Why were we interested in this research?
It is well known that sleep disturbances such as insomnia affect people with both anxiety disorders (panic disorder and generalised anxiety disorder) and bipolar disorders eg bipolar 1, and bipolar 2.
Also, according to the DSM-5 (The Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition), the internationally recognised manual for assessing and diagnosing mental disorders, sleep disturbances are a key diagnostic criterion in both bipolar and anxiety disorders.
One aspect of mental health research involves identifying factors which can negatively impact an individual’s quality of life. By identifying these factors, it is possible to develop methods to effectively manage and/ or treat an individual’s mental condition.
One of these factors is called comorbidity.
Comorbidity is where the individual experiences more than one mental health or medical condition at one time (Valderas et al., 2009). Comorbidity can significantly worsen a person’s illness prognosis, access to treatment, and receipt of accurate diagnoses (Piccirillo & Costas, 2004).
Studies have found that around 51% of people with bipolar disorder – at one point in their lives – will experience some form of anxiety disorder.
Given the high rate of comorbidity between bipolar and anxiety disorders, as well as the fact that both of these conditions are susceptible to experiencing sleep-related disturbances, it is surprising that there has been little research looking at this issue to date.
The aim of our study was to identify whether people with bipolar disorder and comorbid anxiety were more likely to experience greater sleep disturbances compared to people with bipolar disorder alone.
What did we do?
A total of 101 volunteers were recruited through the NCMH. These volunteers were asked to complete a questionnaire on their typical sleeping patterns over the course of a month, in addition to wearing an activity/sleep monitor (also known as Actigraphy) for a six-week period.
You may be thinking, why did we use two measures of sleep quality rather than just one?
This allowed us to examine the differences and/or similarities between our volunteers’ sleep behaviours (e.g. time spent asleep/ awake), and their perceptions of their own sleep (i.e. what they believed their sleep was like).
What did we find?
Overall, our findings surprised us.
Whilst we expected to find that people with bipolar disorder and comorbid anxiety would demonstrate greater sleep disturbances on both the sleep questionnaire and actigraphy measures, this was not the case.
Instead, people with bipolar and comorbid anxiety perceived their sleep to be poorer than those with bipolar alone. Also, our volunteers with and without comorbid anxiety did not differ on actigraphy measures. Indicating that comorbid anxiety did not affect peoples’ actual sleep.
What could explain these findings?
Whilst we cannot definitively say if the presence of anxiety causes people to experience sleep disturbances, our findings do help us understand what may be contributing to the perception of sleep disturbances experienced by those with bipolar disorder.
One explanation of our findings might be so-called Sleep Misperception.
Sleep misperception is where people experience a great deal of worry, alertness, and anxiety before sleeping.
This causes the individual to perceive their sleep as being poor; however, this cannot be detected by behavioural sleep measures such as actigraphy (Harvey & Tang, 2012).
Another explanation of our findings could be that the tools we used, i.e. actigraphy, were not able to detect sleep disturbances in these volunteers.
Research has shown that sleep behaviour measures, such as actigraphy, are not always sensitive enough to detect certain aspects of sleep. These include the very short periods in which we awake in the night or how much time we spend in deep sleep (Sadeh, 2011; Harvey & Tang, 2012).
We need to conduct further research to establish whether people with bipolar disorder and comorbid anxiety experience poorer sleep, or whether this is due to another factor we are yet to discover!
What are the future implications of our research?
As this study is the first of its kind, there is a large scope for further research.
To address the drawbacks of our study, future research could use more accurate measures of sleep behaviours and brain activity such as Electroencephalography (EEG).
EEG is a method of measuring brain activity using sensors attached to a person’s scalp. Electrical signals in certain areas of the brain indicate activity and allow us to assess a person’s sleep (e.g. different sleep stages).
In spite of this, our research highlights the importance of treating sleep and anxiety symptoms in people with bipolar disorder.
Potential benefits of improving sleep in people with bipolar disorder include increased quality of life, reduced risk of relapse, and better overall physical and mental health for those experiencing bipolar disorder (Harvey et al., 2009).
In the future, we hope that we can follow on from these findings and develop a better understanding of the relationship between comorbid anxiety and sleep disturbances in people with bipolar disorder.
We would like to thank all of the NCMH volunteers for kindly giving their time to take part in this research.
Read the full article
Resources
- Bipolar disorder
- Anxiety and panic attacks
- Bipolar Education Programme Cymru (BEPC)
- NCMH mental health leaflets | Sleep problems and how to manage them
- NCMH Podcast | Sleep, insomnia and mental health
- Sleep Foundation | Mental Health
- NHS Every mind matters | Sleep and mental health
Read more
- Understanding sleep problems
- Five factors that could be affecting your sleep
- NCMH Research Champion blog | Bipolar and sleep – Chasing the Zeds