Sleep debt and depression in female college students

Abstract

The objective of the study was to evaluate relationships between sleep habits and depressive symptoms. Pilot study data were collected about sleep schedules, related factors and depression in female college students to find whether their sleep schedules correlate with affective symptoms. In the subsequent main study, similar information was collected under more controlled conditions. Depression was measured using the CES-D (Center for Epidemiologic Studies Depression Scale) and HAM-D-3 (modified Hamilton Depression Rating Scale). Response rates were 31.3% of eligible students for the pilot survey and 71.6% for the main study. Both studies showed that about 20% of students reported weekday sleep debts of greater than 2 h and about 28% reported significantly greater sleep debt and had significantly higher depression scores (P < 0.0001) than other students. Melancholic symptoms indicated by high CES-D scores (> 24), were observed in 24% of students. Sleep problems explained 13% of the variance for both the CESD scale and the HAM-D-3 scale. Among female college students, those who report a sleep debt of at least 2 h or significant daytime sleepiness have a higher risk of reporting melancholic symptoms than others.

Introduction

Many college students get irregular or insufficient sleep because of changes in life style and work schedules. College students report 2 to 5 times the number of sleep problems (McGhie and Russell, 1962, Raybin and Detre, 1969, Karacan et al., 1976, Lack, 1986). They go to bed at later, less predictable hours, arise later and less refreshed, and sleep fewer hours than their forebears did around 1910 (Webb and Agnew, 1975, Moo-Estrella et al., 2005). Between 1969 and 1989, their median daily sleep time fell by 1 h (Hicks and Pellegrini, 1991). More recently they report much daytime sleepiness and the use of hypnotic drugs (Raybin and Detre, 1969, Lack, 1986, Hicks and Pellegrini, 1991, American, 2005).

Poor nighttime sleep risks daytime sleepiness (Manber et al., 1996, Pilcher and Walters, 1997, Wolfson and Carskadon, 1998). Among subjects who averaged 7 h of sleep a night, self-reported sleep quality explained daytime sleepiness better than sleep quantity did (Pilcher and Walters, 1997). Adolescents 13 to 19 years old with short school-night sleep and/or long delay in bedtime on weekends were more likely to experience daytime sleepiness (Wolfson and Carskadon, 1998).

Chronic sleepiness probably risks depressive symptoms (Wolfson and Carskadon, 1998, Hublin et al., 1996, Feng et al., 2005, Carney et al., 2006). People who self-report habitually short or insufficient nighttime sleep as well as clinical patients who sleep late show unexpectedly high rates of depressed mood (Carney et al., 2006, Regestein and Monk, 1995). Epidemiological surveys confirm that finding (Breslau et al., 1996). Conversely, earlier bedtime and arising time may be associated with better sleep quality. Relatively more variable sleep may be associated with poor daytime functioning (Moo-Estrella et al., 2005), while “regularization of sleep-wake schedules” reportedly reduced sleepiness (Manber et al., 1996).

Sleep varies so widely among individuals that researchers often find weak correlations among subjective sleep, objective sleep, disordered sleep, and cognitive functioning (Sugerman et al., 1985, Edinger et al., 2000, Ohayon and Roth, 2001, Regestein et al., 2004, Klerman and Dijk, 2005). The complex nature of sleep impedes using any single, standard measures to define sleep (Edinger and Means, 2005). Researchers routinely use subjective sleep measures (Lack, 1986; Weitzman et al., 1981), since decrements in subjective sleep tend to be validated by adverse physical and mental daytime consequences (Sugerman et al., 1985, Edinger et al., 2000, Ohayon and Roth, 2001, Regestein et al., 2004).

The term “depression” is ambiguous, because standard questionnaires combine items related to melancholic or mood-related symptoms with items related to appetite, somatic symptoms or fatigue. To our knowledge, correlations between quantitative measures of sleep and specific types of depressive symptoms have not been reported in college students.

Here, we report a study that tested whether diminished or delayed sleep correlated with specific types of depressive symptoms. We hypothesized that diminished sleep quality would correlate with increased fatigue-related depressive symptoms. To provide fuller information and better understanding of relationship between sleep and common daytime symptoms, we also report pilot results from a broader student sample, as well as correlations found among sleep-related habits.