Does Science Still Believe that Gateway Drugs can Lead to Addiction?
We’ve been hearing this for decades: marijuana is a gateway drug. Our parents told us this over and over again, but what does science say?
f you grew up as part of the D.A.R.E. generation — kids of the 1980s and ’90s who learned about drugs from alarmist public service announcements — you know all too well the dangers of so-called gateway drugs. Go to bed with marijuana or beer, you were taught, and risk waking up with cocaine or heroin.
Three decades later, scientists and politicians still debate whether using “soft” drugs necessarily leads a person down a slippery slope to the harder stuff. Critics note that marijuana has, in some cases, been shown to actually prevent people from abusing other substances. And even D.A.R.E. now acknowledges that the overwhelming majority of people who smoke pot or drink never graduate to pills and powders.
But new research is breathing fresh life into the perennially controversial theory, and the timing seems apt. As marijuana legalization and the opioid epidemic sweep across the country, parents are once again questioning the root causes of addiction. And politicians opposed to legalization, including Attorney General Jeff Sessions and Gov. Chris Christie of New Jersey, have routinely used the gateway effect as their chief argument against reform.
There’s enough research suggesting that marijuana use is likely to precede use of other licit and illicit substances. This therefore, seems to support the argument that use of some substances and fuel thee development of addiction to other substances.
In fact, there was a study using longitudinal data from the National Epidemiological Study of Alcohol Use and Related Disorders that found that adults who reported marijuana use during the first wave of the survey were more likely than adults who did not use marijuana to develop an alcohol use disorder within three years.
People who used marijuana and already had an alcohol use disorder at the outset were found to be at even greater risk of their alcohol use disorder worsening. Marijuana use is also linked to other substance use disorders including nicotine addiction.
Early exposure to cannabinoids in adolescent rodents decreases the reactivity of brain dopamine reward centers later in adulthood. 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. It is also consistent with animal experiments showing THC’s ability to “prime” the brain for enhanced responses to other drugs. For example, rats previously administered THC show heightened behavioral response not only when further exposed to THC but also when exposed to other drugs such as morphine—a phenomenon called cross-sensitization. In November of 2017, Columbia University study published in “Science Advances” showed that rats exposed to alcohol were far more likely than other rats to push a lever that released cocaine. The researchers also found that the alcohol suppressed two genes that normally act as cutoff switches for the effects of cocaine, creating a “permissive environment” for the drug within the rodents’ brains. These findings are consistent with the idea of marijuana as a “gateway drug.” However, the majority of people who use marijuana do not go on to use other, “harder” substances. Also, 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. It is important to note that other factors besides biological mechanisms, such as a person’s social environment, are also critical in a person’s risk for drug use. An alternative to the gateway-drug hypothesis is that people who are more vulnerable to drug-taking are simply more likely to start with readily available substances such as marijuana, tobacco, or alcohol, and their subsequent social interactions with others who use drugs increases their chances of trying other drugs. Although further research is needed to explore this question, there’s still enough evidence to support the notion that using marijuana as a higher probability of a person delving into other substances. Today, with widespread legalization of marijuana, there’s certainly not enough data to gauge what will happen over the next 25-50 years. It’s no secret that parental norms have changed as society has become more politically correct. This practice of being soft on children and young adults has changed the way subsequent generations think about vices. It’s a dangerous, slippery slope between parenting with love and watching a child self destruct. Most would agree that there’s strong scientific evidence to support the notion that gateway drugs are a real concern.