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Dr Jo Bower, School of Psychology, answers questions on her research into the effects of the menstrual cycle on sleep and emotion.
Briefly, how does the menstrual cycle affect sleep?
Sleep changes are often found in the perimenstrual phase (i.e. in the days leading up to and during menstruation). Previous research has found that during this time, sleep quality declines and sleep disturbances increase. The reasons for this remain under-explored, but may include hormonal changes, such as a rise in progesterone which increases our core body temperature. However, much of the previous work has been done in older women, or those who experience severe pre-menstrual symptoms. Our study assessed healthy women aged 18 –35 and tracked their sleep and emotions over two full menstrual cycles. We found that during the peri-menstrual phase, women were awake for up to 15 minutes longer during the night and reported feeling sleepier in the daytime. They also had reduced sleep efficiency (i.e. the proportion of time spent in bed asleep was lower).
Psychologically, how does a lack of sleep affect us?
"We found that sleep loss was particularly detrimental for positive emotions, which show a large decline in response to lack of sleep."
Lack of sleep affects every aspect of our daytime psychological functioning, including our memory, attention, and our reaction times. However, it has the strongest effect on our mood and emotional responses. In our recent meta-analysis, we found that sleep loss was particularly detrimental for positive emotions, which show a large decline in response to lack of sleep. Conversely, negative emotions show smaller changes, but are still affected by lack of sleep. In the current study, lack of sleep interacted with menstrual phase, so that if women experienced poor sleep in the perimenstrual phase, they also experience a small reduction in positive emotions. This was interesting because positive emotions didn’t generally change for our participants across the menstrual cycle, except when sleep loss was present in the perimenstrual phase.
Why is it important that we understand the connection between the menstrual cycle and sleep?
"Women also experience higher levels of mood disorders such as depression, which may be connected to the menstrual cycle, both directly, through changes in hormones, and indirectly via changes in sleep."
Insomnia prevalence is higher in women, compared to men and the reasons for this remain unclear. However, these gender differences in prevalence only emerge following puberty, suggesting that the menstrual cycle may play a key role in perpetuating increased insomnia in women. Understanding the mechanisms which underpin this relationship is a crucial first step in identifying new interventions which may help women who experience insomnia and/or menstrual difficulties. Additionally, women also experience higher levels of mood disorders such as depression, which may be connected to the menstrual cycle, both directly, through changes in hormones, and indirectly via changes in sleep. Clarifying the relationship between the menstrual cycle and other aspects of health may lead to improved health benefits across of a range of domains for women.
How could this research be further developed to reduce vulnerability to mood disorders?
There are likely multiple direct and indirect associations between the menstrual cycle and vulnerability to mood disorders. However, we know that there is a strong association between sleep disruption and mood disorders, and that sleep problems often precede the onset of other mental health conditions. To explore these associations further, it would be interesting to replicate some of these findings experimentally – for example by assessing whether women are more vulnerable to sleep loss in specific menstrual phases by experimentally restricting sleep at different points in the menstrual cycle. It would also be useful to conduct longitudinal work, to track the changes in sleep and emotional health over time, in relation to the menstrual cycle. This may give us a clearer idea of how female hormonal changes map onto changes in sleep and emotional health.
Read ‘Interaction of sleep and emotion across the menstrual cycle’ in full in the Journal of Sleep Research, and "Sleep Loss and Emotion: A Systematic Review and Meta-Analysis of Over 50 Years of Experimental Research" in Psychological Bulletin.
Dr Jo Bower is interested in the interactions between sleep and emotional responding, and how these can influence our mental health and wellbeing. She is particularly interested in how these relationships change during adolescence and into adulthood, as adolescence is a period of significant neurobiological development, and is also a time when mental health problems often first emerge. Additionally, she is interested in factors that affect the sleep-emotion relationship, including the menstrual cycle, and how these relationships change during exposure to extreme environments.
