A recent study published in Cognition and Emotion has brought to light how fragmented sleep is associated with a reduced ability to control our emotions. Specifically, one night of fragmented sleep led study participants to fixate their thoughts on negative ideas, and this was significantly associated with stronger negative feelings the next day.
Fragmented sleep results from brief awakenings during the night, leading to poor sleep quality. Such disrupted sleep not only leaves individuals feeling tired the following morning, but also often leads to a decline in positive mood and an increase in negative mood. But the exact mechanism on why sleep impacts our emotions is not well established.
One theory is that sleep modifies our emotion regulation abilities. Emotion regulation involves using our thoughts and actions to control the emotions we feel and how these emotions are expressed. These can be divided into adaptive and maladaptive strategies.
Adaptive emotion regulation strategies aim to be helpful in boosting our mood – for example, viewing a situation in a more positive manner (’cognitive reappraisal’), accepting emotions as they are and not feeling a desire to change these emotions (‘acceptance’), and focusing attention to something more neutral or positive (’distraction’).
In contrast, maladaptive strategies are often harmful and sours our mood – for example, not outwardly expressing emotions (’suppression’), constantly thinking about a situation negatively (’rumination’), and judging oneself negatively (’self-criticism’).
Merel Elise Boon and colleagues from Radboud University in the Netherlands set out to investigate the impact of sleep fragmentation on these six emotion regulation strategies, and consequently how mood was impacted.
Sixty-three female and six male Radboud University students aged 18 to 29 were recruited for the study, which ran over 12 consecutive nights. The participants wore an Actiwatch on their wrist each night, which is a device that objectively tracks sleep through movement, in addition to filling out a sleep diary each morning, which provided subjective details about their sleep.
On day six, participants either slept normally for one night (the control night), or experienced sleep fragmentation whereby they were woken up by an alarm every 80 minutes.
Entering the morning of day seven, the participants completed the emotion regulation task. This task firstly consisted of viewing a neutral film clip from a nature documentary to put all the participants in a similar emotional state. Following this, a sad film clip was shown as a baseline measurement. Finally, the participants were provided instructions to use one the emotion regulation strategies of cognitive reappraisal, distraction, acceptance, or suppression, before being shown a different sad film clip.
After the task on day seven, participants filled out surveys which measured how much they used cognitive reappraisal, distraction, acceptance, suppression, rumination, and self-criticism, as well as their current positive and negative emotions.
This process was repeated the following week, but instead the participants were in the opposite condition. For instance, if they received normal sleep previously they then experienced sleep fragmentation, and vice versa.
Upon analysis of the data, the researchers found that participants reported lower levels of positive emotions following sleep fragmentation compared to sleeping normally, however, the level of negative emotions did not differ.
Most notably, participants reported increased rumination following sleep fragmentation. Out of all the emotional regulation strategies investigated, only rumination was found to be associated with stronger negative emotions the morning following sleep fragmentation. The researchers suggest that this may be due to poor sleep quality disrupting the ability to control attention, therefore disrupting the ability to remove attention away from negative thoughts. On a longer time-scale, “the mood impairing effects of rumination following poor sleep… could lead to the onset of [depression],” Boon and colleagues propose.
Participants also self-reported more distraction following sleep fragmentation. Boon and colleagues hypothesized that the participants used distraction more often as a counteractive adaptive strategy due to having more maladaptive ruminative thoughts after sleep fragmentation. Interestingly however, distraction was found to reduce positive emotions, so the researchers suggest further investigations are required.
Finally, there was no evidence that any of the emotion regulation strategies played a role in the relationship between sleep fragmentation and positive emotions.
The researchers highlighted a few limitations of their study. For instance, the sleep stage the participants were woken up from was unclear. Previous research has demonstrated links between disrupted deep sleep and poor emotion regulation, so if participants were woken up during light sleep, this may have led to less of an impact upon emotion regulation abilities.
Furthermore, males and females have been found to differ in their main choice of emotion regulation strategies. Thus the results cannot be applied to a broader population as the majority of participants were female.
Despite some shortcomings of the study, this study effectively investigates the short-term effects of poor quality sleep upon mood, and opens up questions for further scientific research, such as the consequences of long-term poor sleep quality.
The study, “The effect of fragmented sleep on emotion regulation ability and usage“, was authored by Merel Elise Boon, M.L.M. van Hooff, J.M. Vink and S.A.E. Geurts.