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Marijuana: Effects, Medical Uses and Legalization

Botanical name: Cannabis sativa
Other common or street names: weed, pot, herb, bud, dope, spliff, reefer, grass, ganja, 420, chronic, Mary Jane, gangster, boom, skunk. There are over 200 street names for marijuana.

What is marijuana?

Marijuana (cannabis) is a green, brown or gray mixture of dried, shredded leaves, stems, seeds and flowers of the Cannabis sativa plant. Marijuana is used as a psychoactive, mind altering recreational drug and for certain medical ailments. The active agent that leads to the "high" is THC (delta-9-tetrahydrocannabinol). According to the National Institute on Drug Abuse (NIDA), marijuana is the most abused drug in the U.S.

Many U.S. states have legalized the use of marijuana for medical and / or recreational use, or have decriminalized its use. However, according to federal law, the possession of marijuana (cannabis) is still illegal in the U.S., except within approved research settings.

What are marijuana extracts?

Sinsemilla, hash or hashish (the resinous form) and hash oil (a sticky black liquid) are stronger forms of marijuana. Dabbing, or smoking THC-rich products, is becoming more popular. Marijuana extracts, which contain very high amounts of THC include:

How do people use marijuana?

The most common ways people use marijuana is to:

Marijuana may be smoked as a cigarette (called a joint or a nail) or in a glass pipe or a water pipe ("bong"). It may be smoked in "blunts", which are cigars that have been emptied of tobacco and refilled with marijuana, often in combination with another drug, such as crack. The “blunts” retain tobacco leaf used to wrap the cigar and therefore it combines marijuana's active ingredients with nicotine and other harmful chemicals.

Vaporizers are also popular for those who prefer not to inhale smoke. The devices concentrate the THC from the marijuana into a storage unit and the person then inhales the vapor, not the smoke. Some vaporizers use a liquid marijuana extract that can be extremely high in THC content and can be dangerous to novice users, resulting in emergency room admissions.

Some users also mix marijuana into food or use it to brew tea.

THC in marijuana is strongly absorbed by fatty tissues in various organs. Generally, traces of THC can be detected by standard urine testing methods several days or more after a smoking session. In heavy chronic users, traces can sometimes be detected for weeks.

How does marijuana get you high?

The main active chemical in marijuana is THC (delta-9-tetrahydrocannabinol), the psychoactive ingredient. The highest concentrations of THC are found in the dried flowers, or buds. When marijuana smoke is inhaled, THC rapidly passes from the lungs into the bloodstream and is carried to the brain and other organs throughout the body. When marijuana is eaten, the effects take 30 minutes to one hour.

THC from marijuana acts on specific receptors in the brain, called cannabinoid receptors, starting off a chain of cellular reactions that finally lead to the euphoria, or "high" that users experience. Activation of the endocannabinoid system leads to the release of dopamine, a neurotransmitter linked with the reward system. Certain areas in the brain, such as the hippocampus, the cerebellum, the basal ganglia and the cerebral cortex, have a higher concentration of cannabinoid receptors. These areas influence memory, concentration, pleasure, coordination, sensory and time perception.

Feeling of a relaxed state, euphoria ("high"), and an enhanced sensory perception may occur. Some people who are novice users may feel anxious, paranoid, or have a panic attack, especially if they use higher amounts or higher strengths of THC.

Marijuana's strength is correlated to the amount of THC it contains and the effects on the user depend on the strength or potency of the THC. Different strains will contain different levels of THC. In general, the THC content in marijuana has been increasing since the 1990s, when it contained less than 4% of THC. Today it may contain much higher percentages of THC and extracts can contain upwards of 50% or more of THC.

Which prescription drugs are from cannabinoids?

In the United States, the Controlled Substances Act (CSA) of 1990 classifies marijuana as a Schedule I substance, which states it has no approved medical use and a high potential for abuse. This Federal definition is highly controversial, and can limit marijuana's availability for clinical research studies. However, many US states have legalized the use of marijuana for medical use, recreational use, or have decriminalized possession.

Prescription medicines containing synthetic cannabinoids (THC) are available. Dronabinol, a pharmaceutical form of THC, and nabilone, a synthetic cannabinoid, are approved by the FDA to treat certain conditions.

Both dronabinol (Marinol and Syndros) and nabilone (Cesamet) are approved to treat patients receiving anti-cancer medicine (chemotherapy) who have nausea and vomiting, particularly patients who do not respond to other treatments.

Dronabinol (Marinol and Syndros) is also approved to treat anorexia (loss of appetite) associated with weight loss in patients with AIDS (Acquired Immune Deficiency Syndrome).

Epidiolex (cannabidiol), also called CBD, is a cannabinoid product approved by the FDA in June 2018. It is used for the treatment of patients one year of age and older with seizures associated with Lennox-Gastaut syndrome (LGS), Dravet syndrome or tuberous sclerosis complex. Epidiolex is the first FDA-approved drug that contains CBD, a purified drug substance derived from cannabis. It comes as an oral solution.

Common side effects with Epidiolex included sleepiness, diarrhea, sedation and lethargy, possible liver damage, and decreased appetite, among others. It was rescheduled from a Schedule I controlled substance to a Schedule V controlled substance in September 2018 by the DEA. However, in April 2020, the DEA fully removed the controlled drug status of Epidiolex in the US.

Sativex (nabiximols) is not currently approved for use in the US, but is available in dozens of countries outside the U.S., including Canada, the UK, Australia, New Zealand and several European countries. It is an oral sublingual (under the tongue) spray that is a 1:1 mixture of THC and cannabidiol (CBD). It is approved for use in multiple sclerosis (MS) spasticity and for chronic cancer pain in some countries.

Do prescription cannabinoids cause a positive drug test for THC?

Dronabinol (Marinol and Syndros), and Epidiolex will cause a positive urine test result for THC. Research reports have stated that Cesamet is structurally different enough from THC that it will not cause a positive urine THC metabolite test. While Sativex is not approved in the U.S., it will also cause a positive drug screen.

Before any drug testing, patients should notify their physicians and the testing lab of medicines they take, including over-the-counter (OTC) or prescription medicines (including medical marijuana), supplements, herbals or vitamins.

How many people use marijuana in the U.S?

Marijuana is by far the most commonly abused or used substance in the U.S. Close to 18% of people (49 million) age 12 and older reported using marijuana in 2020. Not surprisingly, the numbers are particularly high within younger age groups.

Marijuana is the most widely used illicit drug in the U.S., according to the 2020 National Survey on Drug Use and Health.

It was also reported that in 8th, 10th and 12th grades in 2020, daily use of marijuana were at or near the highest level recorded since 1991, according to the 2021 Monitoring the Future Survey from the National Institute on Drug Abuse (NIDA). However, in 2021, daily prevalence fell in these grades combined from 4.1% in 2020 to 3.1% in 2021 (p< .001).

What are the short-term effects from marijuana use?

Effects from marijuana use will be variable from person to person, depending upon strength and amount of marijuana used and if the user is occasionally or chronically exposed to THC. Negative side effects can be magnified in older people or younger people, novice users, and those who use high-strength THC products.

The short-term side effects of marijuana include:

Reaction time may be impaired while driving under the influence of marijuana and can be especially dangerous. This concern has become a public safety issue (Nat'l Academies of Science). NIDA research shows that drivers have slower reaction times, impaired judgment, and problems responding to signals and sounds if driving while under the influence of THC. Using marijuana and drinking alcohol together can worsen these effects.

High levels of THC can result in mental health problems. Panic attacks, paranoia and psychosis may occur acutely and be more common in psychiatric patients (Heller). For chronic users, the impact on memory and learning can last for days or weeks after its acute effects wear off, as noted by the NIDA. Marijuana, if purchased on the street, may be cut (or substituted) with substances that can lead to unknown, dangerous side effects.

What are the long-term effects from marijuana use?

Long-term side effects of marijuana can include:

There are no known reports of THC overdose leading to death.

Marijuana effects on the heart

Shortly after smoking marijuana the heart rate increases drastically and may remain elevated for up to 3 hours. This effect may be enhanced if other drugs, such as stimulants, are taken with marijuana.

Harvard Health also reports that the risk of a heart attack is several times higher in the hour after smoking marijuana, and this should be a red flag for anyone with a history of heart disease. The risk of stroke may be increased, as well.

Marijuana effects on the lungs

Studies have shown that marijuana smoke contains cancer-causing hydrocarbons and is an irritant to the lungs. Marijuana users tend to inhale more deeply and hold their breath longer than tobacco smokers do, which further increases lung exposure to the smoke.

People who smoke marijuana often have the same respiratory problems as cigarette smokers. These individuals may have daily cough and phlegm, symptoms of chronic bronchitis, shortness of breath, chest tightness, wheezing and more frequent chest colds. They are also at greater risk of getting lung infections like pneumonia, as reported by the NIDA. Many people who smoke marijuana also smoke cigarettes.

Research from the National Academies of Sciences has not found a strong association between marijuana use and development of lung cancer. However, a systematic review by Martinasek and colleagues indicates that there is a risk of lung cancer from inhalational marijuana, as well as an association between smoking marijuana and spontaneous pneumothorax, emphysema, or chronic obstructive pulmonary disease (COPD). In the review, 8 of the 12 studies indicated an increased risk of lung cancer from cannabis use or cases indicating lung cancer occurrence.

Marijuana effects on mental health

Marijuana also may affect mental health. Studies show that use may increase the risk of developing psychosis (a severe mental disorder in which there is a loss of contact with reality) including false ideas about what is happening (delusions) and seeing or hearing things that aren’t there (hallucinations), particularly if you carry a genetic vulnerability to the disease. Teens may be at a high risk for these mental health problems. (NIDA)

Also, rates of marijuana use are often higher in people with symptoms of depression or anxiety, as reported by the NIDA.

Marijuana effects during pregnancy and breastfeeding

Marijuana is also the most common illicit drug used during pregnancy, in roughly 2% to 5% of women.

According to a report published by the American College of Obstetricians and Gynecologists (ACOG) entitled Marijuana Use During Pregnancy and Lactation, 34% to 60% of marijuana users continue use during pregnancy, with many women believing that use is relatively safe. These numbers could rise as more states continue to legalize marijuana for medicinal or recreational purposes. Due to possible side effects of marijuana on the fetus, ACOG recommends that marijuana should be avoided during pregnancy.

Human fetuses exhibit the cannabinoid receptor type 1 in the nervous system as early as 14 weeks of gestation, and animal studies suggest cannabinoid exposure may lead to abnormal brain development. As reported by de Moraes Barro and colleagues, babies born to adolescents who used marijuana during pregnancy have shown adverse neurological behavior effects of the newborns in the first 24 to 78 hours after delivery.

Most reports do not show an association between marijuana use and preterm birth. However, as noted by ACOG, studies have suggested the use of marijuana with tobacco may increase the risk for preterm delivery. In addition, research demonstrates that babies born to mothers who used marijuana during pregnancy at least once per week (or more) were smaller than those born to mothers who used the drug less frequently.

Studies on school performance have shown differing results: in middle class children age 5 to 12 years, no specific cognitive effects were seen; however, in lower socioeconomic, primarily urban groups, poorer reading and spelling scores and lower teacher-perceived school performance was observed, per ACOG.

THC is excreted in breast milk, as noted by Davies. ACOG recommends that marijuana use be discontinued during breastfeeding. The scientific data are not strong enough to determine the risk to the nursing infant.

Addictive potential of marijuana

A drug is addicting if it causes compulsive, uncontrollable drug craving, drug seeking, and use, even in the face of negative health and social consequences. Long-term abuse of marijuana may lead to dependence or addiction, known as marijuana use disorder, in some people.

Research suggests that roughly 9% of users become addicted to marijuana, with higher rates if the user starts at a young age (17%) and in those who use marijuana daily (25% to 50%). While not everyone who uses marijuana becomes addicted, when a user begins to seek out and take the drug compulsively, that person is said to be dependent or addicted to the drug. Some heavy users develop a tolerance to marijuana, meaning that the user needs larger amounts to get the same desired results that he or she used to get from smaller amounts, as noted by the NIDA.

Long-term users who try to quit could experience withdrawal symptoms such as sleeplessness, irritability, anxiety, decreased appetite and drug craving. Withdrawal symptoms usually begin about a day after the person stops using marijuana, peaks in 2 to 3 days and may take about 1 to 2 weeks to subside. McKenna reports that marijuana addiction is difficult to treat in the clinic. Patients can have a lengthy withdrawal and symptoms that can continue for months after stopping marijuana use.

One study from McKenna and colleagues reported on the addicting potential of marijuana, noting that "it is an erroneous belief widely held by the general public, and among many physicians, that marijuana is not addicting." However, not all people will become addicted to marijuana and the effects can be psychological in some patients.

Withdrawal symptoms can occur upon abrupt cessation of the drug, including:

Cannabis hyperemesis syndrome

Ironically, while cannabinoids and cannabis are often used to treat severe nausea and vomiting, long-term use of marijuana can rarely cause cycles of severe nausea, vomiting and dehydration in certain people. These episodes, called cannabis hyperemesis syndrome, may require emergency treatment. Cannabis hyperemesis syndrome typically leads to persistent vomiting without breaks.

To determine if the severe nausea and vomiting is due to marijuana use, most people will need to stop use of marijuana for a week or two to determine if their symptoms improve. Cannabis hyperemesis syndrome can be mistaken for cyclic vomiting syndrome, which is characterized by episodes of severe vomiting that have no apparent cause.

Which states allow medical marijuana?

Multiple U.S. states, the District of Columbia, Puerto Rico, US Virgin Islands and Guam now legally allow marijuana for personal medical use. Rules surrounding the use and possession of medical marijuana vary by state.

The first state in the union to legalize the medical use of marijuana was California in 1996 with Proposition 215.

States / territories that allow medical marijuana, to date, include: Alabama, Alaska, Arizona, Arkansas, California, Colorado, Connecticut, Delaware, Florida, Georgia, Hawaii, Illinois, Iowa, Louisiana, Maine, Maryland, Massachusetts, Michigan, Minnesota, Mississippi, Missouri, Montana, Nevada, New Hampshire, New Jersey, New Mexico, New York, North Dakota, Ohio, Oklahoma, Oregon, Pennsylvania, Rhode Island, South Dakota, Utah, Vermont, Virginia, Washington, and West Virginia, plus the District of Columbia, Puerto Rico, the US Virgin Islands, Guam and the commonwealth Mariana Islands. Note: some states may have passed laws but still may be in the process of finalizing procedures and rules surrounding distribution.

Marijuana has been used as a therapeutic and medicinal agent for centuries, dating back to the 27th century BC. Today, it is still used for medicinal purposes, although restrictive laws surrounding its use now exist. Medical marijuana is available in many different forms from dispensaries: as an oil, pill, vaporized liquid, nasal spray, edibles and as the dried plant product.

Legal Status of Medical Marijuana

Medical marijuana in the U.S. is controlled at the state level. It is important to recognize that state medical and recreational marijuana laws do not change the fact that using marijuana continues to be an offense under U.S. federal law. Per federal law, cannabis (marijuana, hashish) is a schedule I drug.

Use of medical marijuana outside of the state laws for illegal use or trafficking would not be tolerated by state or federal government.

In general, in order to qualify for legal medical marijuana, patients must: have a diagnosed condition that is on their state’s list of qualifying medical marijuana conditions and receive a medical recommendation from their doctor. The patient can then obtain a medical marijuana card, or qualification, to purchase medical marijuana and associated products from dispensaries.


Although the conditions vary from state-to-state, medical conditions for which patients might use medical marijuana include:

Based on a comprehensive research report from The National Academies of Sciences, Engineering, and Medicine, there is conclusive or substantial evidence that cannabis or cannabinoids are effective for the treatment of:

There is moderate evidence that cannabis or cannabinoids are effective for:

Which states allow recreational use of marijuana?

Rules surrounding recreational use of marijuana vary by state or territory. Check the laws in each area, as differences exist for quantity allowed, plant growing, and retail sales, among other factors.

To date, states or territories where recreational use of marijuana is legal include:

Note: some states may have passed laws but still may be in the process of finalizing procedures and rules surrounding distribution and retail sales.

It is important to note that the federal government still considers marijuana an illegal drug and that the illegal distribution and sale of marijuana is a federal crime. Under the Controlled Substances Act (CSA), marijuana is still considered a Schedule 1 drug.

Cities, municipalities, employers, landlords, and universities may have special policies about the use of marijuana. Use within any federal land, national park or monument is still illegal. Be sure to check all rules before use, especially in areas that may be under federal law.

Does marijuana use making driving dangerous?

Smoking marijuana can make driving dangerous; do not mix the two. The cerebellum is the section of the brain that controls balance and coordination. When THC affects the cerebellum’s function, drivers may have slower reaction times, impaired judgment, and problems responding to signals and sounds if driving while under the influence (DUI) of THC.

In all states, including states that allow recreational marijuana, driving under the influence of marijuana is illegal.

The American Academy of Pediatrics (AAP) released a report urging doctors to protect children from the harms of marijuana as the U.S. becomes increasingly tolerant to the drug. The brain is not fully developed until around 25 years of age. Experts note that marijuana use in the young can lead to abnormal brain development.

Frequent use of high-potency THC over extended periods of time suggests that there can be negative effects on learning, memory, attention and problem-solving ability, as reported in Pediatrics. The AAP suggests that doctors urge parents not to use marijuana around children. Other concerns with children include the potential of exposing them to secondhand smoke and accidental poisoning with edibles such as brownies or candy.


See also


Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.