As of 2018, more than 11 million young adults reported marijuana use. After alcohol, marijuana is the most commonly used mind-altering drug in the United States. The National Institute on Drug Abuse (NIDA) refers to habitual marijuana use as “marijuana use disorder” and suggests that around 30 percent of marijuana users have some form of this disorder. Those who are exposed to THC before the age of 18 are more susceptible to marijuana use disorder than adults. Those with the disorder often feel some sort of dependence on the drug and experience withdrawal symptoms in its absence.

These symptoms include irritability, sleep disturbances, mood instability, decreased appetite, and other forms of physical discomfort within the first few weeks of quitting. “Marijuana dependence occurs when the brain adapts to large amounts of the drug by reducing the production of and sensitivity to its own endocannabinoid neurotransmitters,” states the NIDA. The brain’s adaptation to large amounts of THC is what leads researchers to the “gateway drug” theory, in which once a person becomes desensitized to the effects of marijuana they search for a stronger high in the form of hard drugs.

It is a long-held belief that smoking marijuana opens the door to other forms of substance abuse, such as heroin and cocaine. On the other hand, some purport all of these concerns to be a myth to discourage the legalization of marijuana. Many believe that marijuana use is safe and non-addicting. In reality, several factors determine an individual’s propensity to become addicted to any substance, including personality type, family history, childhood environment, and mental illness. Can a perfectly well-rounded person be hooked on drugs after developing the habit of smoking weed?

According to the NIDA, marijuana use is linked to worsening alcohol abuse and often goes hand in hand with nicotine addiction. There is also a phenomenon called “cross-sensitization.” In a laboratory experiment, rats that were administered THC and then exposed to other drugs, such as morphine, exhibited a heightened response to the stimulus. In other words, THC “primed” the rats’ brains and made them more receptive to other drugs. This could explain the link between marijuana and hard drug use. However, the NIDA also states that most people who smoke marijuana don’t go on to use other more potent substances. Additionally, cross-sensitization occurs with other substance use besides marijuana. For example, both alcohol and nicotine have the same priming effects on the brain as THC.

Alternative to the gateway drug hypothesis, vulnerable demographics, such as adolescents withstanding emotional, physical, or sexual trauma, are more likely than those with stable upbringings to abuse readily available substances, whether it be nicotine or cocaine. Furthermore, people who make frequent social encounters with individuals who partake in hard drugs are more likely to try the substances for themselves. However, the NIDA states that further research is needed to explore this possibility.

In 2016, Robert L. DuPont, president of the Institute for Behavior and Health and former director of the NIDA, wrote that people who abuse marijuana are three times more likely to become addicted to heroin. Consequently, DuPont argues against the legalization and social tolerance of weed. In his opinion, legal marijuana will join alcohol and tobacco as the leading causes of preventable death in the U.S. and will exacerbate the nation’s opioid crisis.

However, as of 2019, the Substance Abuse and Mental Health Services Administration (SAMHSA), reports that while marijuana use among young people has increased over the past three years, prescription opioid abuse has decreased. Heroin use, specifically, has declined in the 18-25 age demographic throughout 2016-2018. On the other hand, while opioid use is decreasing, methamphetamine use steadily rises. However, SAMHSA has yet to mention whether or not rising marijuana use and rising methamphetamine use are connected.

Another theory as to why hard drug users often start with marijuana and alcohol, that’s just as plausible as the gateway hypothesis, is that weed and drinks are cheaper and more accessible than cocaine or heroin. Additionally, the same things that drive people to smoke and drink, such as mental illness, boredom, or social pressure, are the same reasons they try hard drugs. This doesn’t disprove the gateway hypothesis, but it does propose another angle. In 1999, the Institute of Medicine suggested that marijuana is not the most common (or the first) gateway drug that people encounter. In those who abuse hard drugs, there’s a natural progression, from adolescence to adulthood, that starts with alcohol and tobacco and eventually graduates to marijuana.

Drug policy experts Jon Caulkins, Beau Kilmer, and Mark Kleiman, argue that pot smokers are exposed to harder drugs by their dealers. The legalization of marijuana will cut the demand for weed dealers, thus separating cocaine and heroin dealers from legal marijuana sellers and limiting exposure. However, this theory isn’t conclusive.

Some researchers suggest that legal marijuana will help curb the prescription opioid epidemic as more people turn to medicinal marijuana instead of prescription pain killers to ease the effects of chronic illness. With marijuana, there is no risk of deadly overdose and little risk of addiction, unlike pain pills. Additionally, some people use marijuana to self-medicate their mental health disorders, such as depression or anxiety because they don’t have access to professional help or dislike pharmaceutical side effects.

While the gateway hypothesis is inconclusive, none of the research claims marijuana is harmless. While one might not die from a THC overdose, consuming the drug in large amounts at one time can leave a person in mental anguish by triggering panic attacks, paranoia, or hallucinations. According to Keith Humphreys, a professor of psychiatry and behavior at Stanford University, national surveys report that 10 percent of marijuana users state that they have trouble quitting the drug, smoke more than they intend to, neglect responsibilities, and have issues concerning attention, short-term memory, and motivation.

An educated public is a safer public. Whether or not evidence eventually concludes marijuana’s status as a gateway drug, what’s certain is that people – especially children – need to know what goes in their bodies. Whether it’s drug or drink, all members of the public are better off knowing its effect to determine whether or not they’re willing to put themselves at risk. Since adolescents are less likely to make sound decisions like these for themselves (the prefrontal cortex isn’t fully developed until age 25), it’s up to adults to properly educate their children. Furthermore, it’s up to policymakers to make drugs, even the legal ones, inaccessible to minors.