It’s a theory that’s been presented as fact by marijuana foes since the Harry Anslinger era: By partaking of cannabis, humans risk being inexorably led to harder drugs like cocaine and heroin.
This “cannabis leads to harder narcotics” argument gets trotted out whenever efforts to normalize cannabis are underway, and the expansion of marijuana legalization across North America has predictably breathed new life into this old trope. So let’s settle it once and for all: Is cannabis a “gateway drug”?
On the “yes” side, the strongest evidence comes from the National Institute on Drug Abuse. “Early exposure to cannabinoids in adolescent rodents decreases the reactivity of brain dopamine reward centers later in adulthood,” reports NIDA. “To the extent that these findings generalize to humans, this could help explain the increased vulnerability for addiction to other substances of misuse later in life that most epidemiological studies have reported for people who begin marijuana use early in life.”
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NIDA also cites THC’s alleged ability to “prime” the brain for enhanced responses to other drugs, via the phenomenon known as “cross-sensitization”: “[R]ats previously administered THC show heightened behavioral response not only when further exposed to THC but also when exposed to other drugs such as morphine,” reports NIDA.
However, NIDA notes that “cross-sensitization is not unique to marijuana. Alcohol and nicotine also prime the brain for a heightened response to other drugs and are, like marijuana, also typically used before a person progresses to other, more harmful substances.”
Beyond such generalities and rat-based supposition lies the supporting evidence for the “No, cannabis is not a gateway drug” argument.