How sleep affects our mental health
Most of us have personal experiences of feeling grumpy and irritable after a night of poor sleep and living in a fast-paced society like Singapore, sleeping problems are common. A recent article by Lee et al., 2022 reported that 27.6% of people surveyed in Singapore reported having poor sleep quality.
While the nature and function of sleep remain largely unknown (Kanda et al., 2016), it is widely acknowledged that sleep is inextricably linked with the brain and that the brain does not function well without sleep. Many studies have demonstrated that poor sleep patterns or sleep disturbances have been associated with public health problems, such as cognitive impairments, increased dementia risk, neurological problems, and increased cardiometabolic risk (Baglioni et al., 2011; E. Lee et al., 2019; Low et al., 2019; Smagula et al., 2022). Furthermore, a systematic review on insomnia (Pigeon et al., 2017; Scott et al., 2021) found that there is a relationship between sleep quality and the development of mental illnesses, such as anxiety, bipolar disorder, depression and increased suicide risk.
How sleep disturbances can affect mental illness
The largest amount of evidence is strongest for depression, where many studies have found that sleeping difficulties double the risk of developing depression (Kang et al., 2016; Kuo-Hsuan et al., 2022; Ritter et al., 2015). Poor sleep quality is now considered a possible predictor of depression, rather than just a symptom. This correlation may have strong clinical implications, since early identification and treatment of insomnia may prevent the onset of depression (Baglioni et al., 2011).
Similarly, insomnia is a criterion for anxiety or anxiety-related disorders, such as post-traumatic stress disorder (PTSD) and generalized anxiety disorder (GAD). A possible explanation is that when sleeping difficulties are first developed, those at risk for developing specific anxiety disorders are vulnerable to excessive worry, not just about sleep. This will contribute to impaired executive functioning, leading to a reduced ability to cope and filter negative emotions. Evidence also supports a relationship between sleep quality and bipolar disorders /suicide risks. While not all neural pathways in insomnia were established, studies suggest that there may be a number of shared neuro- or psychobiological pathways where the occurrence of insomnia will lead to vulnerability in developing mental illness (Pigeon et al., 2017).
Thus, insufficient sleep or poor-quality sleep will not only affect your physical health but will also lead to mental health conditions, such as anxiety or depression. There is also a cyclic effect - if you have a pre-existing mental illness, it can be challenging to get good quality sleep; this will lead to poor sleeping conditions, which in turn, will exacerbate mental health disorders.
But what if we can’t sleep?
Circadian clock genes are required to control the body’s daily clock function of wakefulness and sleepiness (Lamont et al., 2007). While light is the main synchronizer to the circadian timing system, other factors such as food intake and physical exercise are also known to affect circadian rhythms (de Souza Teixeira et al., 2020; Rácz et al., 2018). While more randomized controlled trials are needed to establish a strong correlation linking clock genes with mental health disorders, some people with misalignment between their circadian phases and the sleep-wake cycle may be vulnerable to issues in mental health.
Sleep enables the process of emotional memories known as sleep-dependent memory processing, where we consolidate learning and contextualize fear or painful memories (Walker & Stickgold, 2004; Walker & van der Helm, 2009). Poor sleeping conditions hinder this ability to commit new experiences to memory, and ‘unlearn’ negative memories, potentially solidifying negative emotional memories.
While some of the sleep circuits underlying REM sleep generation have been identified, it is still a challenge for clinicians to identify other distributed neural circuits and understand the functional importance of REM sleep (Blumberg et al., 2020; Peever & Fuller, 2017). Since REM sleep occurs later in the night, or last one-third of the night, insufficient sleep will lead to a reduction of REM sleep. This reduction has potentially been shown to deter learning and consolidate memories.
Understanding links between social media use, sleep and mental health
Recent interest, particularly in the last decade, has been on the impact of the use of mobile devices and social media on sleep quality and mental health. There is a significant association between social media use in the nighttime and sleeping difficulties. While there may be an association between excessive social media, sleeping problems and mental health problems, the link is not straightforward. Poor sleep quality may be a contributing factor between social media use and mental health, but the interplay or bidirectional association between these three variables is not conclusive (Alonzo et al., 2021). An association does not imply a possible causal effect, so more studies are needed. However, in general, taking a hiatus from social media may bring better sleep quality, and a positive effect on one’s general wellbeing (Graham et al., 2020).
Tips for better sleep
Now that we have a broad picture of how sleep can affect our mental health, what then can we do to get a good night’s sleep?
Firstly, get enough sleep. The CDC recommends that an adult receives at least 7 hours of sleep. Shorter sleep duration reduces the number of REM sleep phases.
Avoid substances like caffeine and alcohol before bedtime. This will also reduce REM sleep phases, leading to poor quality sleep.
Block out excess light and sounds to maintain undisrupted sleep throughout the night.
Ruminating about the events during the day, especially those raising negative emotions, will result in disturbed sleep. Find ways to wind down, such as meditation, listening to music or other relaxation techniques, that will calm you down before bedtime.
Develop regular sleep schedules and meal frequencies to maintain circadian timing systems.
Put away mobile devices and reduce social media use in the nighttime.
Conclusion
It is important to note that differences in the above studies, such as research methods, sample sizes, different follow-up periods, subjective measures etc, may have complicated the relationship between sleep and mental health. However, with increasing literature on sleep quantity and quality, together with increasing recognition of the significance of mental health during COVID-19, sleep is likely to become an important intervention to one’s overall physical and mental health.
References
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