Association between Active Pulmonary Tuberculosis and History of Cannabis Use

Abstract

Tuberculosis (TB) is a chronic lung disease caused by Mycobacterium tuberculosis. Tobacco smoking and sharing of instruments have been reported to increase TB risk. In 2022, cannabis was legalized in Thailand. Cannabis use can increase inflammatory responses in the respiratory tract. Sharing of cannabis waterpipes has also been anecdotally linked to increased tuberculosis risks. In this thesis, we conducted two studies to assess the increased TB risks at the population level in Thailand. First, using a national in-patient databank, we aimed to 1) describe the spatiotemporal correlation between cannabis-related and tuberculosis hospital admissions, and 2) compare the rate of subsequent pulmonary tuberculosis admission between those with admissions for cannabis-related causes and those without. In the second part, a case-control study using pulmonary TB cases and neighborhood-age-sex matched healthy controls was conducted in the Songkhla province of Southern Thailand in 2023 to compare their history of cannabis consumption. The national databank study indicated a decline in TB admissions alongside a rise in cannabis-related admissions. Detailed temporal analysis showed no significant lag association between the two. However, the two types of admissions correlated had a hotspot zone in Northeastern Thailand. On the matched cohort of the in-patients, the incidence density rate of subsequent TB admissions was not significantly different between that in the cannabisrelated admission cohort and that in the control non-cannabis cohort (hazard ratio: 1.48, P = 0.268). Similarly, in the case-control study, there was no significant difference in the history of oral (odds ratio of 0.65; 95% CI: 0.28–1.52), and general smoking cannabis consumptions (odds ratio of 0.72; 95% CI: 0.04–12.38) between the TB cases and their matched control. However, the TB cases had a higher prevalence of sharing bong in smoking cannabis than the control did with an odds ratio of 4.22 (95% CI: 1.47–12.07). The population-attributable fraction of this type of exposure was 12.16, close to that of tobacco smoking (PAF = 12.62). In conclusion, education should be provided to the population to reduce bong sharing among the cannabis users.