Advertisement

healthHealth and Medicinehealthneuroscience
clockPUBLISHED

What Causes Motion Sickness, And Why Do Some People Get It More Than Others?

"Stay put" - evolution, 500 million years ago

author

Dr. Katie Spalding

author

Dr. Katie Spalding

Freelance Writer

Katie has a PhD in maths, specializing in the intersection of dynamical systems and number theory.

Freelance Writer

share36Shares
Person in a car, holding a white plastic bag, looking nauseous

Why does your body get pukey on the road?

Image Credit: Alona Siniehina/Shutterstock.com

Nothing ruins a road trip like the feeling of needing to vom all over your car mats – and yet, for more than one in four of us, it’s pretty common. Motion sickness is annoying for some, debilitating for others, and strikes seemingly at random, with some people getting it their entire lives and others never experiencing it at all. Still more may feel that tell-tale nausea in some circumstances but not others; at one time of their life but not another; heck, the feeling can even be worse depending on where you’re at in your menstrual cycle.

So what is behind this mysterious and unpredictable phenomenon? Why do some of us have to suffer it while others don’t? And, most importantly, what can we do about it when it strikes?

Advertisement

Who gets motion sickness?

If there’s one thing worse than getting motion sickness, it’s having it while traveling with someone who doesn’t. Here you are, trying every folk remedy you’ve heard of to try not to chuck in your friend’s mom’s car, while said friend is calmly reading a classic novel in the back while looking as comfortable as a long-haired cat that’s just found your favorite freshly laundered sweater.

“What gives?!” you might think – and the good news is, there are answers.

The bad news is, there aren’t many. “Motion sickness affects people differently, and there’s no single reason why some people experience motion sickness more frequently than others,” explained Saima Rajasingam, a lecturer in audiology at Anglia Ruskin University in a piece for The Conversation.

For instance, we know that “experiences peak around nine or ten years of age, and are more common in women,” she continued. “However, it is uncertain as to why this may be the case.”

Advertisement

For some of us, the urge to hurl on the highway may literally be in our DNA: there are a whopping 35 genetic variants associated with motion sickness, according to a 2015 study that analyzed data from 23andMe. Twin studies have corroborated the genetic angle, with one 2006 study estimating that as much as 57 percent of a person's susceptibility to motion sickness may be inherited.

Motion sickness can go hand-in-hand with other disorders – it seems to be tightly linked to migraine susceptibility, for some reason, while inner ear problems such as Ménière’s disease also increase the likelihood of experiencing motion sickness, Rajasingam noted.

For some of us, it may just be the roll of the dice. “Some people are just unlucky,” Timothy Hain, an otoneurologist and professor emeritus at Northwestern University, told The Atlantic back in 2015. “[They’re] wired to be more sensitive to motion than others.”

What causes motion sickness?

There are two suggestions as to what’s behind that familiar nausea – one you probably have heard before, and one you may not have.

Advertisement

The first, more common explanation is that it’s your body getting confused by a clash of sensory data. “As we move through space, multiple sensors in our middle ear, limbs and eyes feed information to our balance center in our brains to orientate us,” explained UNSW Sydney pharmacology professor Ric Day and University of Sydney Dean of Pharmacy Andrew McLachlan in The Conversation. “It’s when these sources of information are in apparent conflict that we may experience motion sickness.”

This theory essentially puts the blame for motion sickness on our balance system. Usually, our bodies keep us upright – or walking in a straight line, or simply able to pat ourselves on the head without missing – by harnessing a complex network of sensory input from our eyes, our muscles, and the sloshing around of the fluid in our inner ears. 

Imagine walking up a hill, for instance: our eyes see the vertical lines of the buildings around us; our muscles pick up on the increase in pressure on our feet and the unevenness in our weight as we take a step; and the fluid in our ears tells us that we’re currently upright, despite the funny angle at which we’re walking.

The problem comes when one of those inputs disagrees with the others. In a plane, for example, our eyes and muscles are convinced we’re sitting still, reading a book, or watching an in-flight movie – our inner ear, meanwhile, is very aware that we’re being pitched and yawed and rolled through the sky at approximately 600 miles per hour.

Advertisement

“This is also why the less sensory mismatch we experience in a vehicle, the less likely we are to experience motion sickness,” Rajasingam wrote. “For example, traveling in a car on a smooth, straight road will cause less sensory mismatch than traveling on a winding road with lots of potholes.”

Of course, there’s a slight problem with that explanation: we all have inner ears and eyeballs, and yet not all of us get motion sickness. But this is where the second explanation of the nauseating phenomenon comes in: perhaps, some argue, it has to do with our posture.

As anybody who has tried to take a long-exposure photo without stabilization knows, the human body is constantly moving. Even standing still requires muscle activation: “If you relax all your muscles, you collapse on the floor,” University of Minnesota kinesiologist Thomas Stoffregen told The Atlantic.

Precisely how we make all these little movements is unique to each of us – though it does follow some general rules. For example, “in women, the weight tends to be carried in the hips, and in men, in the chest,” Stoffregen said. “You have a big mechanical difference there.”

Advertisement

If the theory is correct, it’s enough to account for the discrepancy between the sexes, Stoffregen said. In experiments, "if you were going to get sick you swayed this way, if you weren’t, you swayed this other way,” he explained. Similarly, it explains why children are more susceptible than adults to yakking in the car: “Before puberty, boys’ and girls’ bodies are not all that different,” Stoffregen pointed out. “And after, they are.”

Why would this result in motion sickness? Once again, it comes down to a mismatch between what our bodies expect, and what they actually experience.

“Ships are an obvious example,” Stoffregen told Vox. As the vessel tips this way and that, our bodies’ usual micro-movements that should keep us upright are instead fighting against an unpredictable environment: “When the floor is rolling and pitching under you, there will be some body movement that is not under your control,” he said.

Of course, none of that explains why exactly our bodies think throwing up is the right thing to do – but there is one, admittedly controversial, explanation for that, too.

Advertisement

“The deeper, more fundamental subconscious systems that regulate our bodies don’t really know how to deal with such internal problems as this,” wrote neuroscientist Dean Burnett in his 2016 book The Idiot Brain. “In fact, as far as the reptile brain is concerned, there is only one likely answer: poison.”

“In nature, that is the only likely thing that can so deeply affect our inner workings and cause them to get so confused,” he explained. “Poison is bad, and if the brain thinks there is poison in the body, there is only one reasonable response: get rid of it, activate the vomiting reflex, pronto.”

How to cope with motion sickness

So, if we know – or, at least, suspect – the cause of motion sickness, surely we can treat it, right?

Well, to an extent, yes. If we take Stoffregen’s explanation as a starting point, for example, we can deduce a potential remedy: simply try to reduce the amount of uncontrolled movement your body experiences. Sit in the center of the plane, where the turbulence and movement are lowest; consciously anchor your head to the headrest in a car; wherever you are, try to sit in as stable a position as possible.

Advertisement

This may also be why certain medications such as Dramamine can reduce motion sickness, Stoffregen said. “Any sedative will tend to make you move less or wish to sit down as opposed to stand, lie down as opposed to sit,” he explained. “Anything that will stabilize the body will help.”

Similarly, any action we can take to reduce discordance within our balance system may help. “The longer the experience lasts and the larger the size of the movement, the worse the symptoms,” advised Rajasingam. “For example, traveling on a small boat in a storm for more than eight hours will cause quite severe symptoms – whereas a one-hour train journey will probably have little effect, even if the track isn’t perfectly smooth.”

Some treatments take a little of both. If you’re one of those people who feel sick in the passenger seat of a car, but not as a driver – which is a pretty common experience, it turns out, “probably because drivers are (unsurprisingly) much better at anticipating the motion of a vehicle and move their bodies according to the movement of the vehicle,” Rajasingam explained – then your best bet is to, essentially, pretend to be the driver: focus on the horizon, Hain suggests, and “do everything the driver does.”

And if all else fails, at least there’s this: eventually, motion sickness will almost certainly abate. Not just long-term, with age, but within a single journey. 

Advertisement

“There tends to be a reduction in symptoms after a couple of days at sea,” Day and McLachlan assure. “Medicines can then be reduced and even stopped.” 

“Symptoms often return when back on dry land, usually for just a day or two,” they add. The universe is nothing if not ironic, we suppose.

The content of this article is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of qualified health providers with questions you may have regarding medical conditions.  

All “explainer” articles are confirmed by fact checkers to be correct at time of publishing. Text, images, and links may be edited, removed, or added to at a later date to keep information current.  


ARTICLE POSTED IN

healthHealth and Medicinehealthneuroscience
  • tag
  • neuroscience,

  • nausea,

  • motion sickness

FOLLOW ONNEWSGoogele News