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What are Gateway Drugs?
The gateway drug theory states that relatively mild drugs condition the user to be more likely to become addicted to harder drugs later in life. The idea is that flooding the brain with dopamine changes the neural pathways, making them more susceptible to drug addiction.
The most common substances considered to be gateway drugs include nicotine, alcohol, and marijuana. For decades, gateway theory was influential in forming assumptions around drug addiction. However, some experts have criticized this approach in recent years, arguing it is incomplete.
History of Gateway Drugs
The idea of a progression in substance use from weaker to harder drugs goes back at least to the 1930s. Known as Stepping Stone Theory at that time, it argued there was an inevitable progression from marijuana to heroin.
In a 1975 article in the New England Journal of Medicine, researcher Denise Kandel created the Gateway Hypothesis. The key innovation was allowing for diversity in outcomes. Ala Reefer Madness, Stepping Stone Theory conceptualized the first-time user of marijuana on an irrevocable path toward harder drugs.
Gateway Theory, by contrast, recognized that not all gateway drugs are a sufficient factor in harder drug use.
Common Gateway Drugs
Common gateway drugs include:
Nicotine is one of the most common gateway drugs, followed by alcohol. It is a stimulant that provides tobacco users with a sense of mental alertness.
Nicotine is most commonly inhaled through cigarette smoke, though it can also be absorbed into the gums via snuff. It is one of the most common substances used by young people trying drugs for the first time.
Nicotine is habit-forming and is considered by some to be as addictive as heroin. The reason for this is partly due to its high accessibility and its ability to amplify pleasurable activities and make boring activities more bearable. For example, one might smoke a cigarette after eating a satisfying meal or studying for a test. This broad usefulness of nicotine to seemingly all situations makes it far more addictive than would appear.
Short-term side effects of nicotine use include:
- Increased adrenaline and mental alertness
- Reduction of anxiety
- Increased heart rate
Symptoms of nicotine withdrawal include:
- Mental sluggishness
- Increased anxiety
- A sharp increase in appetite
- Cravings for more nicotine
There is a strong link between illicit drug use and tobacco products, especially by young people. According to a 2014 study, 87.9% of young adult cocaine users had smoked cigarettes in the past.7
By contrast, only 2.9% of cocaine users had no experience with cigarettes. Studies in mice show that nicotine primed them to self-administer cocaine, but the reverse was not true. This indicates nicotine is uniquely suited to be a gateway drug.7
Another rodent study demonstrates nicotine’s biomechanical mechanisms in “priming” the brain for other illegal drugs like cocaine. The results showed that biological changes took place in the brain’s reward-seeking pathways.12
Multiple studies suggest that these effects are strongest in adolescence. This indicates that young people exposed to nicotine are particularly vulnerable to future substance use disorders (SUD).3
Illicit Substances Linked to Nicotine Use
Illicit substances linked to nicotine use include:
- Marijuana — According to a Johns Hopkins study, young people who smoked cigarettes were seven times more likely to try marijuana.
- Cocaine — Studies of mice pre-treated with nicotine show a heightened response to cocaine compared to control groups.
- Heroin — Evidence suggests nicotine primes the same receptors in the brain that respond to opioids.
Marijuana is the most commonly used drug after nicotine and alcohol and the most frequently used illegal drug overall.
Marijuana acts upon the brain through the chemical THC, a psychoactive compound that produces feelings of euphoria and heightened sense perception.
Increased appetite and altered sense of time are also common effects. It is typically smoked, though users can also ingest it.
According to the Substance Abuse and Mental Health Services Administration (SAMHSA), frequent marijuana use brings various harmful effects. In the short-term, users have reported feelings of distrust, paranoia, and low self-esteem after taking too much. There are many harmful long-term effects associated with chronic marijuana use. For example, regular use of marijuana can cause a permanent drop in IQ by as much as eight points. Habitual marijuana usage is linked to a variety of mental health disorders, such as schizophrenia and depression.
Short-term side effects of marijuana use include:
- Poor memory
- Increased appetite
- Decreased reaction time
Long-term side-effects of marijuana use include:
- Lower self-esteem
- Decreased in IQ
- Poor academic performance
- Financial difficulties
- Increased risk for mental health problems
Epidemiological studies have yielded somewhat conflicting results on marijuana’s role as a gateway drug. Some factors include availability, the user’s mental health and age, and level of potency.11
However, animal studies have shown a significant overlap in the neural pathways affected by THC and opioids. Adolescent rodents introduced to cannabis exhibited a greater preference for opioids than the control group.3
Illicit Substances Linked to Marijuana Use
Illicit substances linked to marijuana use include:
- Alcohol — Per the National Institute on Drug Abuse, marijuana users are more likely than non-users to develop alcohol use disorder (AUD).
- Heroin — According to the CDC, people addicted to marijuana are three times more likely to be addicted to heroin.
- Cocaine/Crack — Studies indicate the overwhelming majority of crack-cocaine users are also prior marijuana users
Like nicotine and cannabis, alcohol is a popular gateway drug. Alcohol is a central nervous system depressant and the active ingredient in beer, wine, and spirits. It is consumed primarily for recreation, but also for cultural and religious reasons.
When consumed, the user feels a sense of euphoria, relaxation, and increased sociability. Some other effects include a decline in fine motor skills, increased aggression, memory, and slurred speech.
Alcohol is habit-forming, and excessive consumption induces physical dependency. Alcohol use disorder (AUD), also known as alcoholism, is one of the most common substance use disorders.
According to the National Institute of Health, almost 6% of adults in 2018 experienced AUD. Thus, almost every person has the experience, either personal or through loved ones, with AUD.9
The long-term negative health effects of alcohol use disorder are numerous. According to the Centers for Disease Control and Prevention, these include:
- High blood pressure
- Increased risk of heart disease
- Increased risk of stroke
- Liver disease
Illicit Substances Linked to Alcohol Use
Illicit substances linked to alcohol use include:
- Cocaine — Per one study, alcohol, along with depression, is second only to cannabis as a predictor of future cocaine addiction.
- Marijuana — A study of twelfth graders found those who consistently used alcohol were sixteen times more likely to use marijuana.
- Nicotine — A study of twelfth graders found those who consistently used alcohol were thirteen times more likely to use nicotine.
How Gateway Drug Use Can Lead to Addiction
Research is beginning to identify the biological mechanism behind addiction.3 As highlighted earlier, has long been observed that there is a common progression in the initial use of various drugs.
Scientists have used animal studies to show the structural and chemical changes in the brain resulting from the use of gateway drugs. In fact, all used drugs share a common neural pathway. Therefore, the use of one or more of these drugs makes the person biologically more vulnerable to a substance use disorder (SUD).
The Gateway Drug Hypothesis
While known under various names since the 1930s, the term Gateway Theory was put out in 1975 by Denise Kandel. Kandel noted in two studies that those who used dangerous substances such as opioids or amphetamines progressed through stages.
Twenty-seven percent of young people who smoke marijuana originally experimented with alcohol and tobacco products. Likewise, 26% of young adults who used marijuana later progressed to LSD, amphetamines, and heroin. In other words, very few of those who used harder drugs did so without first starting with gateway drugs.
How Accurate is the Theory?
There is some controversy over the validity of Gateway Theory. The hypothesis initially did not address the causal factors behind addiction; something critics were quick to point out.
Other factors such as the environment, could just as easily be the culprit. In addition, the vast majority of users of gateway drugs do not move on to harder substances.
Risk Factors for Illicit Drug Use
Risk factors include:
- Family history of substance use disorder (SUD)
- Low academic achievement
- Poor mental health
- Negative peer groups
- Sexual abuse
- Lack of parental guidance
How to Prevent Addiction Before it Starts
To prevent addiction, it is vital to educate young people on the dangers of drugs. Studies show the adolescent brain is particularly vulnerable to developing substance use disorder.11
Parents, teachers, and other adults in the lives of young people must be made aware of the uniquely dangerous period adolescence represents for potential drug addiction.