Robert L. DuPont, Jr, MD, made the term “gateway drug” famous in his book Getting Tough on Gateway Drugs: a Guide for the Family.
DuPont observed that youths at his clinic often engaged in alcohol and tobacco use before proceeding on to marijuana use. He thought that psychological barriers prevented the use of hard drugs and that once a person started frequently using certain soft drugs, they would move on to using marijuana and eventually progress to other illicit drugs as well.
This book started the conversation about soft (or legal) drugs leading to the use of illegal and controlled substances, and led to what we now call the “gateway drug hypothesis.” While it seems reasonable to accept that illegal drug use is preceded by the use of less dangerous, easily accessible drugs, the reasoning behind why a person decides to use another drug is not well understood. This is potentially the reason why the gateway drug hypothesis has never progressed to the elevated status of a scientific theory.
Which Drugs Are Gateway Drugs?
Many people are inclined to call marijuana a gateway drug. The gateway hypothesis has been used to demonize marijuana when technically alcohol and tobacco are the real culprits here, as their use typically precedes that of marijuana.
Is the Gateway Drug Hypothesis Valid?
Following DuPont’s original ideas about gateway drugs, the hypothesis morphed into another concept: gateway drugs are those that change neurological responses and make the use of other illegal drugs more pleasurable. This neuroplastic reward response is thought to be the driving force behind obtaining other illicit substances.
Animal research supports this neurological change theory. Mouse models have shown that nicotine triggers a dopamine response, which increases the sense of pleasure felt during drug use; some mouse studies also suggest that these dopaminergic effects are greater in adolescent mice than in adults. There are additional studies indicating that exposure to nicotine enhances responses to cocaine and encourages increased alcohol intake. However, all of this research is considered pre-clinical. Few studies have been conducted in humans evaluating nicotine’s effect on later drug use.