Health Risks of Marijuana

When posed with the question “is weed harmful?,” many people will say no. However, relaxed societal views and an increasing number of states legalizing this drug don’t change the fact that there are many negative long-term effects of weed on the brain and body.

So, what are the consequences of smoking weed? They extend beyond losing your motivation and getting “the munchies”. In this article, we’ll discuss some of the many health effects of marijuana.

Side Effects of Smoking Marijuana


The high that arises from delta-9-tetrahydrocannabinol (THC) when smoking marijuana includes short-term effects such as:1

  • Altered senses and perception of time.
  • Mood changes.
  • Movement and coordination problems.
  • Difficulty thinking clearly and solving problems.
  • Impaired memory.

In high doses, marijuana can also cause hallucinations and psychosis. Because marijuana is becoming increasingly potent, there is an increased risk of experiencing symptoms.1

Marijuana can be consumed in other ways other than smoking, including by consuming edibles (cookies, brownies, gummies, etc.), brewing into tea, or dabbing THC-rich resins (butane hash oil). While there may be some variation in how long it takes for the effects to arise (edibles can take much longer to produce effects than smoking or dabbing), they are essentially the same regardless of the method of use.1

Because it takes longer for edibles to produce a high, some users may consume increasing amounts in an attempt to speed up the onset of the effects. By doing so, they may subject themselves to some of the more harmful effects, such as psychotic symptoms, and these uncomfortable side effects tend to last longer as the drug moves slowly through the body’s gastrointestinal system.1

Are There Long-Term Effects of Marijuana?

The effects of marijuana are not limited to the short-term side effects. Chronic marijuana use can impact the body and mind in numerous ways. For example, it can:2

  • Negatively affect brain development in teens and young adults.
  • Increase the risk of cardiovascular problems, such as heart disease.
  • Harm the lungs.
  • Bring on or worsen distressing mental health symptoms.

These long-term effects are discussed in more detail below.

Long-Term Effects of Weed on the Brain

Teen girl having trouble concentrating

Among marijuana’s most troubling effects are those on the brains of young people. It takes about 25 years for the brain to fully develop.3 When a person uses weed in their adolescent/teenage years, marijuana can impair their normal brain development, causing problems in their brain’s ability to make connections in the areas that are required for:2

  • Attention.
  • Memory.
  • Learning.

The changes that occur in the brains of young people who use marijuana may be long-lasting, and research is still being performed to determine if some changes may be permanent.1,2

The effects of weed on the brain’s development are impacted by factors such as:2

  • How much THC is in the marijuana (its potency).
  • Age at first use.
  • Frequency of use.
  • Whether marijuana is used along with other drugs such as alcohol.

Marijuana and Pregnancy

Marijuana use by pregnant mothers may also impact brain development in babies. Research has linked prenatal marijuana use to problems for the children that include:2

  • Attention and memory problems.
  • Difficulty with problem-solving.
  • Behavioral issues.

Heart and Cardiovascular Problems

Using weed may harm the cardiovascular system in several ways. Research suggests that marijuana use may result in:2,4,5,6

  • A mild increase in blood pressure.
  • Rapid or irregular heart rate.
  • Increased heart disease or heart failure risk.
  • Increased risk of stroke.

Those who have coronary heart disease, or who are at high risk of developing it, may be especially vulnerable to the effects of weed on the heart.7

Some of the cardiovascular effects are linked to smoking the substance. While smoking marijuana effectively delivers THC into your body, that’s not all you’re getting. You’re also delivering the types of toxins into your body that are in tobacco smoke, which can harm both the cardiovascular system and the lungs.2,8

Marijuana’s Effects on the Lungs

Severe cough

Smoking marijuana can cause respiratory health problems in a way similar to tobacco smoke. Marijuana smoking irritates the throat and lungs and may cause a severe cough. Smoking weed may increase the risk of the following respiratory health problems:1,2

  • Inflammation of the airway.
  • Damage to the lung’s tissues.
  • Increased airway resistance (resistance to flow of air during breathing).
  • Lung hyperinflation resulting from air trapped in the lungs.
  • Increased cough and production of phlegm.
  • Chronic bronchitis.

Use of certain THC-containing vape products has been linked to reports of serious lung illness and death. Vitamin E acetate, which is added to some e-cigarette products that contain THC, is very strongly associated with the risk of e-cigarette, or vaping, product use-associated lung injury (EVALI). Both the CDC and FDA advise against use of THC-containing vape or e-cigarette products.1,9

Can you get lung cancer from smoking weed?

Currently, there is no definitive answer as to whether marijuana smoking causes lung cancer. Marijuana does contain cancer-causing agents; however, research has failed to show that weed causes cancer.1

While those who smoke marijuana do inhale it and hold it longer, they may smoke it less frequently than a person might smoke tobacco because the effects of weed last longer. The connection between marijuana and cancer is also difficult to make because many marijuana users also smoke tobacco.1

Nausea and Vomiting

Using marijuana repeatedly may lead to a health problem called Cannabinoid Hyperemesis Syndrome (CHS). Symptoms include:1

  • Intense nausea.
  • Abdominal pain.
  • Repeated vomiting.
  • Dehydration.
  • Loss of appetite/weight loss.

CHS is more common among regular high-dose marijuana users than those who use only occasionally.10,11 Those who suffer from this syndrome may require emergency care and/or hospitalization.1,10

Marijuana’s Effects of Mental Health

Troubled woman

Regular marijuana use and high-dose marijuana use can cause mental health symptoms that include disorientation, anxiety, and paranoia.2

Using marijuana may increase a person’s chances of experiencing psychotic symptoms such as hallucinations and paranoia. Research has found that everyday use of high-potency weed may increase the risk of psychosis by up to 5 times.12 Other factors that may contribute to this risk include how much the drug is used, the age at first use, and genetics.12

For those who are genetically vulnerable to schizophrenia, using marijuana may heighten their risk of developing this disorder. For those who already suffer from schizophrenia, marijuana use may worsen the course of the illness.12

Repeated marijuana use is also associated with amotivational syndrome, which reflects a lack of motivation to partake in activities one would normally find pleasurable or rewarding.12

Marijuana and Addiction Risk

Research has found an association between marijuana use and an increased risk of:12

  • Nicotine dependence.
  • Alcoholism.
  • Marijuana use disorder or other substance use disorders.

According to the National Institute on Drug Abuse, up to 1/3 of people who use marijuana have a marijuana use disorder. Marijuana use that begins in adolescence (prior to age 18) increases the risk of a marijuana use disorder by up to 7 times.13

A marijuana use disorder or other substance use disorder is characterized by a compulsion to keep using a drug despite the negative consequences that arise from doing so. A person struggling with an addiction to marijuana, alcohol, or other drug may struggle with an inability to quit despite repeated attempts to do so, problems attending to personal obligations due to substance use, a growing tolerance that prompts increased use, and withdrawal symptoms upon attempting to quit.14

If you’re using marijuana or any other substance and you’re unable to stop, we’re here for you. At Recovery First, we have a full array of programs, from outpatient rehab to inpatient therapy, that can help you achieve recovery.


  1. National Institute on Drug Abuse. (2019). Marijuana DrugFacts.
  2. Centers for Disease Control and Prevention. (2018). Health Effects.
  3. Arain, M., Haque, M., Johal, L., Mathur, P., Nel, W., Rais, A., Sandhu, R., & Sharma, S. (2013). Maturation of the adolescent brainNeuropsychiatric disease and treatment9, 449–461.
  4. Rumalla K, Reddy AY, Mittal MK. Recreational marijuana use and acute ischemic stroke: A population-based analysis of hospitalized patients in the United States. J Neurol Sci. 2016 May 15;364:191-6.
  5. Heart and Stroke Foundation of Canada. (n.d.). Cannabis, heart disease, and stroke.
  6. American College of Cardiology. (2017). Marijuana Use Associated with Increased Risk of Stroke, Heart Failure.
  7. Sidney S. Cardiovascular consequences of marijuana use. J Clin Pharmacol. 2002 Nov;42(S1):64S-70S.
  8. National Institute on Drug Abuse. (2020). What are marijuana’s effects on lung health?
  9. Centers for Disease Control and Prevention. (2020). Outbreak of Lung Injury Associated with the Use of E-Cigarette, or Vaping, Products.
  10. Cedars-Sinai. (n.d.). Cannabinoid Hyperemesis Syndrome.
  11. DeVuono MV, Parker LA. Cannabinoid Hyperemesis Syndrome: A Review of Potential Mechanisms. Cannabis Cannabinoid Res. 2020 Jun 5;5(2):132-144..
  12. National Institute on Drug Abuse. (2020). 2020, May 28. Is there a link between marijuana use and psychiatric disorders?
  13. National Institute on Drug Abuse. (2020). Is marijuana addictive?
  14. American Psychiatric Association. (2013). Diagnostic and statistical manual of mental disorders (5th ed.). Arlington, VA: Author.

About The Contributor

Ryan Kelley, NREMT
Ryan Kelley, NREMT

Medical Editor, American Addiction Centers

Ryan Kelley is a nationally registered Emergency Medical Technician and the former managing editor of the Journal of Emergency Medical Services (JEMS). During his time at JEMS, Ryan developed Mobile Integrated Healthcare in Action, a series... Read More

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