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Creators/Authors contains: "Scullin, Michael K."

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  1. Free, publicly-accessible full text available December 1, 2025
  2. Free, publicly-accessible full text available August 28, 2025
  3. Free, publicly-accessible full text available June 1, 2025
  4. We investigated the factors that predispose or precipitate greater intra-individual variability (IIV) in sleep. We further examined the potential consequences of IIV to overall sleep quality and health outcomes, including whether these relationships were found in both self-reported and actigraphy-measured sleep IIV. In Study 1, 699 US adults completed a Sleep Intra-Individual Variability questionnaire and self-reported psychosocial, sleep quality, and health outcomes. In Study 2, 100 university students wore actigraphy and completed psychosocial, sleep, and health surveys at multiple timepoints. In cross-sectional analyses that controlled for mean sleep duration, predisposing/precipitating factors to greater IIV were being an under-represented racial/ethnic minority, having greater stress or trait vulnerability to stress, and showing poorer time management. In addition, both studies showed that greater sleep IIV was associated with decreased overall sleep quality, independent of mean sleep duration. Concordance across subjective and objective IIV measures was modest and similar to concordance observed for subjective-objective mean sleep duration measures. Risk for irregular sleep patterns is increased in specific demographic groups and may be precipitated by, or contribute to, higher stress and time management inefficiencies. Irregular sleep may lead to poor sleep quality and adverse health outcomes, independent of mean sleep duration, underscoring the importance of addressing sleep consistency. 
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  5. Many students self-report that they are “night owls,” which can result from neurodevelopmental delays in the circadian timing system. However, whether an individual considers themselves to be an evening-type versus a morning-type (self-reported chronotype) may also be influenced by academic demands (e.g. class start times, course load) and behavioral habits (e.g. bedtime social media use, late caffeine consumption, daytime napping). If so, then chronotype should be malleable. We surveyed 858 undergraduate students enrolled in demanding science courses at up to three time points. The survey assessed morning/evening chronotype, global sleep quality, academics, and behavioral habits. Evening and morning-type students showed similar demographics, stress levels, and academic demands. At baseline measurements, relative to morning-types, evening-types showed significantly worse sleep quality and duration as well as 22% greater bedtime social media usage, 27% greater daytime napping duration, and 46% greater likelihood of consuming caffeine after 5pm. These behavioral habits partially mediated the effects of selfreported chronotype on sleep quality/duration, even after controlling for demographic factors. Interestingly, 54 students reported switching from being at least moderate evening-types at baseline to being at least moderate morning-types later in the semester and 56 students showed the reverse pattern (6.3% of students switched from “definitely” one chronotype to the other chronotype). Evening-to-morning “chrono-switchers” consumed less caffeine after 5pm and showed significantly better sleep quantity/quality at the later timepoint. Thus, some students may consider themselves to be night owls in part because they consume caffeine later, take more daytime naps, or use more social media at bedtime. Experimental work is needed to determine whether nudging night owls to behave like morning larks results in better sleep health or academic achievement. 
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  6. Beginning in early 2020, the novel coronavirus was the subject of frequent and sustained news coverage. Building on prior literature on the stress-inducing effects of consuming news during a large-scale crisis, we used network analysis to investigate the association between coronavirus disease 2019 (COVID-19) news consumption, COVID-19-related psychological stress, worries about oneself and one’s loved ones getting COVID-19, and sleep quality. Data were collected in March 2020 from 586 adults (45.2% female; 72.9% White) recruited via Amazon Mechanical Turk in the U.S. Participants completed online surveys assessing attitudes and behaviors related to COVID-19 and a questionnaire assessing seven domains of sleep quality. Networks were constructed using partial regularized correlation matrices. As hypothesized, COVID-19 news consumption was positively associated with COVID-19-related psychological stress and concerns about one’s loved ones getting COVID-19. However, there were very few associations between COVID-19 news consumption and sleep quality indices, and gender did not moderate any of the observed relationships. This study replicates and extends previous findings that COVID-19-news consumption is linked with psychological stress related to the pandemic, but even under such conditions, sleep quality can be spared due to the pandemic allowing for flexibility in morning work/school schedules. 
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  7. Abstract Study ObjectiveWe investigated sleep disparities and academic achievement in college. MethodsParticipants were 6,002 first-year college students attending a midsize private university in the southern United States [62.0% female, 18.8% first-generation, 37.4% Black, Indigenous, or People of Color (BIPOC) students]. During the first 3–5 weeks of college, students reported their typical weekday sleep duration, which we classified as short sleep (<7 hours), normal sleep (7–9 hours), or long sleep (>9 hours). ResultsThe odds for short sleep were significantly greater in BIPOC students (95% CI: 1.34–1.66) and female students (95% CI: 1.09–1.35), and the odds for long sleep were greater in BIPOC students (95% CI: 1.38–3.08) and first-generation students (95% CI: 1.04–2.53). In adjusted models, financial burden, employment, stress, STEM academic major, student athlete status, and younger age explained unique variance in sleep duration, fully mediating disparities for females and first-generation students (but only partially mediating disparities for BIPOC students). Short and long sleep predicted worse GPA across students’ first year in college, even after controlling for high school academic index, demographics, and psychosocial variables. ConclusionsHigher education should address sleep health early in college to help remove barriers to success and reduce disparities. 
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