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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 hemp plant Cannabis sativa. Marijuana is used as a psychoactive (i.e. mind altering) recreational drug, for certain medical ailments and for religious and spiritual purposes. Sinsemilla, hash/hashish (resinous form) and hash oil (sticky black liquid) are stronger forms of marijuana.

According to the National Institute on Drug Abuse (NIDA), marijuana is the most abused drug in the US. Many states in the US have now legalized marijuana for medical and/or recreational use. However, according to federal law, the possession of marijuana (cannabis) is still illegal in the US, except within approved research settings.

How does marijuana work?

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. THC from the 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. Feeling of a relaxed state, euphoria, and an enhanced sensory perception may occur. With higher THC levels in those who are not used to the effects, some people may feel anxious, paranoid, or have a panic attack. 

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.1

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 1970s, when it contained roughly 10% THC. In 2015, as reported by Live Science, researchers from the American Chemical Society found levels of THC at roughly 30%.

There are many other chemicals found in marijuana, many of which may adversely affect health. Marijuana contains over 60 different cannabinoid compounds, and overall 400 different compounds have been identified in marijuana, including THC, cannabidiol (CBD), cannabinol, and β-caryophyllene, as noted by the National Institute of Drug Abuse (NIDA).

How is marijuana used?

Marijuana may be smoked as a cigarette (called a joint or a nail) or in a pipe or 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.

Some users also mix marijuana into food or use it to brew tea. In states that have now legalized sale of marijuana for recreational use, the marketing of edible products, such as cookies, brownies, chocolates, and gummies are popular for those who prefer not to smoke the product.

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.

Approved and investigational products

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

  • Marinol, generics (dronabinol capsules) - Classified as Schedule III
  • Syndros (dronabinol liquid) - Classified as Schedule II
  • Cesamet (nabilone capsules) - Classified as Schedule II

Syndros is a liquid form of dronabinol. Both dronabinol and nabilone 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).

  • Sativex (nabiximols)

Sativex (nabiximols) is not currently approved for use in the US, but is available in dozens of countries outside the US, including Canada, the UK, Spain, Germany, Denmark, the Czech Republic, Sweden, and New Zealand.

  • Sativex, an oral sublingual spray, is approved for use in multiple sclerosis (MS) spasticity, and for chronic cancer pain in some countries.
  • Sativex is composed of standardized extracts of THC and cannabidiol and is available as an oral mucosal spray formulation.
  • Studies (Lakhan) report that THC and cannabidiol (CBD) provide therapeutic benefit for Multiple Sclerosis (MS) spasticity (muscle stiffness / spasm) symptoms. 

GW Pharmaceuticals and Otsuka Pharmaceuticals announced results of three US Phase 3 trials in 2015 for the use of Sativex for the treatment of pain in patients with advanced cancer who experience inadequate analgesia during optimized chronic opioid therapy. According to the study results, Sativex did not meet the primary endpoint of demonstrating a statistically significant difference from placebo for pain control.

Epidiolex (cannabidiol), also called CBD, is a cannabinoid product approved in June 2018. It is used for the treatment of patients one year 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.

Extent of marijuana use

Marijuana is by far the most commonly abused or used substance in the U.S. Not surprisingly, the numbers are particularly high within younger age groups.

In the 2019 Monitoring the Future Survey from the National Institute on Drug Abuse (NIDA), 35.7% of 12th graders reported marijuana use in the past year. This compares to 28.8% of 10th graders and 11.8% of 8th graders.

  • In 2019, it was found that vaping of marijuana on the rise among teens.
  • However, the survey continues to find declines in prescription opioid misuse, tobacco cigarettes, and alcohol

Marijuana is reported as the most widely used illicit drug in the US, according to the 2018 National Survey on Drug Use and Health.

  • In the past survey year, over 43 million people age 12 and older reported using marijuana.
  • In the same survey, past year marijuana use among adolescents aged 12 to 17 years was over 3 million in 2018.
  • Overall, marijuana use was highest amongst the age group 18 to 25 years of age at 34%.

Marijuana side effects

Side effects of 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. Side effects can be magnified in older people.

The short-term effects of marijuana or cannabinoid use include:

  • increased heart rate
  • low blood pressure, orthostatic hypotension
  • muscle relaxation
  • slowed digestion
  • dizziness
  • distorted perception (sights, sounds, time, touch)
  • difficulty in thinking, memory, and problem solving
  • loss of coordination and motor skills
  • agitation, anxiety, confusion, panic, paranoia
  • increased appetite
  • dry mouth, dry eyes

Reaction time may be impaired while driving. 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.

Panic attacks, paranoia and psychosis may occur acutely and be more common in psychiatric patients, a reported by 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.

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 after they have stopped using marijuana.

Long-term abuse of marijuana may lead to dependence in some people. One study (McKenna) 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:

  • anxiety
  • agitation
  • tremulousness
  • elevation of vital signs
  • insomnia
  • irritability

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. Also, rates of marijuana use are often higher in people with symptoms of depression or anxiety, as reported by the NIDA. There have been no 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 are taken with marijuana.

  • One study (Mittleman) has suggested that the risk of heart attack may increase by up to 4.8-fold in the first hour after smoking marijuana. The effect may be due to the increased heart rate and altered heart rhythms.
  • The risk of heart attack may be greater in those with specific risk factors such as patients with high blood pressure, heart arrhythmia, or other cardiac disease.

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 carcinogenic smoke. 

  • After smoking marijuana, the bronchial passage relaxes and becomes enlarged. Marijuana smoke contains many of the same cancer-causing chemicals found in cigarette smoke, often in greater quantities (Mehmedic).
  • Both types of smoke contain cancer-causing nitrosamines, polycyclic aromatic hydrocarbons, vinyl chlorides, and phenol (Martinasek).

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.

A systematic review (Martinasek) of the respiratory effects of marijuana indicates that there is a risk of lung cancer from inhalational marijuana as well as an association between inhalational marijuana and spontaneous pneumothorax, emphysema, or COPD. In the review, eight of the 12 studies indicated an increased risk of lung cancer from cannabis use or cases indicating lung cancer occurrence.

Drug interactions with marijuana

  • Combining marijuana with other CNS depressant drugs that also cause drowsiness or sedation (such as alcohol, barbiturates, sedating antihistamines, anti-anxiety medications, opiate pain killers, etc) can magnify the drowsiness.
  • A study (Hartman) shows that low doses of alcohol can significantly elevate the concentrations of THC in the blood.
  • Marijuana use can raise the heart rate (tachycardia) and may be dangerous if used with other drugs that may also increase the heart rate. People with cardiovascular disease should avoid marijuana use.
  • The cannabinoids in marijuana (THC, cannabidiol) can affect liver enzymes and may alter the blood levels and effects of medications. 
  • Drug interactions are often unpredictable or undocumented with marijuana and extreme caution should be exercised.
  • DO NOT drive if you are under the influence of marijuana, alcohol or any sedating drug. This is illegal in all U.S. states, even where recreational marijuana use is legal.

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.

  • Any drug of abuse can affect a mother's health.
  • It can be difficult to determine the effects of marijuana on a baby’s health because women who use marijuana often use other substances, such as alcohol, nicotine, or drugs of abuse.
  • THC appears to cross the placenta (Davies).

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 (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.

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 (25-50%). 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.

Which states / territories 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 include: Alabama, Alaska, Arizona, Arkansas, California, Colorado, Connecticut, Delaware, Florida, Hawaii, Illinois, Iowa, Louisiana, Maine, Maryland, Massachusetts, Michigan, Minnesota, 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 and Guam. 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:

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. States or territories where recreational use of marijuana is legal include:

  • Alaska
  • Arizona
  • California
  • Colorado
  • Guam (territory)
  • Illinois
  • Maine
  • Massachusetts
  • Michigan
  • Montana
  • Nevada
  • New Jersey
  • New Mexico
  • New York
  • Oregon
  • South Dakota
  • Vermont 
  • Virginia
  • Washington (State)
  • Washington, D.C. 

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

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. 

Marijuana dangers: driving, use in children

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.

  • However, because THC metabolites can remain in the blood for up to one month (or possibly longer), the DUI charge is usually based subjective measures.
  • The evaluation will take into account driving patterns, one’s physical symptoms and appearance, a field sobriety test, and possibly a blood test for THC.
  • States differ on the penalties, although an arrest and court date will most likely be involved if the officer deems the person impaired.
  • First offenses rarely involve long jail time, but may involve probation, community service, a suspended license, fines and fees, and DUI school.

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.

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