The Importance of Sleep

We all appreciate the importance of sleep, and feel the impact when we don’t get enough of it. But why is it so important, and what are the impacts on our body and mind if we don’t get what we need?

What is sleep?

Our circadian rhythm is an internal mechanism that operates on roughly a 24-hour cycle, which determines functions such sleeping, eating, urination, hormone secretion, body temperature, and mood. Our circadian rhythm keeps our internal functions in phase with the outside world. Typically, the human circadian clock generates a rhythm slightly longer than 24 hours when it has no external cues to it; external – or environmental – cues that synchronise our biological rhythms to the Earth's 24-hour light/dark and 12-month cycle include light most dominantly, but also exercise, arousal, meals, and environmental temperature.

Sleep occurs according to our circadian rhythm, but also according to other factors such as age, body mass index, psychological factors such as stress, anxiety, and depression, environmental factors such as room temperature, television or device use, and family or social commitments (Nelson et al., 2022).

Sleep consists of 5 different stages, which occur in cycles, each cycle being around 90 minutes long:

• Non-REM (nREM) sleep includes stages 1-4:

  Stage 1 sleep. Sleep has just begun, and our cortex continues to have high amounts of input.

Stage 2 sleep. Activity in this stage tends to increase after new learning.

Stages 3 & 4 are together called slow wave sleep. During these stages input from the cortex is greatly reduced. These two stages predominate earlier in the night.

• REM (Rapid Eye Movement) sleep. During this stage, there is increased neural activity; our muscles are very relaxed and heart rate, blood pressure, and breathing rate are more variable, and facial twitches and eye movements occur. More cycles of REM occur toward the end of the night. Dreaming occurs in both REM and nREM sleep, but it is understood to occur more often and more vividly in REM sleep.

What are the consequences of poor sleep? 

Sleep quality is defined as an individual's self-satisfaction with all aspects of the sleep experience, which includes sleep efficiency, sleep latency, sleep duration, and wakefulness after sleep onset (Nelson et al., 2022). Sleep deprivation is the experience of insufficient sleep to support the body’s adequate functioning.

Research conducted on conditions of poor sleep quality or in states of sleep deprivation occur either in controlled study environments, or in real-life settings using participants who experience reduced sleep due to long working hours or shift work (e.g., physicians and nurses).

Studies have shown that event short-term sleep deprivation can result in or is associated with:

• Physical consequences, including:

  Increased vulnerability to physical illnesses (Hanson & Huecker, 2022; Nelson et al., 2022)

  Impaired post-physical activity recovery (Troynikov et al., 2018)

  Increased incidence of accidents and injuries (Elliman et al., 2020; Hanson & Huecker, 2022)

• Mental and emotional consequences, such as:

  Higher rates of mental health disorders (Freeman et al., 2017; Hanson & Huecker, 2022; Nelson et al., 2022; Torquati et al., 2019)

  Impaired mood (Hanson & Huecker, 2022; Troynikov et al., 2018)

  Increased emotional reactivity (Tempesta et al., 2017)

  Significant increases in anxiety levels, with larger increases observed in greater periods of sleep deprivation (Pires et al., 2016)

  Psychotic experiences (Freeman et al., 2017)

• Cognitive consequences, including:

  Impaired cognitive performance generally (Kecklund & Axelsson 2016; Troynikov et al., 2018)

  Impaired task performance (Troynikov et al., 2018)

  Increased vulnerability to false memory retrieval (Lo et al., 2016)

  Impaired emotional memory encoding and retrieval (Tempesta et al., 2017)

Poor sleep quality even over the short term has been shown to result in or is associated with:

• Impaired decision-making (Troynikov et al., 2018)

• Impaired speed and accuracy of task performance (Troynikov et al., 2018)

• Impaired post-exercise recovery (Troynikov et al., 2018).

Chronic sleep deprivation has shown to be associated with increased low-grade systemic inflammation and impaired hypothalamic-pituitary adrenal (HPA) axis functioning (a neuroendocrine system regulating many bodily processes, and our body’s reaction to stress). Chronic sleep deprivation has been associated with greater impulsivity, slower cognitive processing, and impaired executive function in workers (Choshen-Hillel et al., 2021).

A recent review of the literature demonstrates the significance of sleep deprivation, suggesting that a worker or driver should be deemed reasonably impaired if they obtained less than 5 hours of sleep in the preceding 24 hours (Dawson et al., 2021). Of particular concern is our inability to subjectively assess impairment following poor sleep, even over the very short-term. Research has shown that we tend to perceive that our performance is either unaltered or less impacted following poor sleep than objective measures of task performance indicate (Ganesan et al., 2019). In other words, we think we perform better under conditions of poor sleep than what we actually do. So, if you think you will perform at your normal level of functioning following a late night out, you’re likely to be wrong!

Improving your sleep

A meta-analytic study suggested that improving sleep leads to significant improvements in mental health, depression, anxiety, rumination, stress, and some psychosis symptoms. Greater improvements in sleep quality led to greater improvements in mental health (Scott et al., 2021).

Influenceable actors such as caffeine intake, use of devices in bed, daytime napping, and timing of exercise and eating can influence sleep quality. Recommendations around adjusting such practices to optimise sleep are referred to as sleep hygiene practices. Further information about sleep hygiene recommendations can be found here.

At the commencement of therapy I will generally ask about a number of lifestyle factors, including your sleep. If sleep difficulties are evident, I may suggest that we additionally set some goals around your sleep hygiene practices. Even minor changes can lead to improvements in your sleep, which can result in improvements in your ability to regulate your mood and engage in many of the practices that we may discuss in therapy.

Specific psychological treatments exist for sleep disorders, such as insomnia. Please contact me if you are seeking treatment for a sleep disorder specifically, to check our suitability in working together.