Key Takeaways
- A cross-sectional study of 1,197 dental patients in Yemen found that habitual khat chewing was associated with smoking, periodontitis, and larger oral reactive hyperplastic lesions.
- Lesions larger than 1 cm occurred more often among habitual khat chewers, but the study cannot determine whether khat caused the lesions to enlarge.
- Oral reactive hyperplastic lesions are generally benign responses to chronic irritation; readers should not interpret the findings as evidence that khat causes oral cancer.
- The study adds clinically useful information about lesion characteristics, but it appears to analyze the same 1,197-patient sampling frame described in an earlier 2025 publication rather than provide an independent replication.
- Smoking, periodontal inflammation, oral hygiene, cheek biting, tooth grinding, and other local irritants can overlap with khat use and complicate causal interpretation.
- The findings support careful oral examination, periodontal assessment, risk-factor counseling, and biopsy when clinicians cannot diagnose a lesion confidently from its clinical appearance.
- Researchers still need longitudinal studies to determine whether khat chewing directly contributes to lesion development and periodontal damage over time.
Introduction
Khat chewing is a longstanding social practice in Yemen. A recent study examined associations between habitual khat use and reactive oral lesions.
Khat, also called qat, is a plant whose fresh leaves are chewed for their stimulant effects. The practice has longstanding social and cultural importance in Yemen and parts of East Africa. During a chewing session, a bundle of leaves may remain against one side of the oral cavity for several hours. This creates a combination of repeated mechanical pressure, chemical exposure, reduced salivary comfort, and prolonged contact with the gingiva and buccal mucosa.
A new study published in Clinical, Cosmetic and Investigational Dentistry examined the association between habitual khat chewing and oral reactive hyperplastic lesions in a Yemeni dental population. The researchers reported significant associations between habitual chewing and male sex, smoking, periodontitis, and lesion size. In particular, khat chewers presented more often with lesions larger than 1 cm (Al-Ashwal et al., 2026).
The findings deserve attention, but they also require careful interpretation. A statistical association does not show that khat directly caused a lesion or made it grow. The study does not establish a biological progression from khat exposure to cancer, and it does not separate khat completely from smoking, periodontal disease, poor oral hygiene, and other sources of chronic irritation.
In clinical dentistry, a visible oral growth can appear alarming to a patient even when it represents a benign reactive process. The responsible question is not whether khat is “safe” or “dangerous” in the abstract. The more useful questions are what this study measured, how convincingly it isolated the effect of khat, and what dentists should do differently when examining patients who chew it.
What Did the New Study Examine?
Al-Ashwal and colleagues conducted a cross-sectional clinicopathological study involving 1,197 Yemeni patients who attended university dental clinics and public hospitals. The investigators evaluated habitual khat chewing alongside demographic, behavioral, periodontal, and lesion-related variables (Al-Ashwal et al., 2026).
The study focused on oral reactive hyperplastic lesions. These are localized tissue overgrowths that usually develop in response to persistent low-grade irritation or inflammation. Common examples include focal fibrous hyperplasia, pyogenic granuloma, peripheral ossifying fibroma, and peripheral giant cell granuloma. Although these conditions differ histologically, they can overlap in clinical appearance and may resemble neoplastic disease.
The researchers reported that habitual khat chewing was significantly associated with:
- male sex;
- smoking;
- periodontitis; and
- lesion size, with lesions larger than 1 cm occurring more frequently among habitual chewers.
These findings suggest that khat chewing may identify a group of patients with a heavier burden of local irritation and periodontal damage. They do not, however, show which factor came first or whether khat independently produced the observed lesions.
Why Does Lesion Size Matter?
The association with lesions larger than 1 cm is arguably the most newsworthy finding. Size can affect function, bleeding, discomfort, treatment complexity, and the urgency of diagnostic evaluation. A larger lesion may also reflect longer exposure to an irritant, delayed care, repeated trauma, or more persistent inflammation.
However, size is not a diagnosis. A large reactive lesion is not automatically malignant, just as a small lesion is not automatically harmless. Lesion dimensions can also depend on how long the patient waited before seeking care, whether the lesion was repeatedly traumatized, and whether local causes such as calculus, a fractured tooth, cheek biting, or an ill-fitting restoration remained untreated.
The study therefore supports a clinical signal rather than a causal conclusion: patients who habitually chew khat may present with larger reactive lesions and deserve careful assessment. It does not prove that khat accelerates lesion growth.
What Does the Study Actually Prove?
The study shows that, within the examined clinical population, habitual khat chewing and several adverse oral findings occurred together more often than expected by chance. This is useful observational evidence because it comes from a setting in which khat exposure is common and clinically relevant.
The findings also fit a biologically plausible model. Leaves held in the same area for hours can create chronic friction and compression. Chemical constituents and contaminants may add irritation, while dryness and changes in oral hygiene behavior may alter the local environment. Previous research has found white mucosal changes, pigmentation, gingival recession, attachment loss, and other site-specific findings among khat chewers (Yarom et al., 2010). A systematic review of periodontal studies likewise concluded that much of the available evidence points toward periodontal damage, although the studies were heterogeneous and could not establish causality confidently (Kalakonda et al., 2017).
The new study strengthens the argument that dentists should document khat use as a relevant oral-health exposure. It does not establish khat as the sole cause of reactive lesions, periodontitis, or lesion enlargement.
What Does the Study Not Prove?
First, the cross-sectional design measures exposure and disease at approximately the same point in time. It cannot establish temporality. Researchers cannot determine from these data whether habitual khat chewing preceded lesion development or whether both arose within a broader pattern of behavioral and oral-health risks.
Second, the study does not prove that khat causes oral cancer. Reactive hyperplastic lesions generally represent non-neoplastic responses to irritation. Some khat-associated white lesions may require investigation, particularly when they persist, ulcerate, become indurated, or show other suspicious features, but the presence of a reactive lesion does not establish malignant transformation. A systematic review examining potentially malignant and malignant oral disorders found that the evidence remained inconclusive because of weak study designs, small samples, inconsistent diagnostic confirmation, and inadequate control of tobacco and other confounders (El-Zaemey et al., 2015).
Third, a statistically significant association does not tell us the absolute clinical risk for an individual patient. The study does not provide a reliable prediction that a person who chews khat will develop a lesion, that an existing lesion will exceed 1 cm, or that stopping khat alone will cause the lesion to disappear.
Finally, readers should not generalize the results automatically to every population. Patterns of khat preparation, chewing duration, pesticide exposure, tobacco use, access to dentistry, oral hygiene, nutrition, and healthcare-seeking behavior may differ substantially across communities.
The Most Important Limitation: Overlapping Risk Factors
Khat chewing does not occur in isolation. In the new study, habitual khat chewing correlated with smoking and periodontitis. Both factors can influence the oral mucosa and periodontal tissues. Local irritants such as plaque, calculus, carious or fractured teeth, biting habits, and defective restorations may further contribute to reactive tissue growth.
This creates confounding. If khat chewers also smoke more often or have more periodontal inflammation, a simple comparison may attribute part of the effect of those factors to khat. P-values confirm that variables are associated; they do not show that khat independently caused the outcome.
The key question is whether the association with larger lesions remains after robust adjustment for age, sex, tobacco exposure, oral hygiene, periodontal status, lesion duration, cheek biting, tooth grinding, and other irritants. Without a clear multivariable causal model, the independent contribution of khat remains uncertain.
This does not make the study unimportant. It defines the limits of the conclusion. Khat may be a direct irritant, a marker of a cluster of risks, or both.
Is This an Independent New Dataset?
The 2026 paper reports screening 1,197 Yemeni dental patients and identifying 48 patients with histopathologically confirmed reactive hyperplastic lesions. Importantly, the authors state in the methods that this 48-patient cohort had previously been used to report the prevalence of oral reactive hyperplastic lesions.
That earlier 2025 publication by Rajeh and colleagues also reported screening 1,197 Yemeni dental patients and identifying 48 reactive hyperplastic lesions. The earlier study focused primarily on lesion prevalence and associated risk factors, whereas the 2026 paper provides a more focused clinicopathological analysis of khat-chewing status, including its association with lesion size.
The 2026 findings should therefore not be treated as an independent replication in a separate patient population. Instead, the paper provides an additional analysis of a previously reported lesion cohort.
This distinction matters when weighing the evidence. A secondary or expanded analysis of an existing cohort can provide useful new information, but it does not carry the same evidentiary weight as reproducing the findings independently in a new population.
How Does the Study Compare With Previous Research?
The new findings broadly align with earlier evidence showing localized mucosal and periodontal changes among khat chewers. Yarom and colleagues found white changes in 83% of habitual chewers compared with 16% of controls. The changes appeared mainly at the chewing site. The investigators also observed greater gingival recession on the chewing side, even though some inflammatory indices were lower there (Yarom et al., 2010).
That apparently contradictory pattern is important. Mechanical contact may remove some plaque or alter visible inflammation while still contributing to recession and attachment loss. Dentists cannot assess periodontal health from one index alone.
The 2017 systematic review found that most included studies linked khat chewing with periodontal deterioration, but differences in diagnostic criteria, exposure definitions, populations, and study quality prevented a firm causal conclusion (Kalakonda et al., 2017). The new Yemeni analysis is consistent with that pattern because habitual chewing was associated with periodontitis. It does not resolve the methodological weaknesses identified by the review.
The study is therefore better understood as reinforcement of an existing concern, not a definitive breakthrough proving a new disease mechanism.
What Should Dentists Do Differently?
The most immediate implication is better history-taking. Dentists who serve patients from Yemen, Ethiopia, Somalia, Kenya, and other communities where khat use occurs should ask about it respectfully and without stigma. Relevant questions include frequency, years of use, duration of each session, the usual chewing side, tobacco use, and whether the patient has noticed a persistent growth, white patch, ulcer, bleeding, recession, mobility, or pain.
The oral examination should compare the chewing and non-chewing sides and document:
- lesion location, dimensions, color, surface, consistency, and duration;
- ulceration, bleeding, fixation, induration, or rapid enlargement;
- plaque, calculus, gingival recession, probing depths, and attachment loss;
- sharp teeth, defective restorations, biting trauma, and other local irritants; and
- cervical lymph nodes and other findings when clinically indicated.
Management should address the lesion and its possible causes. Removing plaque, calculus, trauma, and other local irritants may be necessary, but clinicians should not assume that risk-factor modification replaces diagnosis. A persistent, enlarging, ulcerated, indurated, unexplained, or clinically ambiguous lesion may require referral and histopathologic examination.
What Should Patients Understand?
Patients should not interpret the study as proof that every person who chews khat will develop periodontal disease, a large oral lesion, or cancer. The more accurate message is that habitual chewing is associated with oral changes that may remain painless and may be overlooked.
A painless growth still deserves evaluation. Patients should seek dental care for a lump, white or red patch, non-healing ulcer, unexplained bleeding, progressive gum recession, tooth mobility, or any change that persists or enlarges. Early assessment can identify a removable irritant, guide periodontal treatment, and determine whether biopsy is necessary.
Counseling should remain culturally respectful. Clinicians can explain the observed associations, identify the patient’s individual risk factors, and support reduction or cessation without treating a longstanding social practice as a moral failing.
What Research Is Needed Next?
Future studies should follow exposed and unexposed participants over time. They should define khat exposure by frequency, session duration, years of use, chewing side, quantity, and concurrent tobacco use. Standardized periodontal measurements and histopathologic confirmation would make results easier to compare.
Researchers should also use multivariable models to distinguish the effects of khat from smoking, oral hygiene, periodontitis, age, sex, socioeconomic conditions, biting habits, and access to care. Recording lesion onset, growth, treatment, recurrence, and changes after khat cessation would help clarify temporality and reversibility.
The most convincing next step would be an independent prospective cohort in a different clinical population. That design could determine whether khat exposure predicts new lesions or periodontal deterioration rather than simply accompanying them at one examination.
Final Thoughts
The new study draws attention to a clinically important but underrecognized exposure. The researchers found associations between habitual khat chewing, periodontitis, and larger oral reactive hyperplastic lesions in a Yemeni dental population. For dentists, that is sufficient reason to ask about khat, examine the habitual chewing site carefully, and address overlapping periodontal and behavioral risks.
The evidence does not justify stronger claims. The study is cross-sectional, the relevant risk factors overlap, and the sampling frame appears to duplicate an earlier report. It does not prove that khat independently causes lesion enlargement, and it does not demonstrate malignant transformation.
Its contribution is more precise: khat chewing may help identify patients who need closer mucosal and periodontal evaluation. The next scientific task is to determine how much of that risk belongs to khat itself, how much reflects coexisting exposures, and whether reducing or stopping the habit changes clinical outcomes.
Frequently Asked Questions
What Is Khat?
Khat, or qat, is a plant whose fresh leaves are chewed for stimulant effects. The practice is common in parts of Yemen and East Africa and also occurs within diaspora communities.
Are Oral Reactive Hyperplastic Lesions Cancerous?
They are generally benign tissue responses to chronic irritation or inflammation. However, several benign, potentially malignant, and malignant conditions can look similar clinically. A dentist or oral specialist may recommend biopsy when the diagnosis is uncertain.
Does This Study Prove That Khat Causes Oral Cancer?
No. The study examined associations with reactive lesions, lesion size, and periodontal findings. It did not establish that khat causes cancer or that reactive lesions progress to cancer.
Why Might Khat Affect the Mouth?
Possible mechanisms include prolonged friction and pressure at the chewing site, chemical irritation, dryness, changes in hygiene behavior, and overlapping tobacco exposure. The study did not determine which mechanism produced the observed associations.
When Should a Patient Seek Evaluation?
A patient should arrange a dental or medical evaluation for an oral lump, persistent white or red patch, ulcer that does not heal, unexplained bleeding, rapid enlargement, induration, progressive recession, or tooth mobility. Clinical appearance alone may not provide a definitive diagnosis.
References
Al-Ashwal, A. M., Rajeh, S. A. Y., Jubarah, R., Al Moaleem, M. M., Al-Affari, H. G., Khaled, A., & Sayal, L. (2026). Association between habitual khat (Catha edulis) chewing and oral reactive hyperplastic lesions: A cross-sectional clinicopathological study in Yemen. Clinical, Cosmetic and Investigational Dentistry, 18, 640334. https://doi.org/10.2147/CCIDE.S640334
El-Zaemey, S., Schüz, J., & Leon, M. E. (2015). Qat chewing and risk of potentially malignant and malignant oral disorders: A systematic review. The International Journal of Occupational and Environmental Medicine, 6(3), 129–143. https://pubmed.ncbi.nlm.nih.gov/26174990/
Kalakonda, B., Al-Maweri, S. A., Al-Shamiri, H. M., Ijaz, A., Gamal, S., & Dhaifullah, E. (2017). Is khat (Catha edulis) chewing a risk factor for periodontal diseases? A systematic review. Journal of Clinical and Experimental Dentistry, 9(10), e1264–e1270. https://doi.org/10.4317/jced.54163
Rajeh, S. A. Y., Al-Shamahy, H. A., & Al-Kibsi, T. A. (2025). Prevalence of oral reactive hyperplastic lesions and associated risk factors in a sample of Yemeni dental patients in several universities and public hospitals. Universal Journal of Pharmaceutical Research, 10(3), 7–14. https://doi.org/10.22270/ujpr.v10i3.1346
Yarom, N., Epstein, J., Levi, H., Porat, D., Kaufman, E., & Gorsky, M. (2010). Oral manifestations of habitual khat chewing: A case-control study. Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontology, 109(6), e60–e66. https://doi.org/10.1016/j.tripleo.2010.02.022
Conflict of Interest
The author declares no conflict of interest relevant to this article.
Funding
No external funding was received for this article.
