How Psychological Stress Affects Sleep: A Literature Review

How Psychological Stress Affects Sleep: A Literature Review
Jessica C. Henschel and Austin Mardon

This research paper will examine the effects of psychological stress on sleep disturbances and some of the treatments available today. The focus of this paper is psychological stress, not the physiological aspects of chronic or acute stress; psychological stress can be defined as any uncomfortable emotional experience that is accompanied by behavioural changes, feelings of worry, or being overwhelmed (American Psychological Association [APA], 2017). Based on the literature, psychological stress has been linked to sleep disorders such as sleep deprivation (insomnia), hypersomnia, and less frequently, more serious conditions like sleep apnea; these disorders are detrimental to an individual’s mental and physical health, along with their social, academic, and occupational lives. Stress can be found in many areas of life, and there are many types of acute and episodic psychological stress that people face, such as academic, social, situational, and emotional stress. While acute stress is not always negative, chronic stress is a major problem for many people, as it causes an unrelenting state of pressure and mental arousal (APA, 2017). All these different kinds of stress affect a person’s sleep cycle differently
Sleep is crucial for the body to function properly, as it affects both mental and physical health. This time of rest is when the brain is able to repair and build new pathways, thus preparing the body for the next day. It is also when the body repairs the heart and blood vessels, along with multiple other crucial physical functions (National Heart, Lung, and Blood Institute, 2012). Sleep deprivation is the most detrimental to health, as it can produce serious consequences such as decreased performance and alertness, memory and cognitive impairment, increased risk of accidents (occupational and automobile accidents), obesity, and in some cases, even temporary psychotic-like behaviours (Breus, 2006).
In order to assess the relationship between stress and sleep, I began by looking at various articles that performed empirical studies on the basic link between episodic stress — as well as chronic — and sleep problems. In essence, is there a causal, correlational, or no link between the variables? DeSilva Mousseau et al. (2016), examined the relationship between sleep duration and stress in female adolescents. The participants were 218 female students from varying socioeconomic and cultural backgrounds that attended two different same-sex secondary schools. In order to determine a link between perceived stress and sleep, DeSilva Mousseau et al. (2016) ran Ordinary Least Squares (OLS) regression models (cross-sectional and longitudinal), along with a Perceived Stress Scale (PSS) where the participants were asked to rate their level of stress. The students were also asked to subjectively rate how they believed their stress affected their sleep quality and duration. It was found that in both of the tests performed, there was a potential reciprocal relationship between stress and sleep; stress was significantly negatively associated with sleep, such that an increase in stress was predictive of a decrease in sleep duration. 
In the cross-sectional analysis, the data showed that higher levels of stress produced fewer hours of sleep and vice versa. The longitudinal test produced similar results with more insight on the negative, lingering effects of stress and poor sleep. 88% of the girls in Test 1 and 91% of the girls in Test 2 were getting less than eight hours of sleep a night even during non-exam times; which can be attributed to the suggested lingering effects of sleep found in the longitudinal results. With the given limitations of only examining females in a specific age range, it is hard to avoid a Type 1 error of lack of generalization. Based on the limitations and the nature of the research design, this evidence was deemed correlational; however, this is still valuable information to the topic as it established empirical evidence that moves us closer to discovering the link between stress and sleep.
Another empirical study was performed to determine a link between both chronic and acute occupational stress and sleep quality. Pow et al. (2017) looked at the effects of psychological, occupational stress on sleep. Eighty-seven paramedics were asked to fill out a diary upon waking and then again when they got home from work. The participants were required to journal about how well they felt they slept and their perceived amount of work-related stress. The conditions were based on the paramedic’s off-work days, dayshifts, and nightshifts. After one week of this method, the results were analyzed using multilevel modelling that measured occupational stress, sleep quality, and perceived social support.
Pow et al. (2017) found a correlational link between stress and sleep; the more perceived occupational stress an individual had, the lower sleep quality was reported. Based on their secondary research hypothesis about social support, they found that social support buffers sleep from the potentially harmful effects of stress. Conclusively, this study was limited due to the sample consisting of only paramedics and did not look at any other workers employed in stressful occupations. It was also a very short study that concluded few results. Overall, this research was evidence to support that there may be a correlational link between psychological stress and sleep quality. Furthermore, this research suggests that emotional and social support may be beneficial for people dealing with stressful work lives, thus helping them to achieve proper sleep patterns.

 Occupational psychological stress was also examined by Pereira et al. (2016). Their study looked at two main areas: how social stress at work affects sleep quality, and how the quality of sleep can help mediate recovery time from those stressors. In order to measure this, forty-one participants wore actigraphs and filled out a diary to record sleep duration for two nights (from Saturday to Monday). Sleep actigraphy was used to measure sleep duration and awakenings during the night with the use of small watch-like devices.
Social stress was measured by self-report questionnaires. The surveys were designed to assess working conditions, general demographic information, and were followed by social stress at the work scale. This was used to examine interpersonal tension or issues with colleagues or supervisors at the individual’s place of work. Recovery also needed to be measured in order to determine if sleep does in fact help recovery times for work-related stressors. Recovery status was measured on a scale of 1-7 (1-exceedingly bad to 7-exceedingly good) and was interpreted on how fatigued the individual felt and if they felt as though they had recovered from their acute occupational stressors (Pereira et al., 2016).
By running various linear regression analyses, Pereira et al. (2016) found that increased social stressors at work were correlated with decreased recovery time due to poor sleep quality and duration. The higher stress ratings were associated with more awakenings during the night, which was measured by the actigraph. The number of times individuals were awake/restless was more frequent on Sunday nights which may be related to the psychological stress and mental unrest of going back to work on Monday. These results strengthen the assumption that acute stress at work can lead to an incomplete recovery period.
Similarly, Phuong Uy and Galván (2017) looked at how insufficient sleep patterns are correlated to enhanced levels of stress (acute) and poor decision-making under those stressors. By using a daily diary approach with the combination of physiological tests, they were able to collect data from both adolescents and adults on their sleep duration. Twenty-two adolescents between the ages of 15 and 17, and twenty-two adults between the ages of 25 and 30 participated in the study. To measure sleep duration, participants were asked to fill out a self-report questionnaire about how much sleep they had in the past month. Stress was rated using Ecological Momentary Assessment (Phuong Uy & Galván, 2017) which consisted of each individual rating their daily, subjective stress level on a smartphone. By using a Likert scale from 1-7 (1= not stressed and 7= very stressed), the participants were able to easily report their stress levels three times a day, allowing Phuong Uy and Galván (2017) to collect average daily stress indications.

Phuong Uy and Galván’s (2017) findings suggest that sleep deprivation amplifies the effect of daily psychological stress and risky decision-making behaviors under stress. Based on the results, it appears that longer sleep hours may work as a protective force against stress, and may even allow an individual to adapt to stressful situations and make more benefit-cost analyses in risky situations, even when faced with stressors.  However, the limitations of this study were evident in the use of the self-report scales for sleep duration. Even with this drawback, this article also shows a correlational relationship between stress and sleep, whilst adding onto the already known research with the addition of decision-making and how individuals handle stress with either an increase or decrease of sleep.
Based on the current research into stress and sleep, there is no causal evidence that stress does in fact cause sleep disorders or disturbances. As stated in the literature review above, there is strong correlational evidence between episodic, acute, and chronic stress and many types of sleep disorders, especially insomnia and sleep deprivation. Further research needs to be done to look at how stress can affect serious sleep disorders such as sleep apnea or narcolepsy. There has been very little research that looks at how psychological stress is linked to physiological sleep disorders. It would be interesting to see more research on how psychological stress can affect the different stages of sleep such as REM and NREM, and how this changes the physiological functions of sleep. In conclusion, this area is still growing, and in order to help those who suffer from psychological stress and sleep disorders, more research needs to be done. 

References
American Psychological Association. (2017). Understanding chronic stress.      http://www.apa.org/helpcenter/understanding-chronic-stress.aspx
Breus, M.J. (2006, March 15). Sleep Habits: More Important Than You Think. http://www.webmd.com/sleep-disorders/features/important-sleep-habits#2 
DeSilva Mousseau, A.M., Lund, T.J., Liang, B., Spencer, R., & Walsh, J. (2016). Stressed and losing sleep: Sleep duration and perceived stress among affluent adolescent females.         Peabody Journal of Education, 91(5), 628-644. http://dx.doi.org/10.1080/0161956X    2016.1227186
National Heart, Lung, and Blood Institute. (2012, February 22). Why is sleep important?      https://www.nhlbi.nih.gov/health/health-topics/topics/sdd/why
Pereira, D., Gross, S., Elfering A. (2016). Social stressors at work, sleep, and recovery. Applied   Psychophysiology and Biofeedback, 41(1), 93-101. http://dx.doi.org/ 10.1007/s10484-     015-9317-6
Phuong Uy, J. & Galván, A. (2017). Sleep duration moderates the association between insula     activation and risky decisions under stress in adolescents and adults. Neuropsychologia, 95, 119-129. http://dx.doi.org/10.1016/j.neuropsychologia.2016.12.018
Pow, J., King, D.B., Stephenson, E., & DeLongis, A. (2017). Does social support buffer the        effects of occupational stress on sleep quality among paramedics: A daily diary study.        Journal of Occupational Health Psychology, 22(1), 71-85.             http://dx.doi.org/10.1037/a0040107