The most common are various foods, infections (such as colds), menstruation, extreme physical exertion, lack of sleep, and psychological stresses, both positive and negative.An affected person may also be light-sensitive (photophobic), sound-sensitive (phonophobic) or, less frequently, temperature- or pressure-sensitive during an attack. Some people also have a strong urge to bathe in warm or cold water. In fact, many people with CVS experience a compulsion to be submerged in hot water, and end up taking several baths during the duration of an episode. For some the psychological compulsion to be in hot water is so extreme that they cannot stop themselves from taking very long baths in near scalding hot water several times per day. For some of these people, they may have just finished taking a lengthy bath in extremely hot water and immediately feel this compulsion again and end up taking another bath right after drying off. Some people with the condition experience insomnia, diarrhea (GI complications), hot and cold flashes, and excessive sweating before an episode. Some report that they experience a restless sensation or stinging pain along the spine, hands, and feet followed by weakness in both legs. Some of these symptoms may be due to dehydration or hypokalemia from excessive vomiting, rather than the underlying cause of CVS. Genetics
There is no known genetic pathogenesis for CVS. Recent studies suggest many affected individuals have a family history of related conditions, such as migraines, psychiatric disorders and gastrointestinal disorders. Inheritance is thought to be maternal, a possible genetic mitochondrial inheritance.
Adolescents show higher possible mitochondrial inheritance and maternal inheritance than found in adults. Single base-pair and DNA rearrangements in the mitochondrial DNA (mtDNA) have been associated with these traits. Diagnosis
The cause of CVS has not been determined and there are no diagnostic tests for CVS. Several other medical conditions, such as cannabinoid hyperemesis syndrome (CHS), can mimic the same symptoms, and it is important to rule these out. If all other possible causes have been excluded, a diagnosis of CVS using Rome criteria by a physician may be appropriate.Once formal investigations to rule out gastrointestinal or other causes have been conducted, these tests do not need to be repeated in the event of future episodes. Diagnostic criteria
Due to the lack of specific biomarkers available for the disorder, and if all other possible causes can be ruled out (such as intestinal malrotation), physicians rely on the Rome IV process criteria in order to diagnose patients. Patients must meet all three of the following criteria to receive diagnosis: 

Stereotypical episodes of acute vomiting each with a duration of less than 1 week
A history of at least three discrete episodes in the prior year and at least two episodes in the past 6 months, each occurring at least 1 week apart
An absence of vomiting between episodes, but other milder symptoms can be present between cyclesCriteria must be fulfilled for the last 3 months with symptom onset at least 6 months prior to diagnosis. A history of family history of migraine headaches can also be used in facilitating diagnosis.