Motion sickness is thought to be caused by your senses becoming conflicted. It is most often caused by travel but can also be caused by rides, watching certain types of films or computer games.
Travel-associated motion sickness
The types of travel most likely to cause motion sickness are:
- boat and ship travel
- air travel
- car travel
- train travel
Other types of movement, such as fairground rides or swings, may also cause motion sickness.
Motion sickness without travel
Motion sickness can sometimes occur when you are not travelling. For example, there have been reports of people experiencing symptoms of motion sickness after playing fast-paced computer games, such as racing games.
This occurs because the realism of computer graphics can produce the same mismatch between visual information and the information provided by the vestibular system. Some people may also experience motion sickness while watching a film recorded on a shaky camera or while taking part in a virtual reality game or ride.
The vestibular system
To understand the causes of motion sickness, it is useful to know about the vestibular system.
The vestibular system is a complex combination of nerves, small channels and fluids inside your inner ear. It gives your brain a sense of balance and motion.
For example, if you stand up and walk towards your front door, the position of the fluids inside your vestibular system will change. The vestibular system transmits information about the changes in the position of the fluids to your brain, so that it knows exactly how and where you are moving. This allows the rest of your body to maintain balance.
Motion sickness theory
Most experts support the theory that motion sickness is caused by a conflict of information between your senses.
Your brain holds details about where you are and how you are moving. It constantly updates this with information from your eyes and vestibular system. However, if messages from these two senses conflict, your brain cannot update your current status and the resulting confusion will lead to the symptoms of motion sickness.
For example, if you are travelling by car, motion sickness can occur because your brain cannot cope with the conflicting information from your eyes and your vestibular system. Your eyes tell your brain that you are travelling at more than 30 miles an hour, but your vestibular system tells your brain that you are sitting still.
This mismatch of information can lead to the symptoms of motion sickness, such as nausea and vomiting.