Health Effects

Marijuana: How Can It Affect Your Health?

Marijuana is the most commonly used illegal drug in the United States, with 37.6 million users in the past year,1 and marijuana use may have a wide range of health effects on the body and brain. Click on the sections below to learn more about how marijuana use can affect your health.

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. 1-3

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.4

People who are addicted to marijuana may also be at a higher risk of other negative consequences of using the drug, such as problems with attention, memory, and learning. Some people who are addicted need to smoke more and more marijuana to get the same high. It is also important to be aware that the amount of tetrahydrocannabinol (THC) in marijuana (i.e., marijuana potency or strength) has increased over the past few decades. The higher the THC content, the stronger the effects on the brain. In addition, some methods of using marijuana (e.g., dabbing, edibles) may deliver very high levels of THC to the user.5 Researchers do not yet know the full extent of the consequences when the body and brain (especially the developing brain) are exposed to high concentrations of THC or how recent increases in potency affect the risk of someone becoming addicted. 5

References

  1. Lopez-Quintero, C, et al. (2011). Probability and predictors of transition from first use to dependence on nicotine, alcohol, cannabis, and cocaine: results of the National Epidemiologic Survey on Alcohol and Related Conditions (NESARC). Drug Alcohol Depend. 115(1-2): p. 120-30.
  2. Hall, W, Degenhardt L. (2009). Adverse health effects of non-medical cannabis use. Lancet. 374(9698): p. 1383-91.
  3. Budney, AJ, Sargent JD, and Lee, DC. (2015). Vaping cannabis (marijuana): parallel concerns to e-cigs? Addiction. 110(11): p. 1699-704.
  4. American Psychiatric Association. (2013). Diagnostic and statistical manual of mental disorders (5th ed.). Arlington, VA: American Psychiatric Publishing.
  5. National Institute on Drug Abuse. Is marijuana addictive?External (2017) Rockville, MD: National Institutes of Health, National Institute on Drug Abuse.

Marijuana use directly affects the brain — specifically the parts of the brain responsible for memory, learning, attention, decision making, coordination, emotions, and reaction time.1

What are the short-term effects of marijuana on the brain?

Heavy users of marijuana can have short-term problems with attention, memory, and learning, which can affect relationships and mood.

What are the long-term effects of marijuana on the brain?

Marijuana also affects brain development. When marijuana users begin using as teenagers, the drug may reduce attention, memory, and learning functions and affect how the brain builds connections between the areas necessary for these functions.

Marijuana’s effects on these abilities may last a long time or even be permanent. This means that someone who uses marijuana may not do as well in school and may have trouble remembering things. 1-3

The impact depends on many factors and is different for each person. It also depends on the amount of tetrahydrocannabinol (THC) in marijuana (i.e., marijuana potency or strength), how often it is used, the age of first use, and whether other substances (e.g., tobacco and alcohol) are used at the same time.

Marijuana and the developing brain

Developing brains, like those in babies, children, and teenagers are especially susceptible to the hurtful effects of marijuana. Although scientists are still learning about these effects of marijuana on the developing brain, studies show that marijuana use by mothers during pregnancy may be linked to problems with attention, memory, problem-solving skills, and behavior problems in their children. 3-7

References

  1. Batalla A, Bhattacharyya S, Yücel M, et al. (2013). Structural and functional imaging studies in chronic cannabis users: a systematic review of adolescent and adult findings. PloS One. 8(2):e55821. doi:10.1371/journal.pone.0055821.
  2. Filbey, FM, et al., Long-term effects of marijuana use on the brain. (2014) Proc Natl Acad Sci USA. 111(47): p. 16913-8.
  3. Goldschmidt, L, et al. (2002). Richardson, Effects of prenatal marijuana exposure on child behavior problems at age 10. Neurotoxicol Teratol. 22(3): p. 325-36.
  4. Fried, PA, Watkinson, B, and Gray, R. Differential effects on cognitive functioning in 9- to 12-year olds prenatally exposed to cigarettes and marihuana. Neurotoxicol Teratol, 1998. 20(3): p. 293-306.
  5. Leech, SL, et al., (1999). Prenatal substance exposure: effects on attention and impulsivity of 6-year-olds. Neurotoxicol Teratol. 21(2): p. 109-18.
  6. Goldschmidt, L, et al., (2008) Prenatal marijuana exposure and intelligence test performance at age 6. J Am Acad Child Adolesc Psychiatry. 47(3): p. 254-63.
  7. El Marroun, H, et al., (2011). Intrauterine cannabis exposure leads to more aggressive behavior and attention problems in 18-month-old girls. Drug Alcohol Depend. 118(2-3): p. 470-4.

Marijuana and cannabinoids (the active chemicals in marijuana that cause drug-like effects throughout the body, including the central nervous system and the immune system). The main active cannabinoid in marijuana is delta-9-THC. Another active cannabinoid is cannabidiol (CBD), which may relieve pain and lower inflammation without causing the “high” of delta-9-THC. Although marijuana and cannabinoids have been studied with respect to managing side effects of cancer and cancer therapies, there are no ongoing clinical trials of marijuana or cannabinoids in treating cancer in people.9 Studies so far have not shown that cannabinoids help control or cure the disease.2 And like many other drugs, marijuana can cause side effects and complications.

Relying on marijuana alone as treatment or for managing side effects while avoiding or delaying conventional medical care for cancer may have serious health consequences.2

How can marijuana affect symptoms of cancer?

Studies of man-made forms of the chemicals found in the marijuana plant can be helpful in treating nausea and vomiting from cancer chemotherapy.1 Studies have found that marijuana can be helpful in treating neuropathic pain (pain caused by damaged nerves).1

At this time, there is not enough evidence to recommend that patients inhale or ingest marijuana as a treatment for cancer-related symptoms or side effects of cancer therapy.

Is there a link between marijuana and cancer?

Smoked marijuana delivers THC and other cannabinoids to the body, but it also delivers harmful substances to users and those close by, including many of the same substances found in tobacco smoke, which are harmful to the lungs and cardiovascular system.3

Researchers have found limited evidence of an association between current, frequent, or chronic marijuana smoking and testicular cancer (non-seminoma-type).4

Because marijuana plants come in different strains with different levels of active chemicals, it can make each user’s experience very hard to predict. More research is needed to understand the full impact of marijuana use on cancer.

References

  1. National Academies of Sciences E, and Medicine. (2017). The health effects of cannabis and cannabinoids: Current state of evidence and recommendations for researchExternal. Washington, D.C.
  2. National Cancer Institute. (2017). Cannabis and Cannabinoids (PDQ®)–Patient VersionExternal. Rockville, MD: National Institutes of Health, National Cancer Institute.
  3. U.S. Department of Health and Human Services. (2014). The Health Consequences of Smoking: 50 Years of Progress. A Report of the Surgeon General Cdc-pdf[PDF – 36MB]External. Atlanta, GA: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion, Office on Smoking and Health.
  4. Gurney, J, et al. (2015). Cannabis exposure and risk of testicular cancer: a systematic review and meta-analysis. BMC Cancer. 15: p. 897.

Even though pain management is one of the most common reasons people use medical marijuana in the U.S., there is limited evidence that marijuana works to treat most types of chronic pain.

A few studies have found that marijuana can be helpful in treating neuropathic pain (pain caused by damaged nerves). 1 However, more research is needed to know if marijuana is any better or any worse than other options for managing chronic pain.

References

  1. National Academies of Sciences E, and Medicine. (2017). The health effects of cannabis and cannabinoids: Current state of evidence and recommendations for researchExternal. Washington, D.C.

Using marijuana makes the heart beat faster.1 It could also lead to increased risk of stroke and heart disease. 2-6 However, most of the scientific studies linking marijuana to heart attacks and strokes are based on reports from people who smoked it. Smoked marijuana delivers THC and other cannabinoids to the body, but it also delivers harmful substances to users and those close by, including many of the same substances found in tobacco smoke, which are harmful to the lungs and cardiovascular system. 3 So it’s hard to separate the effects of the compounds in marijuana on the cardiovascular system from the hazards posed by the irritants and other chemicals contained in the smoke. More research is needed to understand the full impact of marijuana use on the circulatory system to determine if marijuana use leads to higher risk of death from these causes.

References

  1. Sidney, S. (2002) Cardiovascular consequences of marijuana use. J Clin Pharmacol. 42(11 Suppl): p. 64S-70S.
  2. Wolff, V, et al. (2013). Cannabis-related stroke: myth or reality? Stroke. 44(2): p. 558-63.
  3. Wolff, V, et al. (2015). Characteristics and Prognosis of Ischemic Stroke in Young Cannabis Users Compared With Non-Cannabis Users. J Am Coll Cardiol. 66(18): p. 2052-3.
  4. Franz, CA and Frishman, WH. (2016) Marijuana Use and Cardiovascular Disease. Cardiol Rev. 24(4): p. 158-62.
  5. Rumalla, K, Reddy, AY, and Mittal, MK. (2016). Recreational marijuana use and acute ischemic stroke: A population-based analysis of hospitalized patients in the United States. J Neurol Sci. 364: p. 191-6.
  6. Rumalla, K, Reddy, AY, and Mittal, MK. (2016). Association of Recreational Marijuana Use with Aneurysmal Subarachnoid Hemorrhage. J Stroke Cerebrovasc Dis. 25(2): p. 452-60.

How marijuana affects lung health is determined by how it’s consumed. In many cases, marijuana is smoked in the form hand-rolled cigarettes (joints), in pipes or water pipes (bongs), in bowls, or in blunts—emptied cigars that have been partly or completely refilled with marijuana. Smoked marijuana, in any form, can harm lung tissues and cause scarring and damage to small blood vessels. 1-2 Smoke from marijuana contains many of the same toxins, irritants, and carcinogens as tobacco smoke. 3 Smoking marijuana can also lead to a greater risk of bronchitis, cough, and phlegm production. 4-8 These symptoms generally improve when marijuana smokers quit.9-10

Secondhand marijuana smoke

The known health risks of secondhand exposure to cigarette smoke—to the heart or lungs, for instance—raise questions about whether secondhand exposure to marijuana smoke poses similar health risks. While there is very little data on the health consequences of breathing secondhand marijuana smoke, there is concern that it could cause harmful health effects, including among children.

Recent studies have found strong associations between those who said there was someone in the home who used marijuana or a caretaker who used marijuana and the child having detectable levels of THC — the psychoactive ingredient in marijuana. 5,11 Children exposed to the psychoactive compounds in marijuana are potentially at risk for negative health effects, including developmental problems for babies whose mothers used marijuana while pregnant. 8 Other research shows that marijuana use during adolescence can impact the developing teenage brain and cause problems with attention, motivation, and memory.12

References

  1. Tashkin, DP. (2013) Effects of marijuana smoking on the lung. Ann Am Thorac Soc. 10(3): p. 239-47.
  2. Moir, D, et al. (2008). A comparison of mainstream and sidestream marijuana and tobacco cigarette smoke produced under two machine smoking conditions. Chem Res Toxicol. 21(2): p. 494-502.
  3. U.S. Department of Health and Human Services. (2014). The Health Consequences of Smoking: 50 Years of Progress. A Report of the Surgeon General Cdc-pdf[PDF – 36MB]External. Atlanta, GA: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion, Office on Smoking and Health.
  4. Aldington, S, et al., Effects of cannabis on pulmonary structure, function and symptoms. Thorax, 2007. 62(12): p. 1058-63.
  5. Moore, C, et al. (2011). Cannabinoids in oral fluid following passive exposure to marijuana smoke. Forensic Sci Int. 212(1-3): p. 227-30.
  6. Tan, WC, et al. (2009). Marijuana and chronic obstructive lung disease: a population-based study. CMAJ. 180(8): p. 814-20.
  7. Taylor, DR, et al. (200). The respiratory effects of cannabis dependence in young adults. Addiction. 95(11): p. 1669-77.
  8. National Academies of Sciences E, and Medicine. (2017). The health effects of cannabis and cannabinoids: Current state of evidence and recommendations for researchExternal. Washington, D.C.
  9. Hancox, RJ, et al. (2015). Effects of quitting cannabis on respiratory symptoms. Eur Respir J, 2015. 46(1): p. 80-7.
  10. Tashkin, DP, Simmons MS, and Tseng, CH. (2012). Impact of changes in regular use of marijuana and/or tobacco on chronic bronchitis. COPD. 9(4): p. 367-74.
  11. Wilson KM, Torok MR, Wei B, et al. (2017). Detecting biomarkers of secondhand marijuana smoke in young children. Pediatr Res. 81:589–592.
  12. Broyd, SJ, et al. (2016). Acute and Chronic Effects of Cannabinoids on Human Cognition-A Systematic Review. Biol Psychiatry. 79(7): p. 557-67.

Marijuana use, especially frequent (daily or near daily) use and use in high doses, can cause disorientation, and sometimes cause unpleasant thoughts or feelings of anxiety and paranoia. 1

Marijuana users are significantly more likely than nonusers to develop temporary psychosis (not knowing what is real, hallucinations and paranoia) and long-lasting mental disorders, including schizophrenia (a type of mental illness where people might see or hear things that aren’t really there). 2

Marijuana use has also been linked to depression and anxiety, and suicide among teens. However, it is not known whether this is a causal relationship or simply an association.

References

  1. National Academies of Sciences E, and Medicine. (2017). The health effects of cannabis and cannabinoids: Current state of evidence and recommendations for researchExternal. Washington, D.C.
  2. Volkow ND, Swanson JM, Evins AE, et al. (2016). Effects of cannabis use on human behavior, including cognition, motivation, and psychosis: a review. JAMA Psychiatry. 73(3):292-297. doi:10.1001/jamapsychiatry.2015.3278.

Edibles, or food and drink products infused with marijuana and eaten, have some different risks than smoking marijuana, including a greater risk of poisoning. Unlike smoked marijuana, edibles can:

  • Take from 30 minutes to 2 hours to take effect. So some people eat too much, which can lead to poisoning and/or serious injury.
  • Cause effects that last longer than expected depending on the amount, the last food eaten, and medications or alcohol used at the same time.
  • Be very difficult to measure. The amount of THC, the active ingredient in marijuana, is very difficult to measure and is often unknown in edible products. Many users can be caught off-guard by the strength and long-lasting effects of edibles.

It is also important to remember that marijuana affects children differently than adults. Since marijuana has become legal in some states, children have accidentally eaten marijuana products that looked like candy and treats, which made them sick enough to need emergency medical care. 3

If you use marijuana products, keep them in childproof containers and out of the reach of children. For additional questions, you can contact your health care provider, your health department, the Poison HelplineExternal at 1-800-222-1222, or 911 if it’s an emergency.

The concept of marijuana as a “gateway drug”—where using marijuana leads a person to use other drugs—generates a lot of disagreement. Researchers haven’t found a definite answer yet. 1-2   However, most people who use marijuana do not go on to use other, “harder” drugs. 1

It is important to remember that people of any age, sex, or economic status can become addicted to marijuana or other drugs. Things that can affect the likelihood of substance use include:

  • Family history.
  • Having another mental health illness (such as anxiety or depression).
  • Peer pressure.
  • Loneliness or social isolation.
  • Lack of family involvement.
  • Drug availability.
  • Socioeconomic status. 2

References

  1. National Institute on Drug Abuse. Is marijuana a gateway drug? (2017). Rockville, MD: National Institutes of Health, National Institute on Drug Abuse.
  2. Robertson EB, David SL, Rao SA. (2003) Preventing Drug Use Among Children and Adolescents. A Research-Based Guide for Parents, Educators, and Community Leaders Cdc-pdf[PDF-725KB]External. National Institute on Drug Abuse, 2nd edn. NIH Publication no. 04-4212 (A). Bethesda, MD: US Department of Health and Human Services.
  3. Colorado Department of Public Health and Environment (2017) Monitoring Health Concerns Related to Marijuana in Colorado: 2016External.

Reference
  1. Substance Abuse and Mental Health Services Administration. (2017). Key substance use and mental health indicators in the United States: Results from the 2016 National Survey on Drug Use and HealthExternal. Rockville, MD: Center for Behavioral Health Statistics and Quality, Substance Abuse and Mental Health Services Administration.
  2. Batalla A, Bhattacharyya S, Yücel M, et al. (2013). Structural and functional imaging studies in chronic cannabis users: a systematic review of adolescent and adult findings. PloS One. 8(2):e55821. doi:10.1371/journal.pone.0055821.