In this series, we publish blog posts written by our undergraduate students for the PB101 Foundations of Psychological Science course. In this post, Ami Byrne examines the complex interplay between sleep and affective states, exploring how sleep quality and emotional well-being influence each other and discussing the broader implications for mental health and daily functioning.

Sleep is at the core of being human, as we spend ‘up to one-third of our lives sleeping or attempting to do so’ (Aminoff et al., 2011). It is valuable, therefore, to investigate the effect of sleep on other aspects of life. This blog will explore the relationship between sleep and emotions. By “emotion” we mean how we respond physiologically to an external stimulus, through chemical reactions in the nervous system controlled by neurotransmitters such as dopamine, serotonin and adrenaline, and how we behave as a result, together with our underlying subjective experience of this whole process.

In this blog we’ll investigate this relationship, while also examining the limitations of historical studies and available data. The key questions posed are: to what extent do characteristics of sleep (e.g. duration and quality) have a bidirectional relationship with emotion and emotional regulation? Do they exist in a reciprocal causality, meaning they do not just affect, but cause each other? Or, is there a third variable that connects them, meaning the relationship is correlational, but not necessarily co-causative? This research is important as an increased understanding of sleep and mood, and subsequently related disorders, can decrease the burden on healthcare services. Also, by maximising sleep and positive affect, we can increase human productivity and ultimately, derive an economic benefit.

By maximising sleep and positive affect, we can increase human productivity and ultimately, derive an economic benefit.

When looking at emotions, two key aspects of our subjective experience are emotional regulation (ability to exert control over one’s affective state), together with the valence of our emotional response (either positive or negative). In terms of sleep, key variables are duration and quality, which can be measured both in terms of self-report, but also in terms of sleep-onset latency (the amount of time between going to bed and falling asleep). Ratio of Rapid Eye Movement (REM) to slow wave or ‘deep’ sleep is also an important predictive factor, since slow wave sleep is considered to be the most restorative form of sleep, with research suggesting it is critical for growth and recovery of both mind and body, linking it to positive emotional regulatory processes. The ratio of deep sleep to REM is an indicator of quality of sleep, as a higher ratio suggests an increase in these restorative processes; however, it should be mentioned that REM is undoubtedly valuable for learning and memory (Peever & Fuller, 2015).

Research suggests a two-way relationship between emotional regulation and sleep, such as Amada-Boccara et al’s study of women self-reporting their sleep and regulation over a two-week period. It concluded that both positive and negative emotions correlate with sleep. Positive affective states were predictive of high deep sleep ratio and sleep-onset latency, and sleep quality was similarly predictive of greater happiness, over subsequent days. Such research supports the idea of a bi-directional relationship between these two processes. However, since a mutual relationship is all that has been exhibited, this research is limited in its inability to infer causality. The use of self-report is heavily unreliable, as it relies on introspection, a data collection technique heavily flawed in its subjective bias and need for honesty. Therefore, this isn’t sufficient to allow us to conclude definitively that sleep and emotions are co-causal, merely that each is heavily correlated with the other.

Further studies show that sleep deprivation limits our ability to regulate stressful emotions from day to day (Baum et al., 2014). Baum et al performed a 3-week sleep manipulation protocol on 50 teenagers involving a baseline week, a 6.5 hour a night ‘sleep restriction’ condition, and a 10 hours a night ‘healthy’ sleep condition. Sleep was monitored via self-report and actigraphy (a non-invasive measurement tool, worn like a wristband). The participants self-reported as significantly more tense/anxious and angry/ hostile during sleep restriction conditions. The study concluded that sleep restriction causes more negative emotions, but that this is because sleep deprivation limits one’s ability to regulate negative emotions. In other words, regardless of whether people are in worse moods as a result of sleep deprivation, they will be more sensitive to any negative emotions that occur and may self-report more significant findings. This research has greater validity than the study above, as the experimental design was counterbalanced and randomised. This conclusion accords with the general scientific belief that ‘sleep impairment corresponds to affective dysfunction’ (Yoo et al., 2007), although it provides no information as to the inverse relationship. It may be, then, that sleep affects our ability to manage our emotional state, but more data is needed to say the opposite is true.

In terms of investigating the impact of emotions on sleep, the concept that poor emotional regulation of negative affective states impairs sleep certainly has face validity, as sleep is closely associated with wellbeing. It has been suggested that high positive affect can be associated with increased sleep onset latency and duration (Kalambach et al., 2014), with ‘serenity’ being the most consistent predictor of increased sleep quality in a self-report method approach over a 2-week period. This certainly suggests a link between subjective perception of mood and sleep. Furthermore, Akerstedt et al’s 2002 study found a direct link between stress and social situations at work and sleep quality, which serves as support for the effect of emotion on sleep. The relevance of the stress response is important here, as it directly relates to the physiological component of the emotional response. The adrenaline and cortisol released in response to a perceived stressor causes physiological changes in the body, which further disrupts sleep. This may explain how certain negative affective states cause sleep disruption, through regulatory processes that fall under the category of ‘emotional responses’.

So what can we conclude, in terms of the relationship between emotions and sleep? Existing research seems to support a bi-directional relationship, but it is harder to prove co-causation beyond any doubt. Research is limited, partially due to a lack of available data, but also due to validity issues. Measuring emotional response is a heavily subjective process, creating issues in terms of the introspection method mentioned above, as well as due to intervening variables such as social desirability (e.g. where people want to present themselves as having good wellbeing and high positive affect to researchers). We all have the experience of feeling cranky after a bad night’s sleep, or being unable to sleep when assailed by stress the night before. But it may be that there are other variables, such as personal history or psychological resilience, which have just as significant an impact on how we respond to sleep deprivation or negative emotions. In today’s increasingly fast-paced and stressful world, however, the balance of the data still points to the importance of regulating our emotions and getting a good night’s sleep.

• This post was originally written as part of PB101: Foundations of Psychological Science, which is a core course on the BSc Psychological and Behavioural Science. It has been published with the permission of the author.
• The opinions in this post are of the author, not of the Department of Psychological and Behavioural Science or LSE.
• Cover image by Ron Lach from Pexels.

References

• Akerstedt T., Knutsson A., Westerholm P., Theorell T., Alfredsson L. & Kecklund G. (2002) Sleep disturbances, work stress and work hours: a cross-sectional study. Journal of Psychosomatic Research 53(3). Link.
• Amado-Boccara I., & Donnet D., & Olié J.P. (1993) La notion d’humeur en psychologie [The concept of mood in psychology]. Encephale, 19(2), pp. 117-122. Link.
• Aminoff M.J., Boller F., & Swaab D.F. (2011). We spend about one-third of our life either sleeping or attempting to do so. Handbook of Clinical Neurology, 98:vii. Link.
• Baglioni C., Spiegelhalder K., Lombardo C., & Riemann D. (2010). Sleep and emotions: a focus on insomnia. Sleep Medicine Reviews, 14(4), pp. 227-238. Link.
• Baum K.T., Desai A., Field J., Miller L.E., Rausch J., & Beebe D.W. (2014). Sleep restriction worsens mood and emotion regulation in adolescents. Journal of child psychology and psychiatry, 55(2), pp. 180-90. Link.
• Goedert, K.M., Zhang, J.Y., & Barrett, A.M. (2015) Prism adaptation and spatial neglect: The need for dose-finding studies, Frontiers in Human Neuroscience, 30(9). Link.
• Hobson J.A., Pace-Schott E.F., & Stickgold R.  (2000). Dreaming and the brain: toward a cognitive neuroscience of conscious states. Behavioral and Brain Sciences, 23(6), pp. 793-842; discussion pp. 904-1121. Link.
• Kalmbach D.A., Pillai V., Roth T., & Drake C.L. (2014) The interplay between daily affect and sleep: a 2-week study of young women. Journal of Sleep Research., 23(6), pp. 636-645. Link.
• Peever, J., & Fuller, P.M. (2016) Neuroscience: A distributed neural network controls REM sleep, Current Biology, 26(1), pp. R34-5. Link.
• Triantafillou S., Saeb S., Lattie E.G., Mohr D.C., & Kording K.P. (2019). Relationship between sleep quality and mood: Ecological Momentary Assessment Study. JMIR Mental Health, 6(3). Link.
• Vandekerckhove M., & Wang Y.L. (2017). Emotion, emotion regulation and sleep: An intimate relationship. AIMS Neuroscience, 5(1), pp. 1-17. Link.
• Yoo, S.S., Hu, P., Gujar, N., Jolesz, F.A., & Walker, M.P. (2007). A deficit in the ability to form new human memories without sleep. Natural Neuroscience, 10, pp. 385–392 (2007). Link.