I don't think anyone really knows how cannabis affects the liver, to be honest. Like most drugs, it can affect different people different ways. And, as is usually the case, there've not been any studies to really look at the effects. Seems a lot more likely that it's something else that's affecting your liver than cannabis, however.

OK, you said you don't drink. Have you by any chance ever been exposed to any type of hepatitis? Are you overweight or has your weight changed (increased) recently? Do you by any chance have gallstones? Read the link below and see if any of that information fits in your case.

Elevated liver enzymes: What does it mean? - MayoClinic.com

I have elevated liver enzymes every time they test my blood. Have since I was a young adult. So do my sister and my father. We have something called Gilbert's Syndrome, which simply means elevated liver enzymes but nothing actually wrong with our livers. Depending on how high your blood levels were, that might be the case with you, too. It's pretty common.

Is your doctor doing further tests to see what the problem is? Were the levels high enough that he was worried that you have some type of disease? Good luck in finding out what's up!