Emotions are an important part of being human. Recent studies on emotions have shown that along with shaping how we behave throughout the day, they also have a drastic effect on how we sleep. So this week, I thought examining the relationships between emotions and sleep would be good topic to cover.
Before I delve into the literature, there are two things I would like to briefly talk about. First, in psychology we love to talk about these things called “bidirectional relationships.” What this means is that two variables each have an effect on each other. In other words, emotions can affect sleep and sleep can also affect emotions.
Second, insomnia is a tricky topic. There is a lot of debate in the field whether it is a disorder on its own, or a symptom of another disorder. According to the International Classification of Sleep Disorders, you receive an official diagnosis if you have difficulty falling asleep and/or maintaining sleep throughout the night, there is no other presenting clinical disorder, and you also experience symptoms of daytime fatigue, decreased cognitive functioning, memory, attention, motivation, and irritability for at least four weeks. However, insomnia is also considered a symptom of several psychiatric disorders, such as depression. This perspective is well researched and it has been found that if you treat insomnia symptoms in individuals with major depression it not only improves their sleep, but also their other depressive symptoms.
Now, let’s take a look at the bidirectional relationships between emotions and sleep. Individuals who have insomnia symptoms for at least two weeks are at higher risk for developing depression in the following three years. Additionally, longitudinal studies have complimented the idea that poor sleep is a risk factor for the development of major depression.
Sleep deprivation studies have also shown that insufficient sleep time leads to poor mood regulation. In these studies, participants are brought into the lab overnight and are only allowed to sleep for four hours. Upon awakening, they are shown a series of different pictures that evoke emotions of anger, sadness, fear, and disgust. When compared to participants who were allowed to sleep an adequate amount of time, they reported higher ratings of anger, sadness, and fear. Other studies have even found differences in physiological responses. Measuring pupil dilation is a well-established test of emotional stimulation; the more emotionally stimulating, the larger the pupil dilates. In these studies, sleep deprived individuals had larger dilations when presented with negative stimuli than did the control group.
Looking at the other side of the relationship, different mood states can affect sleep. Loneliness is one of the more negative emotions that one can experience, and can be defined as the difference between one’s desired and actual relationships. The larger the discrepancy, the lonelier one may feel. One particular study examined how loneliness may affect sleep. Participants answered several questionnaires and were then divided into three groups: lonely, middling, or non-lonely. It was found that those in the “lonely” group had more restless sleep, and also spent more time awake throughout the night. Further research has added to this study, showing that sleep disturbances are positively associated with higher levels of self-reported loneliness. While these studies claim that loneliness may be causing poor sleep, there is something important to consider. Poor sleep leads to daytime fatigue, which can cause social withdrawal, which can then lead to loneliness. Much more research is needed in this area to establish this relationship.
Now let’s talk about romantic love. A recent study recruited participants and divided them into three groups: adolescents who reported recently falling in love, reported being in a long-term relationship, or reported being single and not in love. Those who were in “intense love” reported less daytime sleepiness, higher daily concentration, more physical activity, and better mood. However, they also reported significantly shorter sleep time. These participants were comparable to someone in a hypo-manic state! The researchers explained these findings in a fascinating way. While intense love may lead to a shorter quantity of sleep due to increases in arousal, it may actually improve the quality of your sleep. Much more research is needed, but these positive emotions may lead to more time spent in the deep stages of sleep.
So why is all of this important? Mood and sleep have a complex, yet important relationship. Depression and other negative mood states can have a detrimental effect on your quality of life, and decreasing your risk for these might be something as simple as making sure you attain adequate sleep every night.
Baglioni, C., Spiegelhalder, K., Lombardo, C., & Riemann, D. (2010). Sleep and emotions: A focus on insomnia. SleepMedicine Reviews, 14, 227-238.