We’ve all experienced the effects of a bad night’s sleep: we’re tired, can’t concentrate and are generally unpleasant to be around. But why?
There’s nothing puzzling about it: science can explain why a sleep deficit affects our body and mood.
For starters, deep sleep is an important part of the way we release tension. Our sleep is divided into two states that work together in a cycle, quiet sleep (NREM) and deep active sleep (REM), which both need to run through their cycles before waking in order to replenish the body and brain, a process which takes seven to nine hours.
Light sleepers – those who are REM-deprived – and people who don’t sleep enough are prone to be more tense than people who get enough deep sleep. For example, employees who work the nightshift and sleep during the day don’t sleep as deeply, and as a result show more signs of stress.
In addition, sleep reduces our negative emotions. One study showed that, of the 31 participants who were struggling through a divorce, 20 worked through their emotions in their sleep. In their dreams, they dealt with their anger and sadness, playing through scenes with their ex-spouses and slowly improving their “dream reactions,” helping them to develop strategies to move on.
We take strong, unresolved emotions with us into our sleep, where our minds continue to work through them and help us to come to terms with them. For example, when we get upset by a nasty comment someone makes about our looks or weight, those emotions feel less powerful after a proper night’s sleep.
Finally, our endocrine system functions best when we get enough sleep because it affects the hormones that control our appetite. In fact, most people who sleep fewer than six hours a night will experience an increase in appetite, and studies have even shown that you’re 7.5 times more likely to be obese if you’re a short sleeper.