"You can die binge-drinking five minutes after you've been exposed to alcohol. That isn't going to happen with marijuana," said Ruben Baler, a health scientist at the National Institute on Drug Abuse. "The impact of marijuana use is much subtler."
(Of course, subtle effects don't equate with no danger, as is the case with smoking cigarettes, which is linked with 440,000 deaths per year in the U.S.)
Marijuana affects the cardiovascular system, increasing heart rate and blood pressure, but a person can't fatally overdose on pot like they can with alcohol, Baler said.
Alcohol is more likely than marijuana to interact with other drugs. The way that alcohol is metabolized, or broken down, in the body, is common to many drugs that are taken for a variety of conditions, said Gary Murray, acting director of the Division of Metabolism and Health Effects at the National Institute on Alcohol Abuse and Alcoholism.
This means that for people taking drugs or medications while drinking, the alcohol can increase or decrease levels of the active drug in the body.
"Those things can make it very hit and miss, whether you're getting an active dose of a medication," Murray said.
Still, both drugs can affect health in indirect ways, too. Because marijuana can impair coordination and balance, there is the risk of hurting oneself, particularly if someone drives or chooses to have unprotected sex while their inhibitions are lowered, Baler said. These are two areas where people using marijuana could hurt themselves for the short and long term.