Long Term Effects of Marijuana

When used chronically, marijuana can cause long-term health complications in the lungs, heart and brain. People who began using the drug during adolescence are at an increased risk for prolonged health problems, including marijuana addiction.
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Many people use cannabis for its euphoric effects. The drug can cause relaxation, drowsiness or excitement. But marijuana can also cause short-term symptoms such as restlessness, paranoia and heart palpitations.

Research on the long-term effects of marijuana use is limited. Cannabis is a Schedule I drug, a classification that restricts biomedical research on the substance and its effects. But existing research strongly links marijuana use to health problems that can last for years.

Cognitive Health

Marijuana can lead to long-term cognitive impairment. According to the National Institute on Drug Abuse, the drug can affect thinking, memory and learning in people who began using cannabis during adolescence.

A 2015 study by Northwestern Medicine showed that teens who smoked cannabis daily for about three years had an abnormally shaped hippocampus, which is the part of the brain that controls long-term memory. As a result, they experienced poor memory as adults.

Researchers at Duke University contributed to a study that found that people who began heavily using marijuana as adolescents and had a marijuana use disorder lost an average of eight IQ points from ages 13 to 38.

Recent reports have also suggested that people who quit smoking marijuana after having regularly used the drug since adolescence did not fully restore their brain function. Conversely, individuals who began using cannabis as adults did not experience the same cognitive decline.

A link between marijuana use and mental illness also exists. According to the National Institute on Drug Abuse, multiple studies indicate that cannabis use increases the risk for psychiatric disorders, including anxiety and depression. Using the drug can also exacerbate symptoms of schizophrenia.

Cardiovascular Health

Chemicals in marijuana called cannabinoids affect cardiovascular health. They can dilate blood vessels, raise resting heart rate and complicate heart pumping. According to a 2017 report by Harvard University, the risk for heart attack is much higher in the hour after smoking marijuana than it would be otherwise.

The report also stated that individuals with heart disease who experience stress develop chest pain more quickly if they’ve been smoking marijuana. Those with heart disease can also increase their risk for a heart attack when smoking marijuana.

Researchers have associated cannabis use with irregular heartbeat or ischemic stroke, but evidence of these health risks is limited.

Respiratory Health

Cannabis comprises various toxic chemicals. Hydrogen cyanide and ammonia can affect the bronchial passages and lungs, which can impede breathing. A report published in the Journal of General Internal Medicine showed that the drug contains similar levels of tar as those in tobacco smoke, but marijuana has up to 50 percent more carcinogens.

Marijuana affects the lungs. Cannabis smokers inhale more deeply and hold the smoke longer than cigarette smokers. As a result, they absorb five times more carbon monoxide and three times more tar. Exposure to these toxins increases the risk for long-term lung problems.

Regular cannabis users are more likely than nonusers to cough, wheeze or produce phlegm. They are also at an increased risk for lung infections, bronchitis and other significant respiratory health complications.

Marijuana and chronic obstructive pulmonary disease are also linked. COPD is a set of lung conditions that block airflow and make it difficult to breathe. People with the disease experience chest tightness, shortness of breath and swelling of the feet, legs and hands.

Can Marijuana Cause Cancer?

Researchers have wondered if cannabis use can lead to lung cancer because the drug contains carcinogens — cancer-causing chemicals also found in tobacco smoke. Research on this subject is limited and conflicting.

The lung biopsies of marijuana users have shown widespread changes to lung tissue that are considered precursors to cancer. A 2013 review of the health effects of chronic marijuana use linked cannabis to lung cancer. But several large-scale studies found no relationship between marijuana use and lung or upper airway cancer.

Marijuana’s association with cancer remains unclear. However, a 2017 study by the National Academies of Sciences, Engineering, and Medicine found limited evidence connecting cannabis smoking to nonseminoma testicular germ cell tumors. These tumors indicate testicular cancer.

The report also found no or insufficient evidence to support an association between marijuana use and incidence of non-Hodgkin lymphoma, malignant gliomas and cancers of the esophagus, prostate, cervix, anal canal, penis or bladder.


Research estimates that about 9 percent of marijuana users become dependent, according to the Office of National Drug Control Policy. The earlier people begin using marijuana, the more likely they are to become dependent on cannabis or other drugs later in life.

People who start using marijuana as teens are four to seven times more likely than adults to develop a marijuana use disorder, according to NIDA. Most marijuana use disorders are mild or moderate, which indicates dependence. But severe substance use disorders, or addiction, can occur in chronic cannabis users.

Addiction causes compulsive activity. Individuals with marijuana addiction seek the drug despite knowing the social, legal and health implications. They may steal money to purchase weed or engage in risky behaviors, such as driving while high.

Marijuana addiction can lead to health and financial problems. It can also cause social isolation and strained relationships. Those abusing marijuana are more likely to fail a drug test, which can result in unemployment.

If you are abusing marijuana, seek treatment. Marijuana rehab centers craft treatment plans specific to the individual. These facilities implement evidence-based psychotherapy techniques that allow clients to understand the underlying causes of their marijuana abuse.

Medical Disclaimer: DrugRehab.com aims to improve the quality of life for people struggling with a substance use or mental health disorder with fact-based content about the nature of behavioral health conditions, treatment options and their related outcomes. We publish material that is researched, cited, edited and reviewed by licensed medical professionals. The information we provide is not intended to be a substitute for professional medical advice, diagnosis or treatment. It should not be used in place of the advice of your physician or other qualified healthcare provider.

Matt Gonzales
Content Writer, DrugRehab.com
Matt Gonzales is a writer and researcher for DrugRehab.com. He graduated with a degree in journalism from East Carolina University and began his professional writing career in 2011. Matt covers the latest drug trends and shares inspirational stories of people who have overcome addiction. Certified by the Centers for Disease Control and Prevention in health literacy, Matt leverages his experience in addiction research to provide hope to those struggling with substance use disorders.

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