Marijuana & the Human Body

Endocannabinoid System

When a person uses marijuana, the effects can range vastly, from pain relief to relaxation to feeling high. Those effects occur because of the way that it interacts with the body’s endocannabinoid system.

The endocannabinoid system (ECS) acts as the body’s balancing tool, keeping functions like mood, sleep, and appetite in check. It’s also responsible for learning and memory, emotional processing, body temperature, and other aspects of the body’s minute-to-minute functionality.

In the human body, delta-9-tetrahydrocannabinol (THC), the psychoactive compound in marijuana, disrupts the normal balance that the ECS maintains. This can create a variety of effects, explaining why different people may have different reactions to marijuana depending on their genetic make-up.

 Major Systems Affected by Marijuana

Marijuana can affect many systems in the body — especially the brain and heart. While some people use it without problems, it’s important to know the risks, especially for teens and young adults.

• Brain & Nervous System

  • Alters memory, attention, and learning capacity 

  • Disrupts development in adolescent brains 

  • High doses can trigger psychosis, especially in vulnerable individuals 

  • Associated with increased risk of anxiety, depression, and suicidal thoughts in teens and frequent users

• Heart & Circulatory System

  • Increases heart rate (20–50 bpm within minutes) 

  • Can raise the risk of heart attack, especially in older adults or those with pre-existing conditions 

  • May cause spikes in blood pressure 

• Lungs & Respiratory System

  • Smoking marijuana can irritate lungs and lead to chronic bronchitis

  • Heavy users may experience persistent cough, wheezing, and phlegm 

  • Vaping THC oils has been linked to EVALI (e-cigarette or vaping-associated lung injury) — 80% of EVALI cases involved THC-containing products

• Digestive & Appetite Systems

  • Often increases appetite ("the munchies") 

  • Can cause nausea and vomiting in high doses or with chronic use (Cannabinoid Hyperemesis Syndrome) 

  • ER visits for marijuana-related GI symptoms have increased significantly in states with legal cannabis.

• Immune & Endocrine Systems

  • THC may suppress immune function, especially in heavy users

  • Can disrupt hormone regulation, potentially affecting reproductive health in both men and women 

  • Studies suggest long-term use may lower sperm count and disrupt ovulation

• Behavioral & Mental Health Impacts

  • Impaired judgment, decision-making, and reaction time 

  • Increased risk of car accidents, school dropout, and substance dependency 

  • Possible link to amotivational syndrome — reduced initiative and goal-directed behavior in some heavy users 

  • Daily marijuana users are three times more likely to develop cannabis use disorder