Within the United States, more people use marijuana than any other illicit drug, the National Institute on Drug Abuse (NIDA) publishes. It is most commonly smoked or vaped, but it can also be ingested in the form of edibles or brewed in a beverage. The National Survey on Drug Use and Health (NSUDH) reports that in 2014 more than 22 million Americans were considered current users of marijuana.

Physical Harms of Abusing Marijuana

The active chemical in marijuana, delta-9-tetrahydrocanabinol (THC) acts on cannabinoid receptors in the brain, taking effect rather quickly after ingestion or inhalation of the drug. It alters the senses and perceptions, and it gives users a euphoric feeling, or “high.”

Marijuana is often heralded for its potential medicinal purposes as well. It may reduce anxiety, help to calm a person, minimize nausea, and increase appetite levels in chronically ill individuals. Many states have legalized marijuana for both medicinal and recreational purposes, although the drug remains a Schedule I controlled substance by the Drug Enforcement Administration (DEA), and therefore federally illegal.

Marijuana is considered a harmful substance with both short-term and long-term effects of abuse. It impacts many different parts of the brain and body when abused, such as:

  • Cardiovascular system by disrupting heart rate and blood pressure
  • Lungs
  • Regions of the brain that control impulses, process rewards, make decisions, and are involved in learning and memory
  • Immune system

Damage to the Body from Marijuana Abuse

Marijuana can raise heart rate by 20-50 beats per minute, or even double it in some cases, quadrupling the risk for heart attack within the first hour of taking the drug, NIDA warns. It may also cause a person to feel dizzy or lightheaded upon standing, called orthostatic hypotension, which may contribute to accidents or injuries from falling down.

Air pockets may form in between the lungs, as well as between the lungs and the wall of the chest. Air bubbles may also form in the lungs themselves. These air pockets or bubbles can burst randomly, which may be life-threatening. Individuals who smoke marijuana on a regular basis may develop chronic obstructive pulmonary disease (COPD) and be at an increased risk for lung damage, lung infections, and lung cancer, the American Thoracic Society publishes.

The American Lung Association warns that marijuana use can lower a person’s immune system and potentially put them at a greater risk for lower respiratory infections. It can also lower the body’s ability to fight off other infections and diseases, especially in those who are HIV positive.

In 2011, nearly a half-million people in the United States received emergency medical treatment for a negative reaction to marijuana abuse, the Drug Abuse Warning Network (DAWN) reports. Marijuana use can not only be harmful to the body; it can also impair a person’s reaction time, reflexes, motor coordination, and the way a person thinks, possibly leading to more risk-taking behaviors, accidents, and injuries.

Effects of Marijuana on the Brain and Cognition

Not long after taking it, marijuana enhances relaxation, elevates moods, alters the perception of time and the senses, and short-circuits learning and memory functions. With regular use, marijuana may actually damage the brain and impact cognition.

The brain uses “executive functions” to process information, make decisions, control impulses, solve problems, plan and organize, remember things, and regulate emotions and behaviors. Marijuana disrupts the brain’s executive functions, and some of these abilities, such as those related to planning and decision-making, may be impaired long-term with chronic marijuana abuse, the Journal of Addiction Medicine publishes. Some of these cognitive deficits may not be recoverable even with abstinence.

Marijuana use is also linked to an increased risk for psychosis and the onset of schizophrenia in individuals who are predisposed to the disorder, the Indian Journal of Psychiatry reports. In many people, marijuana use may not have the desired calming effect. Around 20-30 percent of individuals who use marijuana recreationally suffer from panic attacks and intense anxiety, Harvard Health publishes.

Marijuana is considered to be an addictive substance, as regular use can create chemical and physical dependence on the drug that can lead to an inability to control use. NIDA reports that nearly a third of those who use marijuana suffer from dependence and potentially addiction to the drug. Individuals who are dependent on marijuana may battle difficult withdrawal symptoms when the drug leaves the body and feel irritable, agitated, depressed, unmotivated, and anxious. They may also have difficulties sleeping.

Using marijuana before the brain is fully developed in adulthood increases the risk for addiction and cognitive deficits. The 2013 NSDUH found that in individuals who used marijuana at age 14 or younger were around four times more likely to battle drug dependence and addiction in adulthood than those who waited until after age 18 to try it. NIDA also warns that marijuana usage can even decrease a person’s IQ up to eight points when abuse of the drug begins during adolescence or young adulthood.

Effects of Marijuana on the Brain and Cognition

Brain structure may be physically impacted by regular cannabis usage during the teen years, the journal Current Addiction Reports publishes. Several parts of the brain that are helpful in regulating moods, making decisions, learning and remembering things, motivation, and willpower are not fully developed, and they are disrupted by marijuana abuse during this important developmental stage. Marijuana use, especially at a young age, can have lasting physical side effects and negative consequences that can linger indefinitely.