Sleep, psychopathology and cultural diversity

Abstract

Research on ethnic/racial disparities in sleep in the United States finds minorities to have shorter self-reported and actigraphy-recorded sleep duration and poorer sleep quality. Disparities in mental health mirror disparities in sleep with ethnic/racial minorities reporting higher prevalence and more severe struggles. This review focuses on recent research in sleep and mental health disparities and considers ethnic/racial discrimination as an important third variable that may link these two domains of disparities research. For example, research has found discrimination to mediate ethnic/racial disparities in sleep; at the same time, sleep has been observed to mediate the link between discrimination and mental health. The review concludes with the importance of considering ethnicity/race and accompanying sociodemographic, environmental, and behavioral influences on sleep and mental health research.

The intersection of sleep, psychopathology, and diversity occupy a critical nexus in the science of health disparities; sleep and mental health are both areas in which ethnic/racial disparities are apparent. Although disparities in mental health have been the subject of more research and are better established, there is a growing literature observing similar disparities in sleep. Simply put, ethnic/racial minorities suffer shorter sleep duration and poorer sleep quality than their White counterparts. While sleep disparities have been most widely observed among adult samples [1], there is increasing evidence to suggest that ethnic/racial disparities in sleep are evident in early childhood and adolescence [2]. In an effort to reduce disparities, scholars have begun to unpack sociodemographic and environmental influences on sleep disparities. Recognizing the importance of sleep for daily functioning as well as longer-term health, we review cross-sectional and longitudinal connections between disparities in sleep and psychopathology, while also considering sociodemographic and environmental correlates of sleep and mental health disparities.

Ethnic/racial differences in sleep

Relative to White individuals, research finds that ethnic/racial minorities have shorter sleep duration and poorer sleep quality in the United States [2,3]. Disparities are apparent as early as infancy, continue through childhood, and persist through adulthood [4,5••]. Moreover, racial disparities in sleep are apparent across self-reported measures, polysomnography, as well as actigraphy-recorded sleep [6–8]. The magnitude of the disparities between ethnic/racial minorities and Whites is not negligible. Black adults are five times more likely to report sleeping less than 6 hours, 1.6 times more likely to exhibit poor sleep efficiency, and nearly twice as likely to report daytime sleepiness [9]. There are also racial disparities in sleep architecture, where Black adults (age 19–53) exhibit more light sleep and less deep (slow wave) sleep compared to White adults [3]. Racial disparities are not only apparent between Black and White adults, Latinx adults also have notable sleep disparities including being twice as likely to sleep less than 6 hours per night, 1.4 times more likely to exhibit poor sleep efficiency, and 1.2 times more likely to report daytime sleepiness. Finally, research on Asian Americans finds similar patterns of disparities [9]. Specifically, Chinese adults appear to be 2.3 times more likely to report sleeping less than 6 hours per night, and were nearly twice as likely to exhibit poor sleep efficiency compared to White adults [9]. Similarly patterned disparities have also been observed in childhood. In a regionally representative study of 6–12 year old children in New York City, researchers found that using parent/guardian reports of sleep, Asian children slept an average of 23 min less than White children, while Latinx and Black children slept an average of 14 and 17 min less, respectively [10]. Despite these differences, there were no racial/ethnic differences in whether children were sleeping the recommended 9–11 hours per night for this age group [11].

Even universal sleep interventions focused on delaying school start times for the academic, physical and mental health benefits of adolescents suggest the importance of considering possible ethnic/racial differences. For example, a recent study of two Seattle public high schools found that a 55-min delay in school start time was associated with an average 34-min increase in actigraphy-recorded sleep duration [12•]. The school start time delay was also associated with higher grades and lower levels of daytime sleepiness overall; however, a reduction in absences and first-period tardiness was only observed for the school with a majority of ethnic/racial minority students (2% White versus 76% White). As such, it seems that delaying school start times may have a particularly meaningful impact on ethnic/racial minorities and may hold potential for addressing disparities.

To unpack ethnic/racial disparities in sleep across development, researchers have looked at both sociodemographic influences such as socioeconomic status and gender, environmental correlates such as residential crowding and substandard housing conditions, as well as behavioral correlates such as media use, physical activity levels, and having a regular bedtime [13–15]. Even statistically adjusting for these ‘usual suspects’, ethnic/racial disparities in sleep remain [16]. New research has begun to implicate ethnicity-/race-related stress to account for sleep disparities [17]. Specifically, ethnic/racial discrimination, and the stress associated with discrimination, has been observed to explain at least some of the ethnic/racial disparities in sleep [17,18••,19]. For example, a study of first-year college students found that Black students reported shorter sleep duration, as well as steeper increases in sleep disruptions over a one-year period compared to White students; however, ethnic/racial discrimination fully accounted for differences between Black and White students [18••]. Finally, in a study of Asian and Latinx adolescents, Asian students slept less than their Latinx peers; moreover, discrimination was associated with poorer, self-reported sleep quality for both groups [21]. Further underscoring the connection between discrimination and sleep disturbances, a recent systematic review of research investigating the link between discrimination and sleep found a consistent negative association (i.e. discrimination was associated with more sleep disturbance) across all 17 studies that were included in the review [22•].

In particular, three recent articles focused on sleep and discrimination among ethnic/racial minority adolescents shed light on the daily processes that might connect discrimination to sleep [23••,25•]. Using a combination of wrist actigraphy and daily diary surveys where adolescents completed daily reports of their discrimination experiences, researchers observed increases in sleep disturbance on the same days adolescents report being the target of discrimination [23••,25•]. In other words, the data suggest that experiencing discrimination on any given day is associated with compromised sleep the same night [23••,24••]. Collecting daily reports of discrimination experiences along with daily actigraphy reports provides unique and real-time insight into how discrimination stress is related to subsequent objectively assessed sleep disturbances. Over time, focusing on daily, cumulative processes has the potential to elucidate how sleep and health disparities might develop. Moreover, the mechanisms by which discrimination disrupts sleep, such as the role of rumination, loneliness and perceived stress have been suggested in previous studies [26,27], and examining these daily processes will extend the current science. Future studies will also benefit from moving beyond the cultural context of the United States, as well as considering the role of acculturation among immigrants [28,29].

Ethnic/racial differences in mental health

Sleep is not the only area where disparities are evident. Ethnic/racial minority groups contend with health disparities throughout the lifespan [30]. Mental health disparities demonstrate slightly different patterns than those of physical health. Compared to Black and Latinx groups, White adults reported higher levels of life satisfaction and lower levels of depressive symptoms [31]. Ethnic/racial minority groups including Black (i.e. African American, Caribbean), Latinx (i.e. Puerto Rican, Cuban, Mexican) and Asian adults (i.e. Chinese, Filipino, Vietnamese) also evidence higher levels of risk for mental health disorder (i.e. higher lifetime and annual prevalence rates) compared to their White counterparts [32]. In a population-based national sample, Black and Latinx adults had higher rates of major depression compared to Whites [33]. Schizophrenia and posttraumatic stress disorder are also more prevalent among Blacks and American Indians [34].

Beyond disparities in prevalence rates, there is also evidence of higher levels of severity and symptoms among ethnic/racial minorities relative to Whites [15,18••]. Mental health conditions appear to be more persistent and more severe among Blacks and Latinx patients [35]. Similar to sleep disparities, scholars have attempted to uncover sociocultural and contextual conditions and mechanisms related to mental health disparities, such as discrimination experiences [36], socioeconomic status, residential segregation, medical care [37], providers’ bias and stereotyping, ‘statistical discrimination’ (defined as actions that reflect group characteristics based on negative and exaggerated stereotypic beliefs), geographic differences, and health insurance disparities [35].

Linking ethnic/racial differences in sleep and mental health

Indeed, there may be reasons to connect disparities in sleep with disparities in mental health. Sleep has been well known to impact mental health [38,39], and mental health has also been observed to impact sleep [40]. As such, the disparities in sleep and mental health cited above are likely reciprocally associated [24••]. However, the dearth of research collectively examining sleep and mental health disparities has precluded more in depth understanding of these relationships. Even so, research is beginning to link disparities in sleep with disparities in mental health. For example, both daily actigraphy and self-reported sleep have been linked to compromised mental health among ethnic/racial minority adolescents and adults [25•,41,42]. Sleep duration has been found to be associated with self-esteem and positive mood, and negatively related to negative mood, anxiety, externalizing behaviors and depressive symptoms. Indicators of sleep quality, such as difficulty falling asleep (i.e. sleep onset latency) as well as sleep disturbance (i.e. night-time awakenings) have been found to be negatively associated with self-esteem, and positively associated with negative mood, anxiety, externalizing behaviors and depressive symptoms [25•,41,42]. In a study of Mexican-origin adolescents, discrimination was associated with subsequent internalizing symptoms as mediated through daily sleep disturbances [20•].

While more longitudinal studies are necessary to unravel the reciprocal associations between sleep and mental health, research exploring the links between sleep and mental health over time is limited, and research focusing on ethnic/racial minorities is even rarer. It is necessary to continue to gather longitudinal data with the intent of unpacking the reciprocal associations between sleep and mental health. For example, research focused on the college transition has found that depressive symptoms during the senior year of high school predict poorer sleep quality in the first year of college. At the same time, sleep difficulty before college predicts anxiety during the transition [43]. However, similar research including ethnic/racial minorities is essentially non-existent, as such, it is unclear how these data patterns might replicate or differ across ethnic/racial groups.

Research will benefit from future examinations of the explanatory pathways between sleep and mental health disparities. For example, in a study of ethnic/racial minority adolescents, better quality and longer actigraphy-recorded sleep duration the previous night was associated with better discrimination coping the next day [44•]. Specifically, previous night sleep was associated with more problem-solving and peer-support seeking coping and less rumination, which in turn resulted in better mental health the next day [44•]. Future research should consider exposure to trauma, adverse neighborhood conditions, differences in physical inactivity, vasomotor symptoms, positive affect and depressive symptoms, as potential pathways, or third variable influences, connecting disparities in sleep and mental health [45–47].

Conclusions

Researchers have uncovered ethnic/racial disparities in sleep and mental health that parallel disparities in physical health. Increasingly, the science suggests that it is also important to consider ethnic/racial discrimination as a possible third variable linking these two areas of disparities. Taken together, the state of the science suggests that research investigating sleep and mental health, and associated disparities, should take seriously the ethnicity/race of its participants. Doing so will begin to address how ethnicity/race are implicated in physical and mental health disparities more broadly. In particular, there is promising emerging evidence to explore ethnic/racial discrimination as a contributing, and possibly explanatory, factor in unpacking disparities in sleep and health.