Regular marijuana use increases risk of hepatitis C-related liver damage

January 28, 2008

Patients with chronic hepatitis C (HCV) infection should not use marijuana (cannabis) daily, according to a study published in Clinical Gastroenterology and Hepatology, the official journal of the American Gastroenterological Association (AGA) Institute. Researchers found that HCV patients who used cannabis daily were at significantly higher risk of moderate to severe liver fibrosis, or tissue scarring.

Additionally, patients with moderate to heavy alcohol use combined with regular cannabis use experienced an even greater risk of liver fibrosis. The recommendation to avoid cannabis is especially important in patients who are coinfected with HCV/HIV since the progression of fibrosis is already greater in these patients.

“Hepatitis C is a major public health concern and the number of patients developing complications of chronic disease is on the rise,” according to Norah Terrault, MD, MPH, from the University of California, San Francisco and lead investigator of the study. “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. 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.”

This is the first study that evaluates the relationship between alcohol and cannabis use in patients with HCV and those coinfected with HCV/HIV. It is of great importance to disease management that physicians understand the factors influencing HCV disease severity, especially those that are potentially modifiable. The use and abuse of both alcohol and marijuana together is not an uncommon behavior. Also, individuals who are moderate and heavy users of alcohol may use cannabis as a substitute to reduce their alcohol intake, especially after receiving a diagnosis like HCV, which affects their liver.

Researchers found a significant association between daily versus non-daily cannabis use and moderate to severe fibrosis when reviewing this factor alone. Other factors contributing to increased fibrosis included age at enrollment, lifetime duration of alcohol use, lifetime duration of moderate to heavy alcohol use and necroinflammatory score (stage of fibrosis). In reviewing combined factors, there was a strong (nearly 7-fold higher risk) and independent relationship between daily cannabis use and moderate to severe fibrosis. Gender, race, body mass index, HCV viral load and genotype, HIV coinfection, source of HCV infection, and biopsy length were not significantly associated with moderate to severe fibrosis.

Of the 328 patients screened for the study, 204 patients were included in the analysis. The baseline characteristics of those included in the study were similar to those excluded with the exception of daily cannabis use (13.7 percent of those studied used cannabis daily versus 6.45 percent of those not included). Patients who used cannabis daily had a significantly lower body mass index than non-daily users (25.2 versus 26.4), were more likely to be using medically prescribed cannabis (57.1 percent versus 8.79 percent), and more likely to have HIV coinfection (39.3 percent versus 18.2 percent).

The prevalence of cannabis use amongst adults in the U.S. is estimated to be almost 4 percent. Regular use has increased in certain population subgroups, including those aged 18 to 29.

Hepatitis is an inflammation of the liver. Hepatitis C is the most common form of hepatitis and infects nearly 4 million people in the U.S., with an estimated 150,000 new cases diagnosed each year. While it can be spread through blood transfusions and contaminated needles, for a substantial number of patients, the cause is unknown. This form of viral hepatitis may lead to cirrhosis, or scarring, of the liver. Coinfection of hepatitis C in patients who are HIV positive is common; about one quarter of patients infected with HIV are infected with hepatitis C. The majority of these patients, 50 to 90 percent, were infected through injection drug use. Hepatitis C ranks with alcohol abuse as the most common cause of chronic liver disease and leads to about 1,000 liver transplants yearly in the U.S.

Source: American Gastroenterological Association

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