By Jennifer Brown
Functional Gastrointestinal Disorders and Chronic Nausea
Typical gastrointestinal disorders involve structural and physiological abnormality; however, functional gastrointestinal disorders (FGID) have not been found to have an organic cause to date (Mousavi et al., 2023). Despite these differences, both types of gastrointestinal disorders can be associated with chronic gastrointestinal symptoms, such as chronic nausea. Specifically, research has now shown that nausea may also have an underlying functional etiology. That is, a dysregulation of the gut and brain pathways can cause chronic nausea. However, deciphering between organic and functional causes of gastrointestinal disorders and their associated symptoms can be difficult, especially with the limited research that is currently available. Thus, the following is an exploratory discussion into functional gastrointestinal disorders and nausea-related symptoms based on my experiences with chronic unexplained nausea.
The Rome III classification system
Per Drossman (2006), nonstructural symptoms, or symptoms with no visible underlying structural disease, are "functional." Like other functional disorders, such as functional neurological disorders, functional gastrointestinal disorders are perceived as psychological; however, that perception is changing (Drossman, 2006). Specifically, researchers are now emphasizing the bidirectional relationship between the brain and gut, known as the gut-brain interaction (DGBI). The Rome Foundation has created consensus-based criteria, known as the Rome criteria, to categorize and diagnose the different types of FGIDs, which include functional vomiting, diarrhea, constipation, and chronic idiopathic nausea, among many others (Drossman, 2006; Mousavi et al., 2023). FGIDs often involve physiological changes such as increased motor reactivity, enhanced visual hypersensitivity, and altered inflammatory and CNS (central nervous system)-enteric nervous system regulation (Drossman, 2006). Importantly, however, each category of FGIDs has its own theorized etiology.
Chronic unexplained nausea
Among FGIDs, chronic unexplained nausea falls under the Rome III criteria's nausea and vomiting category (Drossman, 2006; Jung et al., 2019). This category includes idiopathic nausea, functional vomiting, cyclic vomiting syndrome, and rumination syndrome (Drossman, 2006; Jung et al., 2019). For clarity, these disorders will be described as chronic unexplained nausea/functional nausea. Accordingly, in adults, functional nausea is often described as "bothersome" nausea, usually not accompanied by vomiting; in children, it may be described as stomach pain and discomfort (Di Lorenzo, 2022; Jung et al., 2019). Nonetheless, chronic unexplained nausea in children has been associated with abdominal migraines, postural orthostatic tachycardia syndrome (POTS), and pain-related disorders (Di Lorenzo, 2022), suggesting that this condition may have more underlying medical causes or more influence on medical symptoms. This phenomenon may be especially true in cases where nausea can cause symptoms of gastroparesis and delays in gastric emptying, which, in turn, can contribute to significant medical issues if not treated.
Chronic nausea and quality of life
While nausea is a subjective experience and does not need diagnostic testing to verify, its consequential effects on quality of life are evident. I have experienced unexplained nausea for at least the past six months. I do not recall when I started to get nausea repetitively (twice or more a week), but I do know now that it can significantly affect what activities I can tolerate. For example, some family was in town a few months ago, yet I felt too nauseous to participate. Nausea has kept me from enjoying meaningful activities such as spending time with others, enjoyable exercises, and some of my favorite foods. As a result, I have resorted to my bed and safe foods such as broth and crackers, hoping things will settle down.
Moreover, through this process, I have learned that getting nausea medication and "help" from physicians and pharmacies is easy. Once I told my primary care doctor about my frequent nausea, I was immediately given anti-nausea medication. When the medication started not being strong enough, my doctor increased the medication. In the same way, pharmacies and drug stores now have a vast amount of anti-nausea/nausea relief products, ranging from anti-nausea ginger gum to gummies and candy to wristbands with pressure point therapy. All these options make me wonder if companies are making these products because of an actual need (people are more nauseous than before) or if the variety is because people will buy it (for the pleasure of buying something new and exciting).
This experience makes me wonder if my symptoms result from an underlying functional gastrointestinal disorder. While my providers have not suggested that is the root cause of my symptoms, I am curious if having one functional disorder, in a sense, "opens the door" for more functional disorders. As someone diagnosed with functional neurological disorder, it is understood that my neurological symptoms are due to problems with the brain and body’s communication system, just as FGIDs are with the brain and gut. If this is another functional disorder, would the same treatments work to fix these functional issues, or are they still different? These are the questions that still need to be addressed.
For more information on nausea and vomiting, go to:
For more info on functional gastrointestinal disorders, go to:
Five things you need to know about functional vomiting syndromes
Food and Drug Administration Patient-Focused Initiative
References
Di Lorenzo, C. (2022). Functional nausea is real and makes you sick. Frontiers in Pediatrics, 10: 848659. https://doi.org/10.3389/fped.2022.848659
Drossman Care. (2018). Five things you need to know about functional vomiting syndromes March 2018. https://drossmancare.com/dr-drossman-five-things-need-know-functional-vomiting-syndromes/
Drossman, D. A. (2006). The functional gastrointestinal disorders and the Rome III process. Gastroenterology, 130(5), 1377-1390. https://doi.org/10.1053/j.gastro.2006.03.008
U.S. Food and Drug Administration. The voice of the patient: Functional gastrointestinal disorders. (2016). Center for Drug Evaluation and Research (CDER) https://www.fda.gov/files/about%20fda/published/The-Voice-of-the-Patient--Functional-Gastrointestinal-Disorders.pdf
Gottfried, J. (2022). Nausea and vomiting. Merck Manual Professional Version. https://www.merckmanuals.com/professional/gastrointestinal-disorders/symptoms-of-gastrointestinal-disorders/nausea-and-vomiting
International Foundation for Gastrointestinal Disorders. (2023). Functional GI disorders. https://iffgd.org/gi-disorders/functional-gi-disorders/
Jung, H.-H., Tae, C. H., Moon, C. M., Kim, S.-E., Shiim, K.-N., & Jung, S.-A. (2019). Chronic unexplained nausea in adults: Prevalence on quality of life, and underlying organic diseases cohort of 5096 subjects comprehensively investigated. PloS ONE, 14(12): e0225264. https://doi.org/10.1371/journal.pone.0225364
Mousavi, E., Keshteli, H., Sehhati, M., Vaez, A., & Adibi, P. (2023). Re-investigation of functional gastrointestinal disorders utilizing a machine learning approach. BMC Medical Informatics and Decision Making, 23, 167.
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