Motion sickness is a common phenomenon experienced when the brain receives conflicting signals about movement from different parts of the body. This often occurs during travel in vehicles like cars, boats, or airplanes, where visual input might suggest stillness while the inner ear senses motion. Symptoms can vary in severity and typically include nausea, vomiting, dizziness, headache, excessive salivation, and a cold sweat.
The Hereditary Link
Evidence suggests that motion sickness often has a hereditary component, tending to cluster within families. Individuals with a susceptible first-degree relative, such as a parent or sibling, are more likely to experience it. Research, including a 2005 study, found that if one identical twin was affected, the other was highly likely to be as well. Furthermore, children of parents prone to motion sickness were five times more likely to experience it. Genetic factors account for up to 70 percent of an individual’s risk for motion sickness.
Genetic Influences and Mechanisms
The underlying mechanism of motion sickness involves the brain’s interpretation of sensory conflict, where signals from the eyes, inner ear’s vestibular system, and body receptors provide contradictory information about motion. For instance, inside a moving vehicle, eyes may perceive stillness while the inner ear detects motion, and individuals who have a complete absence of a functional vestibular apparatus are typically immune, underscoring its central role. Recent genome-wide association studies (GWAS) have identified specific genetic variations, or single-nucleotide polymorphisms (SNPs), linked to susceptibility. These variations are often found near genes involved in the development and function of balance organs, eyes, and ears, and some also affect neurological processes and glucose metabolism. Notably, some genetic factors exhibit sex-specific effects, appearing up to three times stronger in women.
Beyond Genetics: Other Contributing Factors
While genetics play a role, many other factors can influence an individual’s susceptibility to motion sickness. Environmental elements, such as the specific type of motion encountered (e.g., car, boat, or plane), reading in a moving vehicle, limited ventilation, strong smells, or crowded spaces, can trigger symptoms. Age is another significant factor, with children between 2 and 12 years old generally being more susceptible; susceptibility tends to decrease with advancing age. Hormonal fluctuations, such as those occurring during pregnancy, menstruation, or due to oral contraceptive use, can further increase susceptibility in women. Psychological aspects, such as anxiety, fear, or even the expectation of feeling sick, can significantly influence the onset and severity, and certain medical conditions like migraines or vertigo are also associated with increased likelihood.
Understanding Individual Susceptibility
Individual susceptibility to motion sickness arises from a complex interplay between inherited genetic predispositions and various non-genetic factors. The condition is considered polygenic, meaning it involves the subtle influence of variations across multiple genes rather than a single gene. This genetic blueprint sets a baseline for how an individual’s brain processes and integrates sensory information related to motion. Environmental triggers, along with factors like age, hormonal status, and psychological states, can significantly modify this innate predisposition. The precise combination of these elements determines how readily and severely an individual will experience motion sickness.