We’ve all heard and probably used the ‘wrong side of the bed’ phrase at some point or another. After a sleepless night we tend to feel more irritable and grumpy, we might find our reactions are a little more turbulent, we might have difficulty concentrating, feel lacking in energy, and have less enthusiasm for things we would usually enjoy.

Sleep goes a long way to determining our mood and emotional health. Previously we were under the impression sleep problems were just a symptom of poor mental health, but we now recognise their bidirectional relationship, that is it goes both ways!

Poor mental health and moods can affect our ability to sleep as they can get in the way of reaching the desired state of relaxation needed to sleep. When we feel anxious or stressed as a result of day-to-day life, we feel more agitated, aroused and alert, keeping us awake. We might find our brain won’t switch off, our heart rate is faster or breathing feels quick and shallow, quite the opposite of what is needed for sleep. When we’re feeling sad or low, perhaps due to a drop in serotonin levels, our sleep can be interrupted as serotonin (the ‘calming’ hormone) is needed for the production of melatonin (the sleep hormone) that allows the body to begin to switch off.

This principle applies to more severe or diagnosed mental health conditions too, such as depression or anxiety disorders, but the effects might be felt more regularly and intensely. Those experiencing mental health problems often report problems with sleeping and it’s often hard to determine which came first.

Let’s look at the stages of sleep to understand how sleep supports good mental health and vice versa.

The sleep stages are important because they allow the brain and body to recuperate and develop. Our brain activity fluctuates in different brain regions throughout the night to allow for different processing functions. Typically physical health is supported by ‘deep sleep’, and emotional health by Rapid Eye Movement (REM) sleep.

The first few stages of sleep are non-REM when we experience:

  • Dropping body temperatures

  • Slowing heart and breathing rates 

  • Muscle relaxation

The ‘deep sleep’ stage is critical for restorative sleep, essentially getting the physical rest we need to recover and grow. The brain activity in this stage is reduced, the slow brain waves seem to rinse the brain of harmful waste products, known as neurotoxins, that could otherwise damage brain cells. This ‘cleaning’ process occurs when cerebrospinal fluid flows in and out the brain, restoring our physiological health - essentially slowed brain activity in deep sleep allows for the brain to be cleansed, and without it we may see a build-up of these toxins resulting in poor brain health.

Then we enter REM sleep. This stage is vital for our emotional health as it facilitates what we might consider an ‘overnight counselling session’. During REM sleep brain activity ramps up and is associated with more intense dreaming. Although the brain is active, the body certainly is not. We experience something called ‘atonia’ which is a temporary paralysis of the muscles (don’t panic), bar those responsible for breathing and the eyes, which is why we might see our partner or children’s eyes darting about while they dream.

This stage is essential for facilitating cognitive functions such as memory, learning and creativity. REM sleep allows the brain to evaluate and remember our thoughts and memories from the day, processing and keeping the good bits, and dismissing the bad. So a lack of REM sleep is especially harmful to the consolidation of positive emotional content. This is why sleep deprivation influences mood, emotional reactivity and is tied to mental health disorders and their severity.

Now understanding the relationship between sleep and mental health is multifaceted, though it makes for complex connections between the two, it does mean that treatments for both tend to go hand-in-hand. There is even some evidence that improving sleep by addressing the issues, will have a positive impact on mental health conditions, like anxiety and depression. And further, some studies say sleep improvements may even form part of preventative mental health strategies. As we know everyone is different, it’s safe to say the optimal treatments will depend on the individual, however, because these conditions majorly impact our quality of life it’s so important to seek and receive proper care.


  • In order to sleep, our bodies and brains must be allowed to slow down and relax, try to stay away from overstimulating entertainment right before bed!

  • We need sufficient deep and REM sleep to facilitate physiological brain health, and good functioning in order to maintain good mental health, and don’t forget this works both ways!

  • We might look to tackle sleep problems to create mental health prevention strategies, so if we’re looking to improve our wellbeing why not start with sleep!

Beingwell have partnered with Welldoing to offer Welldoing visitors an exclusive offer on their products, including their Kip Advisor, an interactive sleep guide. Find out more and sign up for your free trial here.

Further reading

Can hypnotherapy improve your sleep?

Why mental energy is your most valuable asset

How CBT can help you overcome insomnia

10 ways to beat insomnia