Andrew Morral, PhD, Director of the Safety and Justice Program in Infrastructure, Safety, and Environment at the RAND Corporation, stated in a Dec. 2, 2002 press release discussing his study with the RAND Corporation published in the British journal Addiction in 2002:

“We’ve shown that the marijuana gateway effect is not the best explanation for the link between marijuana use and the use of harder drugs.

An alternative, simpler and more compelling explanation accounts for the pattern of drug use you see in this country, without resort to any gateway effects. While the gateway theory has enjoyed popular acceptance, scientists have always had their doubts. Our study shows that these doubts are justified…

The people who are predisposed to use drugs and have the opportunity to use drugs are more likely than others to use both marijuana and harder drugs. Marijuana typically comes first because it is more available.”

Dec. 2, 2002