Inverse association of marijuana use with nonalcoholic fatty liver disease among adults in the United States

BACKGROUND & AIMS The impact of marijuana on nonalcoholic fatty liver disease (NAFLD) is largely unknown. We studied the association between marijuana and NAFLD utilizing cross-sectional data from the National Health and Nutrition Examination Survey (NHANES) from 2005-2014 and NHANES III (1988-1994). METHODS Suspected NAFLD was diagnosed if serum alanine aminotransferase (ALT) was > 30 IU/L for men and > 19 IU/L for women in the absence of other liver diseases (NHANES 2005-2014). In NHANES III cohort, NAFLD was defined based on ultrasonography. RESULTS Of the 14,080 (NHANES 2005-2014) and 8,286 (NHANES III) participants, prevalence of suspected NAFLD and ultrasonographically-diagnosed NAFLD were inversely associated with marijuana use (p < 0.001). Compared to marijuana-naïve participants, marijuana users were less likely to have suspected NAFLD (odds ratio [OR]: 0.90, 95% confidence interval [CI]: 0.82-0.99 for past user; OR: 0.68, 95% CI: 0.58-0.80 for current user) and ultrasonographically-diagnosed NAFLD (OR: 0.75, 95% CI: 0.57-0.98 for current user) in the age, gender, ethnicity-adjusted model. On multivariate analysis, the ORs for suspected NAFLD comparing current light or heavy users to non-users were 0.76 (95% CI 0.58-0.98) and 0.70 (95% CI 0.56-0.89), respectively (P for trend = 0.001) with similar trends in ultrasonographically-diagnosed NAFLD (OR: 0.77, 95% CI: 0.59-1.00 for current user; OR: 0.71, 95% CI: 0.51-0.97 for current light user). In insulin resistance-adjusted model, marijuana use remained an independent predictor of lower risk of suspected NAFLD. CONCLUSIONS In this nationally representative sample, active marijuana use provided a protective effect against NAFLD independent of known metabolic risk factors. The pathophysiology is unclear and warrants further investigation.