You thought not getting enough sleep only really depleted your energy, and maybe put you in a bit of a bad mood. In fact, a flurry of recent studies have found sleep deprivation can affect you in a whole host of ways.
Here are six of the latest things to watch out for.
1. Your appetite goes haywire
You've probably noticed that if you're tired you get the munchies, and two new studies have explained why.
First, a team at the University of Chicago found that insufficient sleep raises levels of a molecule called 2-AG in the body that stimulates appetite. On top of that, the second study found that when you're sleep deprived parts of your brain that control food choices behave differently.
Activity in areas that help you make good decisions is blunted, while areas that give a feeling of reward from food ramp up their activity.
Defeat the damage: "Forewarned is forearmed," says Kate Swann, psychologist and author of Do You Really Want to Lose Weight?. "Try and spot the eating patterns you fall into when you're tired and beat them.
If, for example, you know you reach for sugar at 3pm, have a healthy snack at 2.30pm instead. Also, address your reasoning. Yes, you're tired and need a pick-me-up – but does it have to be food? Could you get a boost from a walk around the block instead?"
2. It interferes with your skin
"Our study is the first to conclusively demonstrate that inadequate sleep is correlated with reduced skin health and accelerated ageing," says Dr Elma Baron from University Hospitals Case Medical Center in the US.
In fact, she found that the skin of poor sleepers not only had more signs of ageing, it also didn't recover as quickly from damage from UV light and lost moisture faster than normal.
It's not known exactly why this occurs, but skincare company Estée Lauder (which funded Dr Baron's research) explains that the skin performs a purification process at night called catabolism which helps with skin repair. If sleep is disrupted this process doesn't happen as effectively.
Defeat the damage: Be extra vigilant with your SPF but also increase your consumption of foods like pomegranate, garlic and green tea – they have all been shown to protect against UV damage from within.
3. You’re more likely to fight with your partner
Even just one night of poor sleep can lead to arguments between loved ones – and those rows are likely to be more fierce than normal, say researchers at the University of California, Berkeley. They found that tiredness impairs your ability to gauge emotions, making it more likely someone will take offence for no reason.
Defeat the damage: Try not to argue when you're tired. But if an argument does start, relationship psychologist John Aiken suggests you avoid phrases that start with 'you always' or 'you never', as these often cause rows to blow up and spiral.
"It can also be tempting to slip into personal attacks, for example, 'you're lazy' or 'you're selfish', but don't. Keep focusing only on what you can do to resolve the situation and remain calm."
4. It changes how you look
The more tired you are, the more it shows on your face. Dr Tina Sundelin from Sweden's Stockholm University found that fatigued people looked paler, had more pronounced wrinkles and the corners of their mouth drooped down.
Not only does this sap confidence, it might even influence how well others treat you. "Studies on health perception are rudimentary but suggest people might want to avoid interaction with those who don't look healthy," she says.
Defeat the damage: Increase your fruit and vegetable intake by at least two portions a day. According to research from Scotland's University of St Andrews, doing so gives your skin a noticeably healthier glow in just six weeks – and it's believed higher doses may get even faster results.
5. Your brain gets cluttered
It's recently been discovered that during sleep your brain gets a detox. As you doze brain cells shrink in size by 60 per cent, creating space between them through which the body can detox harmful products like beta-amyloid, a substance linked to the development of Alzheimer's disease.
The less you sleep the less time the brain has to 'cleanse' – studies at John Hopkins Bloomberg School of Public Health in the US recently found that short sleep duration was linked to a greater level of beta-amyloid build-up in the brain.
Defeat the damage: "Last year we showed that the Mediterranean diet, rich in fruit, vegetables and fish, low in saturated fat and moderate in alcohol, correlates with reduced beta-amyloid build-up in the brain," says Professor Ralph Martins from Edith Cowan University in WA.
"The curry spice curcumin and pomegranate juice also inhibit build-up – but possibly the best medicine to reduce beta-amyloid levels in the brain is exercise." Even if you're tired try and get out for a brisk walk.
6. You worry more
Researchers at the University of California, Berkeley have discovered that when we're tired the part of our brain that amplifies worry and anxiety is more active.
The effect is so pronounced that the doctors behind the trial say people with anxiety disorders who don't sleep well should be having sleep therapy as part of their treatment.
Defeat the damage: "To stop worry taking over on tired days, create a worry period," says Sydney-based psychologist Amrit Grewal. "This is a set period of time in the day when you will tackle your worries. When worries occur, simply tell your brain you'll address them at this time and let them pass.
When you do get to the worry period, first ask if your 'what if' thoughts are realistic. Are they likely to eventuate and how bad, realistically, will they be if they do?
Most often you'll realise you're worrying about things that may never happen. If you don't though, turn your focus to action. Are there any concrete plans you can put into place to remedy the situation?"
New ways to sleep better
Obviously the best way to tackle all of these issues is to try and get more sleep – and science is hoping to help there too. Here are four new ideas…
People who get more natural daylight throughout their day – even through glass – sleep better at night, say researchers at Northwestern University in Chicago.
Do nothing: British sleep specialist Dr Guy Meadows' approach to poor sleep is revolutionary – using techniques like mindfulness, he teaches people how to do nothing to get to sleep! "It's what good sleepers already do – and what you did before insomnia took hold," he says.
Don't smoke: Yes, there's another reason to quit. New research has found smoking interferes with the production of proteins that control your body clock. Quitting can help normalise your sleep patterns.
Placebo sleep: Don't focus on how much sleep you missed, instead focus on the time you did sleep and tell your brain that you got enough to feel okay. When researchers at Colorado College in the US did this in a trial, people immediately performed better on tests of memory and information processing.