Activists on both sides can find studies to back up claims about the health impact of weed.
NIDA states in an email that the effect of marijuana can depend on the person (their biology) whos using it, the amount and under what circumstances.
Claiming that marijuana is less toxic than alcohol cannot be substantiated since each possess their own unique set of risks and consequences for a given individual, according to an agency email statement.
Statistics certainly paint a grim picture of the lethal impact of alcohol abuse.
The Centers for Disease Controls National Center for Health Statistics reports that there were 41,682 deaths attributed to alcohol in 2010, the last year with the most exact statistics. That breaks down to 15,990 deaths attributed to alcoholic liver disease and 25,692 other alcohol-induced deaths, excluding accidents and homicides. The center doesnt have any reports of marijuana listed as a cause of death.
Alcohol in excess is probably the No. 1 cause of toxicities from drugs of abuse in the world simply because its most widely used, Lewis-Younger said.
Robert Gable, a retired professor of psychology at Claremont Graduate University in California, compared the toxicity of 20 abused substances using reports of experimental human and animal research and on published data of overdose fatalities.
He compared the drugs by developing a safety ratio the ratio of an effective dose (eliciting a relaxed affability) to a lethal dose.
Two drinks makes you buzzy, 20 drinks puts you in the emergency room or the morgue, Gable said in a phone interview. Ten is the safety ratio for alcohol, among the most toxic recreational drugs, he said. The least physiologically toxic substances those requiring 100 to 1,000 times the effective dose to cause death included marijuana when ingested. He couldnt find any cases of documented deaths from smoked marijuana so the actual dose is a mystery.
No drug is good for teenagers, he said, but when it comes to the chances of immediate death by chemical toxicity, marijuana is about a hundred times less toxic than alcohol or cocaine.
Experts say one concern is the impact of marijuana on the brain, particularly for teens who start smoking early. Teitelbaum says marijuana can flip adolescents predisposed to mental problems into having a psychotic disorder.
Another concern in recent years: the use of synthetic marijuana, often called Spice. Health professionals caution that its vastly different from natural marijuana and more toxic.
Synthetic marijuana, however, is not marijuana.
An ad from the Marijuana Policy Project claims marijuana is less toxic than alcohol.
Science and statistics present a strong case.
We rate this claim Mostly True.