British experts evaluated substances including alcohol, cocaine, heroin, Ecstasy and marijuana, ranking them based on how destructive they are to the individual who takes them and to society as a whole, and determined that alcohol is more dangerous than illegal drugs like heroin and crack cocaine.

Researchers analyzed how addictive a drug is and how it harms the human body, in addition to other criteria like environmental damage caused by the drug, its role in breaking up families and its economic costs, such as health care, social services, and prison.

Heroin, crack cocaine and methamphetamine were the most lethal to individuals. When considering their wider social effects, alcohol, heroin and crack cocaine were the deadliest. But overall, alcohol outranked all other substances, followed by heroin and crack cocaine.

Experts said the study should prompt countries to reconsider how they classify drugs.

“What governments decide is illegal is not always based on science,” said Wim van den Brink, professor of psychiatry and addiction at the University of Amsterdam. “Drugs that are legal cause at least as much damage, if not more, than drugs that are illicit,” he said.