Regular marijuana use appears to raise the risk of moderate to severe liver fibrosis, or liver scarring, among patients with chronic hepatitis C, according to new research.

Researcher Norah Terrault, M.D., of the University of California at San Francisco and colleagues said that based on the results, regular marijuana use should be discouraged among hepatitis C patients. "It is essential that we identify risk factors that can be modified to prevent and/or lessen the progression of HCV to fibrosis, cirrhosis and even liver cancer," said Terrault. "These complications of chronic HCV infection will significantly contribute to the overall burden of liver disease in the U.S. and will continue to increase in the next decade."

The warning is especially noteworthy because some hepatitis C patients have been known to switch from moderate to heavy alcohol use to marijuana use after being diagnosed. Non-daily marijuana use did not appear to have the same negative impact on liver fibrosis, researchers said.

The study was published in the journal Clinical Gastroenterology and Hepatology