We hear a lot about the effects of cannabis on the brain and body, but rarely do we consider its effects when used in combination with other drugs, like alcohol. Studying the health impacts of both alcohol and cannabis on their own is valuable, but it doesn’t always reflect the public’s use patterns. Therefore, it’s important to understand the impact that the combination of alcohol and cannabis has on health outcomes. A recent study took up this challenge by investigating the effect of cannabis consumption on alcoholic liver disease.
What Is Alcoholic Liver Disease?
Drinking a lot of alcohol over many years causes liver disease by consistently elevating levels of inflammation. Alcohol directly damages liver cells and causes an inflammatory response. Additionally, alcohol disturbs the walls of the intestine, leading to a recruitment of inflammatory cells to repair the damage. These inflammatory cells make their way through the intestine to the liver where they contribute to liver inflammation. Alcohol also disrupts the microbes in the gut, causing them to release toxins into the blood stream that the liver tries to break down and becomes inflamed in the process.
These processes lead to the onset and progression of alcoholic liver disease:
- The progression of alcoholic liver disease often brings a disruption of normal gut function, leading to an excess of fat deposits in the liver. This creates a condition known as “steatosis,” or “fatty liver.”
- The increase in the cellular stress by the excess of fat cells in the liver leads to a state of constant inflammation of the liver, even in the absence of alcohol. This state is called “alcoholic hepatitis.”
- Eventually, this inflammation leads to irreversible liver cell damage. The damage reaches a point where few healthy cells remain and the liver becomes scarred with non-functioning tissue. This stage is called “cirrhosis,” and liver function is severely compromised.
- Lastly, the ongoing inflammation for years, if not decades, also increases risk for liver cancer, called “hepatocellular carcinoma.”
These four manifestations characterize the devastating alcoholic liver disease, which turns out to be quite common. Nearly 29% of individuals have had an alcohol use disorder in their lifetime, and among them, 20% develop liver disease. And it can kill you. In fact, those with an alcohol use disorder are 23 times more likely to die from a liver disease. What if there was a way to reduce the risk of alcoholic liver disease in those with an alcohol use disorder?
Indeed there may be, and cannabis may hold the key.
Ten percent of individuals with an alcohol use disorder also have a cannabis use disorder, while even more use cannabis but aren’t classified as dependent consumers. Could cannabis’ anti-inflammatory properties protect against the development of alcoholic liver disease?
Study Findings: The Effects of Cannabis on Alcoholic Liver Disease
In a massive study that included 320,000 individuals with an alcohol use disorder* (of which over 26,000 were non-dependent cannabis users and 4,300 were dependent cannabis users), the scientists revealed that cannabis use protected against developing alcoholic liver disease.
Cannabis had less of a protective effect in those who consumed more alcohol and met the criteria for alcohol dependence.
The scientists found that regardless of whether people were frequent or infrequent cannabis consumers, cannabis protected against developing each of the four stages of liver disease. Notably, the heaviest cannabis consumers had the greatest protection against alcoholic liver disease.
Specifically, cannabis use was associated with (note: percentages are for combined dependent and non-dependent cannabis consumers):
- 45% reduction in alcoholic steatosis (fatty liver)
- 40% reduction in alcoholic hepatitis (inflamed liver)
- 55% reduction in alcoholic cirrhosis (scarred liver)
- 75% reduction in hepatocellular carcinoma (liver cancer)
It must be noted that cannabis was most protective in individuals who met the diagnostic criteria for alcohol abuse. Cannabis had less of a protective effect in those who presumably consumed more alcohol and met the criteria for alcohol dependence. Broadly speaking, alcohol abuse is drinking too much too often, while dependence is the inability to quit. In most cases, those who are dependent end up consuming more alcohol throughout their lives. So it appears that cannabis is only protective against alcoholic liver disease to a point; the more you drink, the less cannabis can help.
* Alcohol use disorder is made up of both alcohol abuse and dependence. You can generally think of alcohol abuse as drinking too much too often, while dependence is the inability to quit. Despite both being classified as an alcohol use disorder, they reflect differences in the way that alcohol affects brain functioning, as well as the changes in the brain that result from long-term consumption.
Cannabis Protects Against Liver Cancer by Reducing Inflammation
Despite the growing excitement of certain cannabinoids in cancer treatment, the scientists concluded that cannabis’ protection against liver cancer mostly came from its ability to prevent cirrhosis. This is therefore a different protective mechanism than halting or killing the cancer directly. Since 90% of hepatocellular carcinoma stems from cirrhosis, cannabis’ block of this critical step illustrates its substantial therapeutic potential to prevent the onset of these life-threatening conditions.
But their results still leave open the possibility for cannabis’ direct anti-cancer effects. The scientists report that cannabis use was associated with a similar reduction in liver cancer in both alcohol abusers and those who were dependent. Since cannabis was less effective at preventing cirrhosis in those with alcohol dependence, it leaves open the possibility that cannabis directly blocked the development of liver cancer independent of its effects on cirrhosis. Additional studies are needed to assess the effectiveness of cannabis’ anti-cancer properties in the liver.
Alcohol Increases Inflammation
Alcohol damages the brain and body by increasing inflammation, and this inflammation contributes to liver disease. The anti-inflammatory properties of the primary cannabinoids, THC and cannabidiol (CBD), lead one to predict that cannabis consumption could reduce inflammation caused by alcohol, and therefore help prevent the development of liver disease.
However, cannabis’ anti-inflammatory effects are not so straight forward in the liver. THC activates cannabinoid type I and type II receptors (CB1 and CB2), while CBD blocks THC’s actions at CB1 receptors and activates CB2 receptors. This distinction is important considering that activating CB1 receptors has pro-inflammatory effects in the liver and leads to liver disease, while CB2 activation has anti-inflammatory effects and protects against liver disease. These effects have been identified in laboratory models of liver disease, but cannabis’ effect on alcoholic liver disease in humans had not yet been assessed.
Cannabis’ anti-inflammatory properties are already being utilized for pain relief as well as treatment for colitis (inflammation of the colon), multiple sclerosis, and arthritis. Balanced THC/CBD strains or CBD-dominant strains may provide even greater anti-inflammatory effects, and hopefully better prevent alcoholic liver disease.