Elsevier

Sleep Medicine

Volume 15, Issue 1, January 2014, Pages 144-149
Sleep Medicine

Original Article
Sleep and sadness: exploring the relation among sleep, cognitive control, and depressive symptoms in young adults

https://doi.org/10.1016/j.sleep.2013.10.006Get rights and content

Highlights

  • Poorer self-reported sleep quality predicted increases in depressive symptoms.

  • Sleep quality and stability predicted poorer cognitive control over negative stimuli.

  • Poor cognitive control was associated with increases in depressive symptoms.

  • A path diagram integrated the above findings into a single statistical model.

  • A polymorphism in the CLOCK gene was associated with self-reported sleep difficulty.

Abstract

Background

Sleep disturbance is a common feature of depression. However, recent work has found that individuals who are vulnerable to depression report poorer sleep quality compared to their low-risk counterparts, suggesting that sleep disturbance may precede depression. In addition, both sleep disturbance and depression are related to deficits in cognitive control processes. Thus we examined if poor sleep quality predicts subsequent increases in depressive symptoms and if levels of cognitive control mediated this relation.

Methods

Thirty-five undergraduate students participated in two experimental sessions separated by 3 weeks. Participants wore an actigraph watch between sessions, which provided an objective measure of sleep patterns. We assessed self-reported sleep quality and depressive symptoms at both sessions. Last, individuals completed an exogenous cuing task, which measured ability to disengage attention from neutral and negative stimuli during the second session.

Results

Using path analyses, we found that both greater self-reported sleep difficulty and more objective sleep stability measures significantly predicted greater difficulty disengaging attention (i.e., less cognitive control) from negative stimuli. Less cognitive control over negative stimuli in turn predicted increased depression symptoms at the second session. Exploratory associations among the circadian locomotor output cycles kaput gene, CLOCK, single nucleotide polymorphism (SNP), rs11932595, as well as sleep assessments and depressive symptoms also are presented.

Conclusions

These preliminary results suggest that sleep disruptions may contribute to increases in depressive symptoms via their impact on cognitive control. Further, variation in the CLOCK gene may be associated with sleep quality.

Introduction

Sleep disturbance is a common feature of depression and as such represents one of nine symptoms of a depressive episode [1]. Some estimates suggest that up to 90% of individuals with major depression also are diagnosed with insomnia [2]. There also is empirical evidence that depression is associated with nonclinical sleep disturbances (e.g., reduced total sleep time, increased sleep-onset latency) [3]. Importantly, recent research shows that sleep disturbance may not only be a symptom of depression but may in fact precede the disorder. For example, Chen et al. [4] found that daughters of depressed mothers reported poorer sleep quality than girls at low familial risk for depression. In addition, sleep restriction has been shown to increase depressive symptoms among otherwise healthy individuals [5]. In sum, sleep difficulties characterize depressive episodes and may serve as a phenotype of risk for the disorder. Therefore, our study sought to identify the underlying mechanisms by which sleep difficulties may contribute to depression symptomatology.

It is possible that sleep disturbance influences depressive symptoms through its impact on cognition. Indeed, sleep difficulties and depression have been independently linked to deficits in cognitive control. For example, sleep deficits are associated with poor performance on tasks measuring mental flexibility [6], working memory [7], attentional set shifting [8], and inhibition [9]. Depression also has been linked to cognitive control deficits, particularly during emotional information processing. Depressed individuals exhibit difficulties inhibiting the processing of negative material [10], [11], disengaging attention from negative material [12] and removing negative material from working memory [13]. Given these results, our study examined if sleep difficulties are associated with reduced cognitive control over emotional stimuli and if these reductions are linked to increases in depressive symptoms.

Notably, much of the work on sleep and depression has relied on self-report measures. However, it is possible that negative reporting biases which often precede and characterize the disorder may account for observed group differences. Therefore, any study of sleep and depressive symptoms should consider including both self-report and objective measures of sleep disturbance. Actigraphy represents one method to objectively examine sleep in a naturalistic setting [14]. Actigraph devices use an accelerometer to measure movement across time and researchers can use movement data to infer periods of sleep and wakefulness. In contrast to other sleep methodologies (e.g., sleep deprivation, polysomnography [PSG]), actigraphy allows researchers to objectively measure naturalistic sleep outside the laboratory. In addition to measuring traditional sleep measures such as total sleep time, actigraphy also can provide measures of circadian rhythms [15]. Especially in the cognition literature, there is evidence that circadian rhythm measures account for outcomes above and beyond those accounted for by average sleep duration or changes in sleep duration [16], [17], [18]. Additionally, although some individuals have conceptualized depression as a disorder of disrupted circadian rhythms [19], research on the relation between sleep–wake cycles and depression is lacking. Therefore, our study utilized both subjective and objective measures of sleep difficulties and circadian rhythms to examine their relation to cognitive control and depressive symptoms.

Our study recruited a sample of undergraduate students to identify factors that may underlie the relation between sleep difficulties and depressive symptoms. In doing so, we first examined the relation between sleep and depressive symptoms. In line with previous findings, we hypothesized that poorer sleep quality and reduced sleep duration would predict increases in depressive symptoms. Second, because previous research has linked both sleep and depression to deficits in cognitive control, we hypothesized that cognitive control over negative stimuli would mediate the relation between sleep quality and change in depressive symptoms. As a final exploratory objective of the study, we explored if variation in a single nucleotide polymorphism (SNP) in the circadian locomotor output cycles kaput gene, CLOCK, related to our primary variables of interest (i.e., sleep, cognitive control, depressive symptoms). The CLOCK SNP, rs11932595, was chosen because it has previously been linked to variation in daily sleep time [20].

Section snippets

Participants

Researchers posted flyers at The University of Texas at Austin advertising a study on sleep and cognition. Current undergraduate students at The University of Texas at Austin who were at least 18 years of age were eligible to participate in the study. Individuals who responded to the flyers via e-mail received a written description of the study. Individuals who remained interested in the study and who met inclusion criteria were scheduled for the first laboratory session.

Fifty-two individuals

Descriptive statistics

Means, SDs, and correlations among the relevant variables are presented in Table 1. We first examined the relation between sleep and depressive symptoms. Depressive symptoms and self-reported sleep difficulties were moderately correlated. Total sleep was moderately associated with depression symptoms at time two but fell short of statistical significance (P = .08). Sleep stability (IS), fragmentation (IV), and variability (SD) were weakly associated with depressive symptoms at both time points.

Discussion

Our study explored the relation among sleep, cognitive control, and depressive symptoms in a two-session study with a sample of undergraduate students. First, we found that self-reported sleep quality between the two laboratory sessions predicted depressive symptoms at time 2 after controlling for depressive symptoms at time 1. Specifically, poorer sleep quality was associated with greater increases in depressive symptoms. This finding supports those of Chen et al. [4], suggesting that sleep

Conflict of interest

The ICMJE Uniform Disclosure Form for Potential Conflicts of Interest associated with this article can be viewed by clicking on the following link: http://dx.doi.org/10.1016/j.sleep.2013.10.006.

. ICMJE Form for Disclosure of Potential Conflicts of Interest form.

Acknowledgments

The authors would like to thank the Chief of the Army—Grant to West Point Network Science Center, subcontracted to The University of Texas at Austin, for funding this study.

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