What would happen if you stopped sleeping, day by day

• "Why do we sleep?" has been a notoriously difficult question for scientists to answer, but, "What happens if we don't?" is actually pretty simple — nothing good.
• Not getting enough sleep can make you hallucinate, mess with your thinking and memory, and even lead to organ failure.
• And it doesn't take very long at all for these negative effects to start occuring. As little as 18 hours, in fact.
• After 72 hours, your perception of reality could be all off. Here's what would happen to your brain and body, day by day, if you stopped sleeping.

Following is a transcript of the video.

Not getting enough sleep won't just make you cranky. It could kill you. The United Nations even considers sleep deprivation a form of torture. And the longer it lasts, the worse it'll get. Losing sleep affects people differently, but generally the effects increase as the hours do. Just 48 hours without sleep is considered extreme sleep deprivation, but you'll probably get weird before then.

After 18 hours with no sleep, you might feel a little drunk. Staying awake that long is equivalent to having a blood alcohol content of 0.05%, which is what you get with three or four drinks in the span of two hours.

24 sleepless hours, that BAC comparison jumps to 0.1%, higher than the legal driving limit in every state. You might feel foggy, less alert, or uncoordinated, almost like you're wearing sleepy beer goggles, including double or blurry vision. That's because sleep deprivation slows down our brain cells' ability to talk to each other. So if you actually are drinking alcohol, drowsiness can increase its effects. And while caffeine could make you feel more alert for several hours, it'll only work up to a certain point.

By a day and a half, this could all get worse and then some. Your chances of getting sick are higher than usual because your body can't fight like it normally can, and around this time, your brain and body get so tired that you start experiencing microsleeps, tiny periods of sleep, maybe around 30 seconds, that you might not even notice. Definitely annoying and even dangerous if you're doing something like driving a car. And then there's the potential for hallucinations. Visual distortions are most common. Your water bottle grows to twice its size or moves around the room. But you could also experience sensational or auditory hallucinations, things like feeling someone who's not there tap you on the shoulder or hearing your name being called. [ghostly voice whispering inaudibly]

Once you hit 48 hours, it's literal torture, which is why extreme-sleep-deprivation studies are now prohibited by law in most countries. Two days without sleep can cause you to start losing your grip on reality. Hallucinations worsen, and you might even undergo depersonalization. That's the feeling that reality is slipping away, which may or may not include an out-of-body experience. Tack on extreme anxiety, irritability, stress, and fatigue, and it's no wonder the UN doesn't allow this kind of deprivation.

After 72 hours, you're not gonna be able to think about anything but hitting the hay. Forget about doing simple tasks. Things like getting dressed or finding a snack could feel overwhelming, partially from fatigue and partially because your ability to regulate emotions is basically out the window. Your hallucinations could get more complex, creating fully formed images like a person, or a bear, or maybe a car you shouldn't drive. And in at least four historical sleep studies, participants reported shared hallucinations, namely something called the hat phenomenon, which is basically a feeling of pressure around your head as if you're wearing a hat. All of this opens the door for paranoia, depression, and delusions.

Which brings us to 96 hours or more with no sleep. Say bye-bye to reality, folks. More and worse hallucinations and paranoia could lead to sleep-deprivation psychosis, a total snap from the real world. Historically, women accused of being witches were kept awake long enough to trigger this psychosis. Judges considered their visions and ramblings confessions, leading to the women's convictions. Now, the fifth day is sometimes called the turning point. This is the danger zone. Your mental health takes a sharp decline, cementing your delusions as your new reality. Eventually, your brain will stop functioning properly in a way that could lead to organ failure and, in rare cases, death.

Luckily, recovering from sleep deprivation can be as simple as catching up on sleep, but if you're sleep deprived regularly, you're looking at long-term effects like weight gain, acne, headaches, and high blood pressure, among other things. And it can take weeks to get back on track. According to one study, you need four days to recover from losing a single hour of sleep. Try getting to bed early instead of sleeping in late, or, better yet, avoid the recovery period entirely by getting seven to eight hours of sleep every night in the first place.