The factors that contribute to motion sickness are not well understood, but susceptibility to the condition does seem to be partly genetic. When motion sickness occurs, it likely results from a mismatch in signals about movement coming from different parts of the body. The brain senses movement by combining signals from the , eyes, muscles, and joints. When the eyes signal to the brain that the body is still (for example, a moving car appears stationary to the person riding in it), but the inner ears & other parts of the body signal that the body is in motion, a conflict occurs. Researchers believe it is this sensory conflict that triggers the symptoms of motion sickness. The mechanism by which a sensory mismatch could lead to dizziness, nausea, & related symptoms is unclear, & other explanations for motion sickness are also being explored.
Common, complex conditions such as motion sickness are often polygenic, which means they involve variations in many genes. However, little is known about the specific genes involved in motion sickness because few studies have been done to identify them.
One study compared genetic variations in a large number of people with & without a susceptibility to motion sickness. The researchers found common genetic variations in or near 35 genes that may be associated with the condition. These genes play a wide variety of roles in the body: some are involved in eye & ear development, & others in the formation of otoliths, which are tiny structures in the inner ear that are involved in sensing gravity & movement. Still other identified genes play roles in the development & function of junctions between nerve cells () where cell-to-cell communication takes place, & in the way the body processes the simple sugar glucose & the hormone , which helps regulate blood sugar levels. Additional research will be necessary to confirm the association between variations in specific genes & motion sickness susceptibility.