The relationship between sleep and mental health

The relationship between sleep and mental health is both complex and reciprocal. Interrupted sleep, poor quality sleep and difficulty falling asleep can all lead to mental health issues. Similarly, mental health difficulties can lead to sleep problems too. It’s a two-way street that implicates our hormones, and impacts our physical, emotional and mental health.

The importance of sleep for mind and body

Sleep is imperative for the normal functioning of our minds and our bodies. While we sleep, our brain gets to work unhindered by the external stimuli we encounter throughout the day. Sleep is the time our brain allocates for repairing and rejuvenating our bodies, boosting our immune system function, consolidating memories and processing our emotions.

During the earlier stages of ‘quiet sleep’ (before REM sleep) our body temperature drops, heart and breathing rates slow and muscles relax. Our brain takes this opportunity to direct the production of cytokines which are needed to help us fight infection and inflammation. This boosts our immune system and helps us remain physically healthy and able to fight off diseases and viruses.

As we cycle into REM sleep – the period when we dream – our body temperature, breathing, heart rate and blood pressure rise again to levels similar to that of when we are awake. Our amygdala and hippocampus surge into action, the parts of our brain that are partially responsible for processing emotions and motivation. The prefrontal cortex is notably inactive, taking a rest from logic, self-criticism and being the ‘voice of reason’; some experts think this may be the reason for the sometimes bizarre and illogical nature of our dreams.

Throughout both the quiet and REM cycles of sleep, which are repeated throughout the night for varied durations, our body produces a range of different hormones that act as messengers from the brain to parts of our body. These hormones are responsible for all manner of things – appetite, growth, healing, emotions and mood to name just a few. When sleep becomes disrupted and the quality of sleep doesn’t allow us to cycle through each of these stages for long enough, or as many times as is needed, our brain is unable to direct the right balance of hormone production that will allow us to function properly physically and mentally and maintain homeostasis.

How mental health impacts sleep (and vice versa)

Depression, Anxiety, ADHD and Bipolar disorders have all shown links with sleep disorders. More than 70 types of sleep disorders exist, but the most common are insomnia, obstructive sleep apnea, movement syndromes and narcolepsy.

Insomnia and other sleep disorders can increase the risk of depression, a mental illness experienced by roughly 6.7% of Americans. What’s more, those suffering depression are more likely to experience insomnia, making them less likely to respond to treatment. When treatment for the associated sleep disorder is given, improved outcomes for patients with depression are far more likely.

Anxiety is more common than any other mental illness in the United States, affecting around 40 million Americans each year. This mental illness can begin as a reaction to stress and is highly treatable. The heightened level of stress and anxiousness puts the body’s nervous system on alert, thus making it extremely difficult to rest and sleep. Both insomnia and hypersomnia (oversleeping) are common companions of anxiety disorders – as the person suffering may respond to the exhaustion of anxiety induced insomnia with bouts of hypersomnia.

ADHD or Attention Deficit and Hyperactivity Disorder impacts the lives of around eight to ten percent of school aged children and their families. ADHD symptoms and the medication used to treat this illness can both result in sleep difficulties. One study found that treating sleep disorders associated with ADHD eliminated symptoms of this mental illness entirely for some children.

The relationship between sleep, mental and physical health is a complex and involved one that is not yet entirely understood. What is understood however is the importance that sleep plays in creating a healthy lifestyle – too much or too little can result in poor mental health, physical illness and emotional difficulties.