept longer (+1 SD) obtained 7.69 hours of sleep; those with shorter sleep obtained 5.86 hours.
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Depression—Examination of the covariates indicated that boys reported lower levels of depressive symptoms than girls (B = −1.97, SE = .79, β = −.17, p < .001). Racial discrimination was associated with higher levels of depressive symptoms. Further, sleep duration moderated the effects of discrimination on depressive symptoms and explained 3% of the unique variance in depression (total variance = 16.5%). Tests of simple slopes revealed that discrimination predicted depression for youth with longer but not shorter sleep duration (B = .20, SE = .03, p < .001; B = .05, SE = .03, p = .11; respectively; Figure 1b),. At low levels of overall racial discrimination, in comparison to adolescents with longer sleep duration, those with shorter sleep duration had higher levels of depressive symptoms (Ms = 9.38 and 5.04, respectively), a difference of .73 SD. At high levels of discrimination, youth had similar levels of depression regardless of sleep (M = 10.63 for short sleepers, and M = 10.07 for longer sleepers). Further, youth with the lowest predicted levels of depressive symptoms were those with longer sleep in combination with lower levels of perceived discrimination (M = 5.04).
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Externalizing—High SES was related to lower externalizing symptoms (B = −.94, SE = . 42, β = −.16, p < .05). Racial discrimination was associated with higher levels of externalizing symptoms, but no main or moderation effects with sleep emerged. This model explained 16.1% of the variance in externalizing symptoms. Perceived Everyday Discrimination and Adjustment: Sleep as a Moderator Anxiety and depression—Everyday discrimination was associated with higher levels of anxiety and depressive symptoms. No moderation effects were observed. These models explained 31.4% and 35.1% of the variance in anxiety and depression, respectively.
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Externalizing—Everyday discrimination was associated with externalizing symptoms and sleep duration moderated this relation (Figure 2); the interaction effect explained 2% of unique variance (total variance = 21.1%). The association was significant for youth with shorter (B = .81, SE = .09, p < .001) and longer (B = .38, SE = .09, p < .001) sleep yet appears somewhat stronger for the former. At lower levels of discrimination, youth with shorter and longer sleep durations had relatively similar levels of externalizing behaviors (Ms = 7.30 and 8.99, respectively). Differences in externalizing problems between adolescents with shorter and longer sleep were more evident at high levels of discrimination (Ms = 16.05 and 13.12, respectively).
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Exploratory analyses examining two- and three-way interactions among discrimination, sleep, and either ethnicity, sex, or SES yielded mostly null effects with no clear pattern of effects. No significant interactions emerged for ethnicity, 1 out of 6 interactions emerged for sex, and 2 out of 6 interactions emerged for SES; thus, these were not considered further. To ensure that the percentage of missing data for sleep minutes (23%), which is not atypical, did not have much bearing on results, additional analyses were conducted with the subsample that had valid actigraphy data (5 or more nights; n = 193). These models yielded equivalent findings to those presented in the main analyses with the full sample of 252 participants, with the only notable difference being that one moderation effect was at the trend level.
Discussion Author Manuscript
Perceived discrimination has a harmful effect on the psychological adjustment of adolescents (Schmitt et al., 2014), but its consequences are not uniform (Greene et al., 2006). Building on recent research, we examined sleep duration as a moderator of the association between perceived discrimination and mental health. Results illustrate that longer sleep duration may confer protection and shorter sleep duration may increase vulnerability for adjustment problems for individuals faced with perceived discrimination.
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Congruent with previous research, measures of discrimination were associated with internalizing and externalizing behavior problems. Building on the literature, perceived racial discrimination interacted with sleep to predict anxiety and depressive symptoms. Generally, adolescents with shorter sleep tended to have higher levels of internalizing symptoms regardless of discrimination. For youth who slept longer, the expected positive association between ethnic discrimination and internalizing symptoms was evident. For these youth, the subset with higher levels of discrimination had relatively high levels of internalizing symptoms. However, those with longer sleep and lower levels of discrimination had the lowest levels of internalizing symptoms. Thus, the benefit of longer sleep is not present for those with higher levels of discrimination. Anxiety and depression are highly correlated constructs, and the similar pattern of effects across these two outcomes may be due in part to shared variance.
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These findings are consistent with some literature on the moderating role of sleep in various contexts (Bordeleau et al., 2012) and support a dual-protection or protective-reactive pattern of effects (Luthar et al., 2000). Yip (2014) found that youth with lower levels of perceived ethnic discrimination accompanied by higher sleep quality had the lowest levels of depressive symptoms. Those with higher levels of discrimination and poor sleep had higher depressive symptoms, which can be construed as quite similar to our findings. Yip did not find effects for sleep duration (reported sleep period). In the present study, the number of minutes during which youth were asleep was assessed, which may account for some of the differential effects. For perceptions of everyday discrimination, frequently endorsed domains pertained to who adolescents hang out with, age, clothing, physical appearance, body weight, and race/
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ethnicity, in this order. With respect to the association between general everyday discrimination and externalizing behaviors, moderation findings indicate a different pattern of effects consistent with the interpretation of longer sleep as a protective factor. Specifically, the effects of discrimination on externalizing behaviors were present at all levels of sleep duration, but were exacerbated when sleep was short, in line with a dual-risk framework. This is consistent with research showing higher levels of externalizing symptoms among children with short sleep durations (Kelly & El-Sheikh, 2014), and suggests that this may be particularly the case at higher levels of stress exposure.
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It is not clear why different patterns of effects emerged for the two discrimination domains in conjunction with various outcome measures. Previous research suggests that both types of discrimination examined are linked to mental health. However, there is also evidence that they may assess distinct aspects of discrimination (Chae et al., 2008; Lewis et al., 2015). For example, being prompted to report experiences of racial discrimination versus general unfair treatment may lead individuals to recollect different sets of experiences. Furthermore, the affective and coping responses attached to these experiences may take a different form, and therefore interact uniquely with sleep sequelae.
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Sleep insufficiency has a negative impact on the experience and processing of emotions (Baum et al., 2014; Soffer-Dudek et al., 2011; Walker & van Der Helm, 2009), which could contribute to adjustment problems. Path models supported direct associations between sleep duration and only depression. Nevertheless, moderation effects involving discrimination and sleep were found for all adjustment outcomes indicating that sleep could alter relations between risk factors and adjustment outcomes. Although we examined sleep as the moderator of effects, graphs could be interpreted as supportive of sleep as the predictor of adjustment outcomes with perceived discrimination as the moderator. The take home message of this scenario is similar to that of the present findings: adolescents at the least risk for maladjustment are those with longer sleep duration in conjunction with lower levels of discrimination.
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Several limitations warrant mention. Although the full models explained large percentages of the variance in youths’ adjustment, the moderation effects accounted for a modest amount of variance, which is consistent with much of those reported in the pertinent literatures. Participants were European and African Americans from rural and semi-rural Alabama and many were economically disadvantaged. Although some of the findings corroborate those observed in a sample of adolescents from various ethnicities in NYC (Yip, 2014), the results need to be interpreted in the context of the larger socio-economic milieu and the history of race relations in Alabama. Given that the sample was composed of relatively well-adjusted youth, who slept on average for 6.8 hours, findings would likely be more pronounced in clinical samples. While acknowledging study boundaries, this investigation provides evidence that sleep duration moderates associations linking perceived general and racial discrimination with internalizing and externalizing behaviors, and sheds some light on variables that may affect youths’ adjustment in the context of such stress experiences.
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Acknowledgments This research was supported by Grant R01-HD046795 from the Eunice Kennedy Shriver National Institute of Child Health and Human Development awarded to Mona El-Sheikh. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. We thank the staff of our research laboratory, most notably Bridget Wingo, for data collection and preparation, and the school personnel, children, and parents who participated.
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Figure 1.
Sleep minutes moderating the association linking perceived racial/ethnic discrimination with anxiety and depression.
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Figure 2.
Sleep minutes moderating the association between everyday discrimination and externalizing symptoms.
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Author Manuscript .40**
.32**
6. Externalizing
0–63
10–35
239.40–543.14
406.37 (54.84)
−.06
−.14
−.03
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3
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.34**
.75**
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4
0–29
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.48**
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5
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10.45 (7.91)
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6
p < .05.
*
p < .01.
**
Derived from the Daily Life Experiences questionnaire.
b
a Derived from the Adolescent Discrimination Distress Index.
Note. Partial correlations controlling for sex, race/ethnicity, age, income-to-needs ratio, chronic illness, and standardized body mass index did not reveal correlations between measures of discrimination and sleep duration.
Range
16.63 (5.40)
.53**
.23**
5. Depression
13.80 (12.31)
.46**
.15*
4. Anxiety
Mean (SD)
−.05
−.11
3. Sleep minutes
-
.54**
-
2
2. Everyday discriminationb
1. Racial/ethnic discriminationa
1
Descriptive Statistics and Correlations among Perceived Discrimination, Sleep, and Adolescent Adjustment
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Table 1 El-Sheikh et al. Page 13
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Author Manuscript −.12 (.91) .03 (.02)
Sleep minutes
Discrimination x Sleep minutes
.10
−.09
31.4%
15.1%
R2
−.06
−.18**
−.19 (.07)** −.01 (.01)
.54***
.15*
−.21**
.26***
β
.60 (.06)***
.01 (.01)*
−.22 (.08)**
.13 (.03)***
B (SE)
Depression
35.1%
16.5%
R2
−.04 −.14*
−.04 (.02)*
.41***
.07
−.03
.37***
β
−.06 (.10)
.60 (.09)***
.01 (.01)
−.05 (.11)
.24 (.04)***
B (SE)
Externalizing
21.1%
16.1%
R2
p < .001.
p < .01.
***
**
p < .05.
*
Derived from the Daily Life Experiences questionnaire. Sleep was rescaled so that coefficients could be more easily interpreted (scores divided by 10).
b
a Derived from the Adolescent Discrimination Distress Index.
Note. Path models controlled for sex, ethnicity, age, income-to-needs, chronic illness, and zBMI (not shown). Path coefficients reported are from the step of entry. R2 reported is from the final model.
.68 (.08)***
Discrimination
.47***
.16*
.02 (.01)*
Discrimination x Sleep minutes
Everyday Discriminationb
−.10
.19**
−.15 (.10)
.12 (.04)**
β
Sleep minutes
Discrimination
Racial/Ethnic Discriminationa
B (SE)
Anxiety
Path Coefficients for Associations Linking Perceived Discrimination, Sleep, and Adjustment
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J Sleep Res. Author manuscript; available in PMC 2017 February 01. Published in final edited form as: J Sleep Res. 2016 February ; 25(1): 70–77. doi:10.1111/jsr.12333.
Perceived Discrimination and Youths’ Adjustment: Sleep as a Moderator Mona El-Sheikha, Kelly M. Tua, Ekjyot K. Sainia, Thomas E. Fuller-Rowella, and Joseph A. Buckhaltb
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aDepartment
of Human Development and Family Studies, Auburn University, AL
bDepartment
of Special Education, Rehabilitation and Counseling, Auburn University, AL
Summary
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Adolescents’ sleep duration was examined as a moderator of the association between perceived discrimination and internalizing (anxiety, depression) and externalizing symptoms. Participants were 252 adolescents (M = 15.79 years; 66% European American, 34% African American) who reported on their perceived discrimination (racial and general) and adjustment. Sleep duration was measured using actigraphy. Moderation effects were evident. The lowest levels of internalizing symptoms were observed for adolescents with longer sleep duration in conjunction with lower levels of perceived racial discrimination. Further, general perceived discrimination was more strongly associated with externalizing behaviors for youth with shorter versus longer sleep. Findings highlight the importance of sleep as a bioregulatory system that can ameliorate or exacerbate the effects of discrimination on youths’ adjustment.
Keywords racial discrimination; general discrimination; actigraphy; internalizing; externalizing
Introduction
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Perceived discrimination is a risk factor for psychological problems in children and adults (for reviews see Williams & Mohammed, 2013 and Schmitt et al., 2014). In particular, studies have found associations with externalizing symptoms (Coker et al., 2009; FullerRowell et al., 2011), as well as with depression and anxiety (Greene et al., 2006; Yip, 2014). However, these effects are not uniform (Greene et al., 2006; Schmitt et al., 2014), and vulnerability and protective factors have been identified. Sleep is an important bioregulatory system that underlies emotional and behavioral regulation (Baum et al., 2014; Dahl, 1996). Yet, few studies have examined sleep as a moderator that may ameliorate or amplify the effects of perceived discrimination on youths’ adjustment. The current study addresses this gap in the literature.
Correspondence: Mona El-Sheikh, Ph.D., Human Development and Family Studies, 203 Spidle Hall, Auburn University, Auburn, AL 36849-5214; Tel: 1-334-844-3294, Fax: 1-334-844-4515, [email protected]. Conflicts of interest: There are no conflicts of interest. Author contributorship: All authors contributed in a meaningful way to this manuscript.
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Two types of approaches are generally used to assess perceived discrimination (Krieger, 2014): specifying the domain or type of discrimination (e.g., racial/ethnic) (Fisher et al., 2000) or general reports of unfair treatment across a broader range of possible events (Krieger et al., 2005; Williams et al., 1997). For general unfair treatment, follow-up questions are sometimes used to specify one or more possible attributions. Both approaches have been commonly used and have demonstrated predictive validity in both African American (AA) and European American (EA) samples (e.g., Fuller-Rowell et al., 2012; Sellers et al., 2003). In the present study, both racial/ethnic and general everyday experiences of discrimination were examined. Racial/ethnic discrimination is defined as “perceptions of unfair treatment on the basis of one’s race/ethnicity”. General everyday discrimination refers to “perceptions of unfair treatment” and does not require an attribution to a specific personal characteristic.
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Some evidence, albeit scarce, has linked perceived discrimination with poor subjective sleep quality in youth (Huynh & Gillen-O’Neel, 2013). Sleep insufficiency is associated with increased negative emotions and emotion regulation difficulties (Baum, 2014), as well as internalizing and externalizing problems in youth (Kelly & El-Sheikh, 2014). Sleep problems may contribute to adjustment problems through their effects on brain processes critical for emotion and behavioral regulation (Dahl, 1996).
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To our knowledge, only one study has examined the moderating influence of sleep in the context of discrimination (Yip, 2014). In an adolescent sample, self-reported sleep quality, but not sleep period (bedtime to wake time), moderated the effects of racial/ethnic discrimination on depressive symptoms. High levels of perceived racial/ethnic discrimination accompanied by poor sleep quality was prospectively associated with depressive symptoms. Further, adolescents with the lowest depression were those with low discrimination in conjunction with better sleep. Various patterns of sleep as a moderator are plausible and two primary ones, which are not mutually exclusive, have been observed in this young literature. Several studies have yielded a moderation pattern of effects that is consistent with cumulative or dual risk risk perspectives (Evans, 2003; Sameroff, 1983), which propose that individuals may have a vulnerability that increases risk, or a protective factor that reduces risk, in the context of of an environmental stressor. For instance, short or poor quality sleep increased vulnerability for adjustment problems, whereas better sleep quality functioned as a protective factor, in the context of family and peer stress (Lemola et al., 2012; Tu et al., 2015).
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Findings from other studies have revealed a dual-protection or protective-reactive pattern of effects (Luthar et al., 2000), in which a protective attribute (better sleep) is benefical in low but not high risk contexts. Supportive of this pattern, children and adolescents with the highest level of adaptation were those with longer and better quality sleep in conjuction with low familial (Bernier et al., 2014; Bordeleau et al., 2012; El-Sheikh et al., 2014), peer (Tu et al., 2015), or socio-cultural risks (Yip, 2014). The present investigation examined actigraphy-based sleep minutes in relation to two domains of perceived discrimination (racial/ethnic and general unfair treatment) in the
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prediction of internalizing and externalizing behaviors in a sample of adolescents from predominantly rural and semi-rural Alabama. With evidence of dual-risk and dual-protection effects emerging in the literature on sleep as a moderator, it is possible that shorter sleep may increase risk and longer sleep may ameliorate risk in the association between discrimination and adjustment problems. It is also plausible that longer sleep may be protective against maladjustment in the context of low discrimination, but not high discrimination. Nevertheless, it is also possible that other moderation effects could emerge and our main objective was the identification of sleep as a moderator of risk and explicating the pattern of such effects.
Method Participants
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Data for the current study comes from the fourth wave (collected from 2012–2013) of the Family Stress Study conducted at Auburn University; neither the discrimination measures nor actigraphy data were collected at the earlier waves. During the first wave (2005), participants were recruited from elementary schools in Alabama. Children were from two parent homes and did not have a diagnosis of attention deficit hyperactivity disorder, developmental delays, or a chronic illness. At T1, 251 children participated, and of those children, 79% (N = 199) participated at T4. To increase sample size, an additional 53 youth were recruited for the present wave using the same inclusion criteria, and from the same schools as the original sample. No differences across study variables emerged between participants recruited at T1 versus T4.
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The full analytic sample was composed of 252 adolescents (118 boys, 134 girls, 66% European American (AA), 34% African American (AA) between the ages of 14 and 18 (M age = 15.79 years, SD = .81). The ethnic/racial composition of the sample is representative of the area. Family income-to-needs ratio (annual family income divided by the poverty threshold considering the family size; U.S. Department of Commerce, 2013) indicated that ~ 42% of families were living below or near the poverty line (ratio < 2) and 36% were middle class (ratio ≥ 3). Procedure
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The study was approved by the university’s institional review board. Parents and adolescents gave written consent and assent to participate, respectively. Actigraphy-based sleep data was collected during the school year. Adolescents wore actigraphs on their non-dominant wrists for seven consecutive nights. Nights with medication use were excluded from analyses. Families visited the lab 3.96 days (SD = 12.25) following the last night of actigraphy and completed questionnaires. Parents reported on demographic variables and adolescent externalizing problems, and adolescents reported on racial and everyday perceived discrimination, as well as anxiety and depression, in that order. Measures Perceived racial discrimination—Adolescents reported on their perceptions of racial/ ethnic discrimination using the 15-item Adolescent Discrimination Distress Index (Fisher et
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al., 2000). Adolescents were asked whether the following events (e.g., “you were hassled by a store clerk or store guard”; “you were discouraged from joining an advanced level of class”; “you were called racially insulting names”) happened to them because of their race or ethnicity, and if so, how much these events upset them. Items were rated on a 6-point scale (0 = does not apply to me; 1 = not at all upsetting to 5 = extremely upsetting). A total score was obtained by summing the responses across the 15 items (Fisher et al., 2000); α = . 90.
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Perceived everyday discrimination—Adolescents reported on perceptions of day-today discrimination using a modified 10-item version of the Everday Discrimination Scale (Williams et al., 1997; Guyll et al., 2001). Adolescents were asked how often each experience occurred in their day-to-day life (e.g., “you are treated with less respect than other people” and “people act as if they’re better than you are”). Items were rated on a 4point scale (1 = often to 4 = never). Responses were reverse coded and summed to create a total score where higher scores indicated greater discrimination (α = .86) (Williams et al., 2008). Adolescents also reported whether they attributed their overall experiences to each of the following domains (yes, no, or does not apply): language (< 5% reported yes), gender (10%), income (10%), religion (10%), race/ethnicity (16%), body weight (18%), physical appearance (26%), clothing (28%), age (34%), and whom they hang out with (46%).
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Sleep—Data were obtained using actigraphy (Motionlogger Octagonal Basic, Ambulatory Monitoring Inc., Ardsley, NY), and scored with the Sadeh algorithm (Sadeh et al., 1994). On average, 5.44 nights (SD = 1.77) of valid actigraphy data were available per adolescent. Sleep data for adolescents with fewer than five nights of actigraphy data (23%) were not included in analyses because of poor estimation of regular sleep (Meltzer et al., 2012). Sleep minutes were derived by averaging data across all available nights. Night-to-night stability during the week was adequate (α = .75). Adjustment—Adolescents completed the Revised Children’s Manifest Anxiety Scale 2 (RCMAS 2; Reynolds & Richmond, 2008). Two items regarding sleep were excluded (α = . 90). Further, youth completed the Children’s Depression Inventory (CDI; Kovacs, 1992). Two items regarding sleep were removed (α = .87). Additionally, adolescents completed the Externalizing scale of the Youth Self-Report (YSR; Achenbach & Rescorla, 2001).
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Controls—Sex (0 = girls, 1= boys), race/ethnicity (0 = EA, 1 = AA), family incometoneeds ratio, age, chronic illness (0 = no, 1= yes), and standardized BMI score (zBMI; Centers for Disease Control and Prevention, 2007) were controlled in analyses. Height and weight were measured in the laboratory. Plan of Analysis To reduce outlier effects, values of variables that exceeded 4 SDs were recoded as the highest or lowest observed value within 4 SDs. In total, three values were recoded, including one for perceived racial/ethnic discrimination and two for externalizing symptoms. A series of path models were fitted in AMOS (Arbuckle, 2012). Following current best practices, full information maximum likelihood (FIML) estimation was used to handle missing data, which
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allows for the use of all available data (Acock, 2005). Separate models were examined for the perceived racial and everyday discrimination measures. Control and predictor variables were mean-centered and significantly correlated exogenous variables were covaried. Sex, ethnicity, age, income-to-needs ratio, chronic illness, and zBMI were covaried. The main effects of discrimination and sleep minutes (rescaled by dividing sleep scores by 10 for easier interpretation of path coefficients) were entered in the models, followed by their interaction term. The Preacher et al. (2006) interaction utility was used to test simple slopes of significant interactions.
Results Preliminary Analyses
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On average, participants reported relatively low levels of perceived racial and everyday discrimination, obtained approximately seven hours of sleep per night, and were relatively well-adjusted (Table 1). Among demographic and primary study variables (not shown in Table 1), adolescents from higher socioeconomic status (SES) homes slept longer (r = .16, p < .05) and reported lower levels of racial discrimination (r = −.16, p < .05). Adolescents with chronic illness had shorter sleep duration (r = −.16, p < .05). Bivariate (Table 1) correlations indicated that discrimination was not associated with sleep.
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T-tests were conducted to examine sex and ethnic differences in study variables. In comparison to girls, boys had shorter sleep duration (Mboys = 391.99 minutes, SD = 53.36; Mgirls = 418.78 minutes, SD = 53.36; t = 3.49, p < .001) and reported lower levels of anxiety (Mboys = 7.03, SD = 7.31; Mgirls = 10.92, SD = 7.68; t = 3.98, p < .001) and depression (Mboys = 5.85, SD = 5.55; Mgirls = 7.77, SD = 6.15; t = 2.51, p < .05). Compared to AAs, EAs slept longer (MEA = 413.52 min, SD = 50.27; MAA = 387.97 min, SD = 61.93; t = 2.96, p < .01), and reported lower perceived racial discrimination (MEA =10.48, SD = 10.35; MAA = 20.20, SD = 13.22; t = −6.23, p < .001). Path Models Results from path models are presented in Table 2. Path coefficients reported are from the step of entry. Path models were a good fit to the data (non-significant χ2, root mean square error of approximation < .05, comparative fit index > .90). Perceived Racial Discrimination and Adjustment: Sleep as a Moderator
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Anxiety—In examining the effects of the covariates in the model (not depicted in the Tables for simplicity), boys reported lower levels of anxiety than girls (B = −3.87, SE = 1.01, β = −. 25, p < .001). Racial discrimination predicted higher levels of anxiety (Table 2). Central to this investigation, sleep moderated the effects of racial discrimination on anxiety and explained 3% of the unique variance in anxiety (total variance = 15.1%). Racial discrimination was related to anxiety among youth with longer sleep duration (B = .23, SE = .04, p < .001), but not among those with shorter sleep duration (B = .01, SE = .04, p = . 77).
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As shown in Figure 1a, youth with shorter sleep duration had relatively high levels of anxiety regardless of discrimination (M = 12.37 at low and 12.70 at high discrimination). At low levels of discrimination, youth with longer sleep duration had lower predicted levels of anxiety compared to those with shorter sleep duration (Ms = 8.07 and 13.78, respectively), a difference of .74 SD. Adolescents with the lowest risk for anxiety were those with longer sleep duration in conjunction with low levels of discrimination (M = 8.07). Note that adolescents who slept longer (+1 SD) obtained 7.69 hours of sleep; those with shorter sleep obtained 5.86 hours.
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Depression—Examination of the covariates indicated that boys reported lower levels of depressive symptoms than girls (B = −1.97, SE = .79, β = −.17, p < .001). Racial discrimination was associated with higher levels of depressive symptoms. Further, sleep duration moderated the effects of discrimination on depressive symptoms and explained 3% of the unique variance in depression (total variance = 16.5%). Tests of simple slopes revealed that discrimination predicted depression for youth with longer but not shorter sleep duration (B = .20, SE = .03, p < .001; B = .05, SE = .03, p = .11; respectively; Figure 1b),. At low levels of overall racial discrimination, in comparison to adolescents with longer sleep duration, those with shorter sleep duration had higher levels of depressive symptoms (Ms = 9.38 and 5.04, respectively), a difference of .73 SD. At high levels of discrimination, youth had similar levels of depression regardless of sleep (M = 10.63 for short sleepers, and M = 10.07 for longer sleepers). Further, youth with the lowest predicted levels of depressive symptoms were those with longer sleep in combination with lower levels of perceived discrimination (M = 5.04).
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Externalizing—High SES was related to lower externalizing symptoms (B = −.94, SE = . 42, β = −.16, p < .05). Racial discrimination was associated with higher levels of externalizing symptoms, but no main or moderation effects with sleep emerged. This model explained 16.1% of the variance in externalizing symptoms. Perceived Everyday Discrimination and Adjustment: Sleep as a Moderator Anxiety and depression—Everyday discrimination was associated with higher levels of anxiety and depressive symptoms. No moderation effects were observed. These models explained 31.4% and 35.1% of the variance in anxiety and depression, respectively.
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Externalizing—Everyday discrimination was associated with externalizing symptoms and sleep duration moderated this relation (Figure 2); the interaction effect explained 2% of unique variance (total variance = 21.1%). The association was significant for youth with shorter (B = .81, SE = .09, p < .001) and longer (B = .38, SE = .09, p < .001) sleep yet appears somewhat stronger for the former. At lower levels of discrimination, youth with shorter and longer sleep durations had relatively similar levels of externalizing behaviors (Ms = 7.30 and 8.99, respectively). Differences in externalizing problems between adolescents with shorter and longer sleep were more evident at high levels of discrimination (Ms = 16.05 and 13.12, respectively).
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Exploratory analyses examining two- and three-way interactions among discrimination, sleep, and either ethnicity, sex, or SES yielded mostly null effects with no clear pattern of effects. No significant interactions emerged for ethnicity, 1 out of 6 interactions emerged for sex, and 2 out of 6 interactions emerged for SES; thus, these were not considered further. To ensure that the percentage of missing data for sleep minutes (23%), which is not atypical, did not have much bearing on results, additional analyses were conducted with the subsample that had valid actigraphy data (5 or more nights; n = 193). These models yielded equivalent findings to those presented in the main analyses with the full sample of 252 participants, with the only notable difference being that one moderation effect was at the trend level.
Discussion Author Manuscript
Perceived discrimination has a harmful effect on the psychological adjustment of adolescents (Schmitt et al., 2014), but its consequences are not uniform (Greene et al., 2006). Building on recent research, we examined sleep duration as a moderator of the association between perceived discrimination and mental health. Results illustrate that longer sleep duration may confer protection and shorter sleep duration may increase vulnerability for adjustment problems for individuals faced with perceived discrimination.
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Congruent with previous research, measures of discrimination were associated with internalizing and externalizing behavior problems. Building on the literature, perceived racial discrimination interacted with sleep to predict anxiety and depressive symptoms. Generally, adolescents with shorter sleep tended to have higher levels of internalizing symptoms regardless of discrimination. For youth who slept longer, the expected positive association between ethnic discrimination and internalizing symptoms was evident. For these youth, the subset with higher levels of discrimination had relatively high levels of internalizing symptoms. However, those with longer sleep and lower levels of discrimination had the lowest levels of internalizing symptoms. Thus, the benefit of longer sleep is not present for those with higher levels of discrimination. Anxiety and depression are highly correlated constructs, and the similar pattern of effects across these two outcomes may be due in part to shared variance.
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These findings are consistent with some literature on the moderating role of sleep in various contexts (Bordeleau et al., 2012) and support a dual-protection or protective-reactive pattern of effects (Luthar et al., 2000). Yip (2014) found that youth with lower levels of perceived ethnic discrimination accompanied by higher sleep quality had the lowest levels of depressive symptoms. Those with higher levels of discrimination and poor sleep had higher depressive symptoms, which can be construed as quite similar to our findings. Yip did not find effects for sleep duration (reported sleep period). In the present study, the number of minutes during which youth were asleep was assessed, which may account for some of the differential effects. For perceptions of everyday discrimination, frequently endorsed domains pertained to who adolescents hang out with, age, clothing, physical appearance, body weight, and race/
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ethnicity, in this order. With respect to the association between general everyday discrimination and externalizing behaviors, moderation findings indicate a different pattern of effects consistent with the interpretation of longer sleep as a protective factor. Specifically, the effects of discrimination on externalizing behaviors were present at all levels of sleep duration, but were exacerbated when sleep was short, in line with a dual-risk framework. This is consistent with research showing higher levels of externalizing symptoms among children with short sleep durations (Kelly & El-Sheikh, 2014), and suggests that this may be particularly the case at higher levels of stress exposure.
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It is not clear why different patterns of effects emerged for the two discrimination domains in conjunction with various outcome measures. Previous research suggests that both types of discrimination examined are linked to mental health. However, there is also evidence that they may assess distinct aspects of discrimination (Chae et al., 2008; Lewis et al., 2015). For example, being prompted to report experiences of racial discrimination versus general unfair treatment may lead individuals to recollect different sets of experiences. Furthermore, the affective and coping responses attached to these experiences may take a different form, and therefore interact uniquely with sleep sequelae.
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Sleep insufficiency has a negative impact on the experience and processing of emotions (Baum et al., 2014; Soffer-Dudek et al., 2011; Walker & van Der Helm, 2009), which could contribute to adjustment problems. Path models supported direct associations between sleep duration and only depression. Nevertheless, moderation effects involving discrimination and sleep were found for all adjustment outcomes indicating that sleep could alter relations between risk factors and adjustment outcomes. Although we examined sleep as the moderator of effects, graphs could be interpreted as supportive of sleep as the predictor of adjustment outcomes with perceived discrimination as the moderator. The take home message of this scenario is similar to that of the present findings: adolescents at the least risk for maladjustment are those with longer sleep duration in conjunction with lower levels of discrimination.
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Several limitations warrant mention. Although the full models explained large percentages of the variance in youths’ adjustment, the moderation effects accounted for a modest amount of variance, which is consistent with much of those reported in the pertinent literatures. Participants were European and African Americans from rural and semi-rural Alabama and many were economically disadvantaged. Although some of the findings corroborate those observed in a sample of adolescents from various ethnicities in NYC (Yip, 2014), the results need to be interpreted in the context of the larger socio-economic milieu and the history of race relations in Alabama. Given that the sample was composed of relatively well-adjusted youth, who slept on average for 6.8 hours, findings would likely be more pronounced in clinical samples. While acknowledging study boundaries, this investigation provides evidence that sleep duration moderates associations linking perceived general and racial discrimination with internalizing and externalizing behaviors, and sheds some light on variables that may affect youths’ adjustment in the context of such stress experiences.
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Acknowledgments This research was supported by Grant R01-HD046795 from the Eunice Kennedy Shriver National Institute of Child Health and Human Development awarded to Mona El-Sheikh. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. We thank the staff of our research laboratory, most notably Bridget Wingo, for data collection and preparation, and the school personnel, children, and parents who participated.
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Figure 1.
Sleep minutes moderating the association linking perceived racial/ethnic discrimination with anxiety and depression.
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Figure 2.
Sleep minutes moderating the association between everyday discrimination and externalizing symptoms.
Author Manuscript Author Manuscript J Sleep Res. Author manuscript; available in PMC 2017 February 01.
Author Manuscript
Author Manuscript
Author Manuscript .40**
.32**
6. Externalizing
0–63
10–35
239.40–543.14
406.37 (54.84)
−.06
−.14
−.03
-
3
0–31
9.08 (7.74)
.34**
.75**
-
4
0–29
6.86 (5.94)
.48**
-
5
0–39
10.45 (7.91)
-
6
p < .05.
*
p < .01.
**
Derived from the Daily Life Experiences questionnaire.
b
a Derived from the Adolescent Discrimination Distress Index.
Note. Partial correlations controlling for sex, race/ethnicity, age, income-to-needs ratio, chronic illness, and standardized body mass index did not reveal correlations between measures of discrimination and sleep duration.
Range
16.63 (5.40)
.53**
.23**
5. Depression
13.80 (12.31)
.46**
.15*
4. Anxiety
Mean (SD)
−.05
−.11
3. Sleep minutes
-
.54**
-
2
2. Everyday discriminationb
1. Racial/ethnic discriminationa
1
Descriptive Statistics and Correlations among Perceived Discrimination, Sleep, and Adolescent Adjustment
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Table 1 El-Sheikh et al. Page 13
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Author Manuscript
Author Manuscript −.12 (.91) .03 (.02)
Sleep minutes
Discrimination x Sleep minutes
.10
−.09
31.4%
15.1%
R2
−.06
−.18**
−.19 (.07)** −.01 (.01)
.54***
.15*
−.21**
.26***
β
.60 (.06)***
.01 (.01)*
−.22 (.08)**
.13 (.03)***
B (SE)
Depression
35.1%
16.5%
R2
−.04 −.14*
−.04 (.02)*
.41***
.07
−.03
.37***
β
−.06 (.10)
.60 (.09)***
.01 (.01)
−.05 (.11)
.24 (.04)***
B (SE)
Externalizing
21.1%
16.1%
R2
p < .001.
p < .01.
***
**
p < .05.
*
Derived from the Daily Life Experiences questionnaire. Sleep was rescaled so that coefficients could be more easily interpreted (scores divided by 10).
b
a Derived from the Adolescent Discrimination Distress Index.
Note. Path models controlled for sex, ethnicity, age, income-to-needs, chronic illness, and zBMI (not shown). Path coefficients reported are from the step of entry. R2 reported is from the final model.
.68 (.08)***
Discrimination
.47***
.16*
.02 (.01)*
Discrimination x Sleep minutes
Everyday Discriminationb
−.10
.19**
−.15 (.10)
.12 (.04)**
β
Sleep minutes
Discrimination
Racial/Ethnic Discriminationa
B (SE)
Anxiety
Path Coefficients for Associations Linking Perceived Discrimination, Sleep, and Adjustment
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Table 2 El-Sheikh et al. Page 14
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