Introduction

In this module, you will learn about the substances that are commonly referred to as “gateway drugs.” This term refers to drugs whose initial use can lead to a person experimenting with drugs that may be more addictive.

Four different substances, with varying degrees of legality, will be discussed as common gateway drugs: caffeine, alcohol, tobacco, and marijuana.

Image 4.1 – Image of Several Used Cigarette Butts

Learning Content

A drug is a chemical agent capable of producing biologic responses within the body. These responses may be desirable (therapeutic) or undesirable (adverse). The term “gateway drug” has been used to describe habit-forming drugs that may not be addictive, but could lead to the use of other addictive drugs (NIDA, Marijuana drugFacts, 2019). It is important to note that other factors are critical in a person’s risk for drug use. Biological mechanisms and social environment also affect the amount of drugs a person uses. .

For the purpose of this discussion, we will focus on substances that are commonly referred to as gateway drugs:

• caffeine
• alcohol
• tobacco
• marijuana

Caffeine

Image 4.2 – Hot Coffee in a White Mug Surrounded by Coffee Beans on a Wood Table

History and Background

Caffeine is a bitter substance that occurs naturally in more than 60 plants, including coffee beans, tea leaves, kola nuts (used to flavor soft-drink colas), and cacao pods (used to make chocolate products). In addition, synthetic (man-made) caffeine is added to some medicines, foods, and drinks. For example, some pain relievers, cold medicines, and over-the-counter medicines for alertness contain synthetic caffeine, as do energy drinks, energy-boosting gums, and snacks (Medline Plus, 2021).

Caffeine’s Effects on the Body

Caffeine has many effects on your body’s metabolism. It stimulates your central nervous system, which can make you feel more awake and give you a boost of energy. Caffeine is a diuretic, meaning that it helps your body get rid of extra salt and water by urinating more.  The substance also increases the release of acid in your stomach, sometimes leading to an upset stomach or heartburn; may interfere with the absorption of calcium in the body; and increases your blood pressure.

Moderate caffeine intake is associated with positive benefits, too, if consumed through coffee. Drinking moderate amounts of coffee has been linked to lower risk of cardiovascular disease, Type 2 diabetes, and Parkinson’s disease. Although researchers have yet to determine the exact mechanisms behind some of the antioxidants present and disease-preventing effects, it is important to keep in mind that these compounds may be exerting other beneficial effects, such as acting as an anti-inflammatory. Coffee also contains small amounts of some nutrients, including potassium, niacin, and magnesium (Eat Right, n.d.).

Within one hour of eating or drinking caffeine, it reaches its peak level in your blood. You may continue to feel the effects of caffeine for four to six hours.

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Forms of Caffeine and How it is Consumed

Most people ingest caffeine from the drinks they consume.  The amounts of caffeine in different drinks can vary a great deal.

Alcohol

Image 4.3 – Collection of Several Bottles of Alcohol on a Wooden Shelf

History and Background

Alcohol comes in many forms. Beer, wine, and liquor are the standard types of alcohol consumed. The category “liquor” has hundreds of types and within those types, even more brands are available for consumers to purchase.

Ethyl alcohol, or ethanol, is an intoxicating ingredient found in beer, wine, and liquor. Alcohol is produced by the fermentation of yeast, sugars, and starches (CDC, “Alcohol and public health,” n.d.).

Some Americans have enjoyed a drink of alcohol since the first settlers arrived. But other Americans, fearing the harm alcohol would do to society and to individuals, have tried to stop others from drinking or limit who, when, and where people could consume alcohol (Bustard, 2014). Prohibition, age restrictions, and sales restrictions are all examples of regulation designed to limit others from drinking alcohol. These different views of alcoholic beverages run throughout American history and are still present today.  In early America, drinking alcohol was an accepted part of everyday life at a time when water was often contaminated and life was hard. Alcohol was not just a liquid to drink, it was also seen as medicinal by physicians (Bustard, 2014).

The table below shows how much alcohol the average drinking-age American consumed throughout history:

In the mid-1800s, various groups, many religious, started to call for a ban on alcohol. The movement gained power through the early 1900s. At 12:01 A.M. on January 17, 1920, the 18th Amendment of the U.S. Constitution went into effect to ban the manufacture, transport, and sale of alcohol and Prohibitionists rejoiced that at long last, America had become officially dry (PBS, 2021).

Image 4.4 – The U.S. is Voted Dry

However, that ban on alcohol did not last forever. Organized crime and other law breakers were still distributing alcohol. By the early 1930s, Prohibition’s modification or even repeal became politically possible. In the midst of the Great Depression, the country reversed and moved toward an acceptance of alcohol, eventually ratifying a 21st Amendment to repeal the 18th. In 1933, Americans enthusiastically celebrated the end of Prohibition. In many cities, crowds filled the streets and bars opened their doors to a rush of customers (Bustard, 2014).

Review this timeline to see alcohol consumption and trends through the years.

Alcohol’s Effects on the Body

Alcohol affects every organ in the body. Alcohol is a central nervous system (CNS) depressant that is quickly absorbed from the stomach and small intestine into the bloodstream. Alcohol is metabolized in the liver by enzymes. The liver can only metabolize a small amount of alcohol at a time, leaving the excess alcohol to circulate throughout the body. The intensity of the effect of alcohol on the body is directly related to the amount consumed (CDC Alcohol and public health, n. d.).  The more a person drinks, the more they will feel the effects.

Body size, presence of food in the body can delay the onset of effects of alcohol. Acute overdoses of alcohol cause vomiting, low blood pressure, trouble breathing, and coma. Death can occur from alcohol poisoning. Other CNS depressant drugs can increase these effects and should not be consumed together.

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Effects of Drinking Alcohol

Most people drink alcohol to “take the edge off” or “get a buzz”. These terms come from the feelings of relaxation that some people experience when drinking alcohol.

Physical Effects of Alcohol

Forms of Alcohol and How it is Consumed

A standard drink is equal to 14.0 grams (0.6 ounces) of pure alcohol. Generally, this amount of pure alcohol is found in

• 12 ounces of beer (5% alcohol content).
• 8 ounces of malt liquor (7% alcohol content).
• 5 ounces of wine (12% alcohol content).
• 1.5 ounces or a “shot” of 80-proof (40% alcohol content) distilled spirits or liquor (e.g., gin, rum, vodka, whiskey)

Image 4.5 – Alcohol by Volume (ABV) Chart

Use, Misuse, and Overuse

In America, the consumption of alcohol is regulated by many laws and regulations. One of the most important laws is the “drinking age”. The legal age to drink has changed throughout the years.

Image 4.6 – Notice: No Drinking Under 21 Sign

Minimum Legal Drinking Age (MLDA) laws specify the legal age at which an individual can purchase alcoholic beverages. The MLDA in the United States is 21 years.  However, prior to the enactment of the National Minimum Drinking Age Act of 1984, the legal age at which alcohol could be purchased varied from state to state (CDC, Minimum drinking age, n. d.).

There is also evidence that the age 21 MLDA protects drinkers from alcohol and other drug dependence, adverse birth outcomes, suicide, and homicide.

Many individuals can drink alcohol in moderation and have no problem stopping. Other individuals may find themselves engaging in misuse and overuse related to social events.

See the below definitions to understand the difference between moderate drinking, excessive alcohol use, bring drinking and getting “drunk.”

Moderate drinking: 2 drinks or less in a day for men and 1 drink or less in a day for women, when alcohol is consumed. Drinking less is better for healthier than drinking more (Dietary Guidelines for American, 2021).

Excessive alcohol use: includes binge drinking, heavy drinking, any alcohol use by people under the age of 21 minimum legal drinking age, and any alcohol use by pregnant women  (CDC, Alcohol and public health, n. d.).

Binge drinking: a pattern of alcohol consumption that brings the blood alcohol concentration (BAC) level to 0.08% or more. This pattern of drinking usually corresponds to 5 or more drinks on a single occasion for men or 4 or more drinks on a single occasion for women, generally within about 2 hours (CDC, Alcohol and public health, n. d.).

Drunk: “Getting drunk” or becoming intoxicated is the result of consuming excessive amounts of alcohol. Binge drinking typically results in acute intoxication (CDC, Alcohol and public health, n. d.).

Chronic excessive use produces physiological and psychological dependence and results in many adverse health effects. Individuals with chronic excessive use or alcoholism are at risk of alcohol withdrawal syndrome which can be a severe and life threatening condition that requires hospitalization.

Side Effects of Misuse and Overuse

Excessive drinking both in the form of heavy drinking or binge drinking, is associated with numerous health problems:

• chronic diseases such as liver cirrhosis (damage to liver cells); pancreatitis (inflammation of the pancreas); varying cancers, including liver, mouth, throat, larynx (the voice box), and esophagus; high blood pressure; and psychological disorders.
• unintentional injuries, such as falls, car crashes, drowning, burns, and firearm injuries.
• violence, such as child maltreatment, homicide, and suicide.
• harm to a developing fetus if a woman drinks while pregnant
• sudden infant death syndrome (SIDS)
• alcohol use disorders

Excessive drinking both in the form of heavy drinking or binge drinking, is associated with numerous personal problems:

• financial concerns due to the amount of money spent on alcohol
• legal concerns such as drunk driving and making bad decisions while drinking
• emotional strain on relationships
• feelings of depression

Life-Span Considerations:

Children and Teens

Studies have shown that alcohol use by adolescents and young adults increases the risk of both fatal and nonfatal injuries. Research has also shown that people who use alcohol before age 15 are six times more likely to become alcohol dependent than adults who begin drinking at age 21. Other issues include increased risky sexual behaviors, poor school performance, and increased risk of suicide and homicide (CDC, Alcohol and public health, n. d.)

Pregnancy and Lactation

Drinking alcohol at any time during pregnancy can cause serious health problems for ones baby.

When someone drinks alcohol during pregnancy, the alcohol in the blood quickly passes through the placenta and the umbilical cord to the baby. The placenta grows in the uterus (womb) and supplies the baby with food and oxygen through the umbilical cord. Drinking any amount of alcohol at any time during pregnancy can harm a baby’s developing brain and other organs. No amount of alcohol has been proven safe at any time during pregnancy (March of Dimes, n. d.).

Drinking alcohol during pregnancy increases a baby’s chances of these problems:

• premature birth
• brain damage and problems with growth and development
• birth defects, like heart defects, hearing  or vision problems
• fetal alcohol spectrum disorders (also called FASDs)
• low birthweight (also called LBW)
• miscarriage
• stillbirth

Breastfeeding women must also be aware that alcohol and other substances can be passed to their breastfed infant.

Lactating women should also follow the guidance of their healthcare provider.

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Tobacco

Image 4.7 – Picture of Cigarettes

History and Background

Tobacco use is the leading cause of preventable disease, disability, and death in the United States. Based on 2019 data, about 34 million U.S. adults smoke cigarettes. Every day, about 1,600 young people under age 18 smoke their first cigarette, and 235 begin smoking cigarettes daily. Over 16 million people live with at least one disease caused by smoking, and 58 million nonsmoking Americans are exposed to secondhand smoke (CDC, Smoking and tobacco use, n. d.). Tobacco is unique because it is a legal substance that contains nicotine which is highly addictive and highly carcinogenic (cancer causing). Tobacco is most often inhaled by cigarette, pipe, or cigar.

The tobacco industry has been a driver in American and global economies for centuries. Slave trade and slave ownership has roots in the tobacco industry. As the tobacco industry evolved into the 20th century, marketing has become a huge part of the industry.

Cigarette and smokeless tobacco companies spend billions of dollars each year to market their products. In 2019, the largest cigarette and smokeless tobacco companies spent $8.2 billion on advertising and promotional expenses in the United States alone.

For instance, the four major U.S. cigarette companies spent $7.62 billion on cigarette advertising and promotion in 2019. Additionally, the five major U.S. smokeless tobacco manufacturers spent $576.1 million on smokeless tobacco advertising and promotion in 2019. Smokeless tobacco products include dry snuff, moist snuff, plug/twist, loose-leaf chewing tobacco, snus, and dissolvable products.

The money cigarette and smokeless tobacco companies spent in 2019 on U.S. marketing amounted to

• about $22.5 million each day,
• about $25 for every person (adults and children) in the United States per year (according to 2019 population estimate of 328,239,523), and
• about $240 per year for each U.S. adult smoker (based on 34.2 million adult smokers in 2018).

Review the Center for Disease Control and Prevention’s Tobacco Marketing FactSheet

Tobacco’s Effects on the Body

Tobacco contains nicotine which is a central nervous stimulant (CNS). The effects of inhaled nicotine may last from 30 minutes to several hours. After a person uses nicotine, they may experience increased alertness, ability to focus, feelings of relaxation, and light-headedness. The individual may experience short-term enjoyment from the nicotine in tobacco.

Watch this video from TED Talks on how tobacco affects the body.

Video 4.1 – How do Cigarettes Affect the Body?

Body System and Effects

Forms of Tobacco and How it is Consumed

Tobacco comes in many forms. Click “learn more” to see the name and how it enters the body.

Use, Misuse, and Overuse

No health organizations recognize that any amount of tobacco use is safe. Thus, classifications on what is considered, safe or moderate use, do not exist.

Side Effects of Misuse and Overuse

Smoking leads to disease and disability and harms nearly every organ of the body. Smoking causes cancer, heart disease, stroke, lung diseases, diabetes, and chronic obstructive pulmonary disease (COPD), which includes emphysema and chronic bronchitis. Smoking also increases risk for tuberculosis, certain eye diseases, and problems of the immune system, including rheumatoid arthritis.

The Centers for Disease Control and Prevention have several health messaging campaigns aimed at increasing the awareness of the dangers of tobacco smoking. Tips from Former Smokers is a series of videos that highlight stories of smokers of varying ages, demographics, and ethnic groups. Watch Julia C’s story:

Video 4.2 – CDC: Tips from Former Smoker’s−Julia C.’s Wake-Up Call

Image 4.8 – Smoking Can Cause Cancer Almost Anywhere in your Body

As demonstrated in the above image, tobacco is physically harmful, but it is also carries a high financial cost.

Cigarette Sales

During 2017, about 249 billion cigarettes were sold in the United States—a 3.5% decrease from the 258 billion sold in 2016. Four companies—Philip Morris USA, Reynolds American Inc., ITG Brands, and Liggett—accounted for about 92% of U.S. cigarette sales. Imports, primarily from Canada and South Korea, accounted for approximately 8.3% of U.S. cigarette inventories in 2016 and 7.9% in 2017. By state, the average retail price of a pack of 20 cigarettes (full-priced brands), including federal and state excise taxes, ranged from $4.62 in Missouri to a high of $10.67 in New York, as of November 2017. On average, federal and state excise taxes account for 44.3% of the retail price of cigarettes (CDC, Economic trends in tobacco, n.d.)

Cost of Smoking-Related Illness

Smoking-related illness in the United States costs more than $300 billion each year, including:

• more than $225 billion for direct medical care for adults, and
• more than $156 billion in lost productivity, including $5.6 billion in lost productivity due to secondhand smoke exposure.

It can be very difficult for someone to quit smoking.

Although the benefits of quitting are greater the earlier in life that an individual quits, the United States Surgeon General report (2020) confirms that it is never too late to quit smoking. Even persons who have smoked for many years can experience substantial health and financial benefits if they stop smoking.

Image 4.9 – Cigarette Smoking Facts

Life-Span Considerations

Youth are exposed to advertising aimed specifically at their age group. Increased advertising is associated with increased e-cigarette use. Use is growing in this age group and can lead to lifetime addiction of tobacco products.

Image 4.10 – Youth Exposure to Advertising and E-Cigarette Use

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Marijuana

Image 4.11 – Picture of Marijuana

History and Background

Marijuana refers to the dried leaves, flowers, stems, and seeds from the cannabis sativa or cannabis indica plant. The plant contains the mind-altering chemical THC and other similar compounds. Extracts can also be made from the cannabis plant (NIDA, Marijuana drugFacts, 2019). Marijuana is often referred to through various street names, with weed and pot being the most common. There are multiple other slang terms that it goes by, such as “Mary Jane,” “bud,” “ganga,” “herb,” “chronic,” “grass,” “dope,” “hash,” “trees,” and “hemp”.

Marijuana is the most commonly used illegal drug in the United States, with 48.2 million users in 2019. Marijuana use may have a wide range of health effects on the body and brain.

Image 4.12 – Test Your Marijuana IQ

Go to this link to test your marijuana IQ (SAMHSA, 2021): Marijuana IQ Quiz samhsa.gov

Special Consideration: Laws Related to Marijuana Use and Distribution

State vs. Federal Perspective

At the federal level, marijuana remains classified as a Schedule I substance under the Controlled Substances Act. Schedule I substances are considered to have a high potential for dependency and no accepted medical use, making distribution of marijuana a federal offense. In October of 2009, the Obama Administration sent a memo to federal prosecutors encouraging them not to prosecute people who distribute marijuana for medical purposes legally permissible under state law.

States with medical marijuana laws generally have some form of patient registry, which may provide those using marijuana for approved medical uses with some protection against arrest for possession up to a certain amount of marijuana for personal medicinal use.

Some of the most common policy questions regarding medical marijuana include how to regulate its recommendation, dispensing, and registration of approved patients. Some states and localities without dispensary regulation are experiencing a boom in new businesses. Medical marijuana growers for dispensaries are often called “caregivers” and may be limited to growing a certain number of plants or products per patient. This issue may also be regulated on a local level, in addition to any state regulation (National Conference of State Legislatures, 2021).

Image 4.13 – State Regulated Cannabis Programs (June 2021)

Marijuana’s Effects on the Body

When a person smokes marijuana, THC quickly passes from the lungs into the bloodstream. The blood carries the chemical to the brain and other organs throughout the body. The body absorbs THC more slowly when the person eats or drinks it. In that case, a person using THC generally feels the effects after 30 minutes to 1 hour. THC acts on specific brain-cell receptors that ordinarily react to natural THC-like chemicals.

These natural chemicals play a role in normal brain development and function. Marijuana over activates parts of the brain that contain the highest number of these receptors. The activation of brain receptors causes the “high” that people feel (NIDA, Marijuana drugFacts, 2019).

THC acts on numerous areas in the brain (shown in yellow in the image below).

Image 4.14 – Areas of the Brain Affected by THC

Effects of Using Marijuana

• altered senses
• altered sense of time
• changes in mood
• impaired body movement
• difficulty with thinking and problem-solving
• impaired memory
• hallucinations (when taken in high doses)
• delusions (when taken in high doses)
• psychosis (risk is highest with regular use of high-potency marijuana)

Forms of Marijuana and How it is Consumed

People smoke marijuana in hand-rolled cigarettes (joints) or in pipes or water pipes (bongs). People also smoke it in blunts—emptied cigars that have been partly or completely refilled with marijuana.

To avoid inhaling smoke, some people use vaporizers. These devices pull the active ingredients (including THC) from the marijuana and collect their vapor in a storage unit. A person then inhales the vapor, not the smoke. Some vaporizers use a liquid marijuana extract.

People can mix marijuana in food (edibles), such as brownies, cookies, or candy, or brew it as a tea. A newly popular method of use is smoking or eating different forms of THC-rich resins which is called “dabbing” (NIDA, Marijuana drugFacts, 2019).

Image 4.15 – Marijuana Edibles

Use, Misuse, and Overuse

Marijuana use is difficult to classify. The drug may be used for medical reasons, recreation, or a combination of both. Infrequent marijuana use is unlikely to cause long-term effects.

Researchers are studying whether medical marijuana can help treat a number of conditions including:

• alzheimer’s disease
• appetite loss
• cancer
• crohn’s disease
• diseases, such as HIV/AIDS or multiple sclerosis (MS), that affect the immune system
• eating disorders such as anorexia
• epilepsy
• glaucoma
• mental-health conditions like schizophrenia and post-traumatic stress disorder (PTSD)
• muscle spasms
• nausea
• pain
• seizures
• wasting syndrome (cachexia)

A fatal overdose is unlikely, but that does not mean marijuana is harmless. The signs of using too much marijuana are similar to the typical effects of using marijuana but more severe. These signs may include extreme confusion, anxiety, paranoia, panic, fast heart rate, delusions or hallucinations, increased blood pressure, and severe nausea or vomiting.

Marijuana use can lead to the development of a substance-use disorder, a medical illness in which the person is unable to stop using even though it causes health and social problems in their life. Severe substance-use disorders are also known as addiction. Research suggests that between 9 and 30% of people who use marijuana may develop some degree of marijuana use disorder. People who begin using marijuana before age 18 are four to seven times more likely than adults to develop a marijuana-use disorder (NIDA, Marijuana drugFacts, 2019).

About 1 in 10 marijuana users will become addicted. For people who begin using before the age of 18, that number rises to 1 in 6.

Some of the signs that someone might be addicted include:

• unsuccessful efforts to quit using marijuana
• giving up important activities with friends and family in favor of using marijuana
• using marijuana even when it is known that it causes problems fulfilling everyday jobs at home, school or work

Side Effects of Misuse and Overuse

Review information from the Centers for Disease Control and Prevention on how marijuana use can impact or cause:

• addiction
• brain health
• cancer
• chronic pain
• heart health
• lung health
• mental health
• poisoning
• risk of using other drugs

Many people who use marijuana long term and are trying to quit report mild withdrawal symptoms that make quitting difficult.

Life-Span Considerations

Children and Teens

Marijuana use directly affects the parts of the brain responsible for memory, learning, attention, decision making, coordination, emotions, and reaction time. Developing brains, like those in babies, children, and teens, are especially susceptible to the adverse effects of marijuana.

Teens are also more likely to use marijuana products in other forms, such as THC vape pens. The chart below depicts use of these products.

Image 4.16 – Facts about Teenage Marijuana Vaping

Pregnancy and Lactation

Using marijuana during pregnancy may increase the baby’s risk for developmental problems. Chemicals from marijuana can be passed to the baby through breast milk. THC is stored in fat and is slowly released over time, meaning the baby could still be exposed even after you stop using marijuana.

However, data on the effects of marijuana exposure to your baby through breastfeeding are limited and conflicting. To limit potential risk to the infant, breastfeeding mothers should avoid marijuana use.

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Supplemental Resources

Substance Abuse and Medical Health Services Administration (SAMHSA). (2021, May 25). National Helplines. https://www.samhsa.gov/find-help/national-helpline

References

Burns, K. (n.d.). Roots of prohibition. Public Broadcasting Service. Retrieved July 28, 2021, from https://www.pbs.org/kenburns/prohibition/roots-of-prohibition/

Bustard, B. (2014). Spirited republic. National Archives. Retrieved July 28, 2021, from https://www.archives.gov/files/publications/prologue/2014/winter/spirited.pdf

Centers for Disease Control and Prevention. (2021, February 16). Alcohol and public health. Retrieved July 28, 2021, from https://www.cdc.gov/alcohol/faqs.htm

Centers for Disease Control and Prevention. (2015, March 26). CDC: Tips from former smokers – Julia C.’s wake-up call [Video]. YouTube. https://youtu.be/QLdEL-q-WFo

Centers for Disease Control and Prevention. (2020, September 3). Minimum legal drinking age of 21 saves lives [Fact sheet]. https://www.cdc.gov/alcohol/fact-sheets/minimum-legal-drinking-age.htm

Centers for Disease Control and Prevention. (2020, November 16). Office on Smoking and Health. Retrieved July 18, 2021, from https://www.cdc.gov/tobacco/about/osh/index.htm

Centers for Disease Control and Prevention. (2021, May 25). Tobacco sales [Fact sheet]. Retrieved July 18, 2021, from https://www.cdc.gov/tobacco/data_statistics/fact_sheets/economics/econ_facts/index.htm#sales

Klemm, S. (2020, September 29). Benefits of coffee. Retrieved July 27, 2021, from https://www.eatright.org/health/wellness/preventing-illness/benefits-of-coffee

March of Dimes. (2016, April). Alcohol during pregnancy. Retrieved July 18, 2021, from https://www.marchofdimes.org/pregnancy/alcohol-during-pregnancy.aspx

MedlinePlus (2021, July 2). Caffeine. National Library of Medicine. Retrieved July 27, 2021, from https://medlineplus.gov/caffeine.html

National Conference of State Legislatures. (2021, August 23). State medical cannabis laws. Retrieved July 18, 2021, from https://www.ncsl.org/research/health/state-medical-marijuana-laws.aspx

National Institute on Drug Abuse (NIDA). (2019, December 24). Marijuana drugFacts. U.S. Department of Health and Human Services, National Institutes of Health. Retrieved July 29, 2021, from https://nida.nih.gov/publications/drugfacts/marijuana

Rutgers Center of Alcohol & Substance Use Studies. (n.d.). History. Retrieved July 18, 2021, from  https://alcoholstudies.rutgers.edu/history/

Sudhir, K. (2018, September 13). How do cigarettes affect the body [Video]. TED. https://www.ted.com/talks/krishna_sudhir_how_do_cigarettes_affect_the_body

U.S. Department of Agriculture & U.S. Department of Health and Human Services. (2020). Dietary guidelines for Americans, 2020-2025 (9th ed.). https://www.dietaryguidelines.gov/resources/2020-2025-dietary-guidelines-online-materials

U.S. Department of Health and Human Services. (2020). Smoking cessation: A report of the Surgeon General. Retrieved July 19, 2021, from https://www.hhs.gov/sites/default/files/2020-cessation-sgr-full-report.pdf