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Public Health - Seattle & King County

Marijuana and health

Is marijuana a safe drug?

Although marijuana use by adults has been made legal in Washington State, that does not mean it is without health risks. The safety of marijuana has not been established. Just like tobacco and alcohol, it has been associated with health and social problems. It is difficult to predict how marijuana will impact any individual because marijuana has not been studied as much as other drugs. Like alcohol – there are individuals who may use marijuana infrequently while others will become regular users and possibly dependent. Read more about marijuana and health in these articles published in the New England Journal of Medicine, the Journal of the American Medical Association and at the National Institute of Drug Abuse website.

Cannabinoids, the active ingredient in marijuana, affect areas throughout the body, but they mostly affect the central nervous system (brain and spinal cord). The main cannabinoid chemical in marijuana that causes intoxication is tetrahydrocannabinol (THC). Another cannabinoid of medical interest is cannabidiol (CBD), which does not cause intoxication.

Marijuana, like all drugs, has potential risks. Regular smoking of marijuana is associated with breathing problems such as cough and increased risk of lung infections. It can also be addicting and can cause problems with thinking, memory and coordination, anxiety, depression, and other behavioral effects that interfere with work, school, and relationships. It causes an increase in heart rate, which may increase the chance of heart attack in people who are already at risk. Marijuana can also cause problems with brain development in adolescents through 25 years of age that can be long-lasting, including possible decline in IQ among adolescent marijuana users.

More common effects of marijuana can include dizziness, dry mouth, disorientation, euphoria, confusion, sedation, nausea, vomiting, muscle spasms and increased appetite.

How marijuana affects health is determined by how it's consumed. Marijuana is most commonly smoked, such as from pipes, bongs, paper-wrapped joints, blunts and other items including devices that heat or vaporize marijuana. It can also be consumed through foods and beverages, such as brownies or tea.

Does marijuana cause lung disease or cancer?

Smoking marijuana can damage the lungs resulting in chronic cough, phlegm production, wheezing, and bronchitis. Smoke from marijuana combustion has been shown to contain many of the same toxins, irritants and carcinogens as tobacco smoke. Marijuana smokers also tend to inhale more deeply and hold their breath longer than cigarette smokers, which leads to greater exposure. Long-term marijuana smoking is not known to be linked to an increased risk for lung cancer.

Secondhand marijuana smoke contains many of the same toxins and carcinogens found in directly inhaled marijuana smoke, in similar amounts if not more. While there is no data on the health consequences of breathing secondhand marijuana smoke, there is concern that it could cause harmful health effects, especially among vulnerable children in the home. Additional research on the health effects of secondhand marijuana smoke is needed.

Smoking marijuana also hurts the lung's first line of defense against infection by killing cells that help remove dust and germs as well as causing more mucus to be formed.

Marijuana smoking also poses a threat to those with weakened immune systems. Aspergillus is a mold that can cause lung disorders and can grow on marijuana, which if then smoked exposes the lungs to this fungus. However, it rarely causes problems in people with healthy immune systems. Marijuana from licensed and regulated retailers in Washington State is inspected to reduce the risk for contamination.

Learn more from the American Lung Association on Marijuana and Lung Health.

Is consuming marijuana through a vaporizer safer than smoking marijuana?

Vaporizers are machines that heat the marijuana to release its active ingredients in a mist without smoke. This may reduce respiratory complaints and any specific medical risks associated with inhaling smoke. The potential adverse neurologic, cardiac and behavioral effects of marijuana would still be present when smoked through a vaporizer.

Is there a difference between eating and smoking marijuana?

Yes. People should be careful when eating marijuana because of delayed effects. Eating marijuana rather than smoking it avoids the potential health impacts from smoke on the throat and lungs. However, effects from eating marijuana can be delayed. Typically, it takes 30–60 minutes to feel effects from eating marijuana, peaking at approximately 2–3 hours after eating. The effects from eating marijuana last longer than some users prefer. Although the effects are similar to smoked marijuana, the delayed onset of feeling high may make it difficult to control how much one consumes, increasing the risk of taking more than desired. The potential adverse neurologic, cardiac and behavioral effects of marijuana would still be present when it is eaten.

Can teenagers use recreational marijuana?

No. Anyone under the age of 21 cannot purchase or use recreational marijuana. Studies suggest that the younger a person starts using marijuana regularly, the more likely they are to become addicted. The teenage brain is still developing, and some studies suggest regular use can cause problems with brain development, memory, learning and attention, school completion, and behavioral problems. Some studies have shown that adolescents who use marijuana regularly are at higher risk of developing depression or schizophrenia. Read more about Adolescents and Marijuana from the University of Washington's Alcohol & Drug Abuse Institute (ADAI).

Public Health is very concerned about preventing youth access to marijuana. King County has proposed to the Liquor Control Board strong advertising, labeling and packaging rules similar to tobacco and alcohol. King County has also requested strong health warnings in educational materials that will be distributed, for these warnings to be posted at the point of sale, and a ban on products that infuse marijuana and alcohol or marijuana and tobacco due to their potential appeal to youth.

Should pregnant or breastfeeding women use marijuana?

No. Just like with alcohol and cigarettes, there is likely no safe amount of marijuana use in pregnancy. If a mother is using marijuana she can pass the active ingredient in marijuana, called THC, to the baby through her placenta before the baby is born and through her breast milk when breast feeding. There are not enough good quality studies to know with certainty how marijuana use affects the developing fetus and breastfeeding baby, but there is cause for concern. Marijuana may cause problems with the development of the baby's brain and nervous system. There are also concerns regarding the effects of marijuana smoke on the mother and baby. Pregnant women or women contemplating pregnancy should discontinue use of marijuana for medicinal purposes in favor of an alternative therapy for which there are better pregnancy-specific safety data.

Additional information about marijuana, pregnancy and breastfeeding is available at ADAI and the American College of Obstetrics and Gynecology.

Should I drive after using marijuana?

No. People under the influence of marijuana should not drive or operate complex machinery. Like alcohol, marijuana can interfere with coordination, alertness, and slow a person's response time, putting them and others around them at risk of harm. Read more about Marijuana and Driving at ADAI.

Is marijuana safe for use while taking prescribed medications?

Not always. As with alcohol, marijuana should not be used by people on any medication that decreases one's ability to safely drive or operate complex machinery. Drugs that should not be combined with marijuana include opiate medications and benzodiazepines. People taking medications for alcohol or drug dependency, depression, anxiety, panic or thought disorders should also avoid using marijuana. People taking other prescription medications should talk with their health care provider about the risk of other interactions.

Read more about Marijuana and Prescribed Medications at ADAI.

Is synthetic marijuana safe?

No. Sometimes referred to as "spice," synthetic marijuana can cause agitation, nausea, vomiting, tachycardia (rapid heartbeat), elevated blood pressure, tremor, seizures, hallucinations, paranoid behavior and coma. It does not contain any of the ingredients found in actual marijuana. Read more about synthetic marijuana's link to hospital emergency visits at the U.S. Substance Abuse and Mental Health Services Administration.

How often do people become addicted?

It is estimated that about one in ten people who use marijuana will become dependent on the drug. The more frequently a person uses the drug, the more likely they are to become dependent. It is not known if marijuana use increases the risk for use of other drugs (i.e. if marijuana is a "gateway drug").

Do people using marijuana regularly experience withdrawal?

Yes. Marijuana affects the brain's "reward center" in the same way as many other drugs. Some studies have shown that regular marijuana users experience withdrawal symptoms for several weeks after they stop using. Withdrawal symptoms can include anxiety, restlessness, decreased appetite, irritability and trouble sleeping, including having strange dreams.

Is marijuana medicine?

Although many people use marijuana to treat conditions including pain and nausea caused by HIV/AIDS, cancer, and other conditions, the scientific evidence to date is not sufficient for the marijuana plant to gain FDA approval.

Two synthetic cannabinoids, dronabinol and nabilone, are available in pill form. These drugs are FDA approved and available by prescription. They are used in some patients to treat nausea and vomiting due to chemotherapy. Dronabinol is also used to treat loss of appetite and weight loss in patients with HIV/AIDS or cancer.

What are the effects of marijuana consumption?

Effects may include:

  • a mildly euphoric, relaxing intoxication or "high;"
  • impaired coordination; dizziness
  • difficulty with thinking, problem solving, learning and memory;
  • distorted perception; anxiety, panic or paranoia;
  • decreased motivation;
  • increase in heart rate; lowering of blood pressure; and
  • appetite stimulation; dry mouth

Very rarely marijuana use may lead to acute psychosis involving delusions and hallucinations. Read more about the therapeutic potential of cannabis (PDF, The Lancet)

Are there any data on local marijuana smoking?

Youth marijuana use data for King County is available as part of the Community Health Indicators.

Download the Youth Adult Health Survey on Young adults and marijuana: Use, sources, and perception of risk (March 2015) from the University of Washington.

Where can I go for marijuana treatment help?

Call the Washington Recovery Help Line-24 Hours Help for Substance Abuse, Mental Health and Problem Gambling 1-866-789-1511.

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