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