Researchers are still studying to understand the full effects of marijuana use, particularly among youth. Further research is needed to develop a concrete understanding of the risks as well as any health benefits. In the meantime it is important to know that there are risks and there may be effects that we are not yet aware of.
However, based on the current science that is available, marijuana use may have a wide range of effects on health, both physical and mental. Within a few minutes after inhaling marijuana smoke, a person’s heart rate speeds up, the bronchial passages (the pipes that let air in and out of your lungs) relax and become enlarged, and blood vessels in the eyes expand, making the eyes look red. While these and other effects seem harmless, they can take a toll on the body.
Increased Heart Rate
When someone uses marijuana, heart rate—normally 70 to 80 beats per minute—may increase by 20 to 50 beats per minute or, in some cases, even double.1 This effect can be greater if other drugs are taken with marijuana. The increased heart rate forces the heart to work extra hard to keep up. Marijuana raises the heart rate for up to 3 hours after smoking.
There are many studies that report on the harmful health effects of smoking tobacco, such as cancer, respiratory disease (bronchitis, emphysema and asthma) and heart disease. While there have been few studies conducted on the effects of marijuana smoke, there is growing evidence that there are similar major health concerns for those who smoke marijuana.
There are more than 500 chemicals in marijuana and there is substantial evidence that marijuana smoke contains many of the same carcinogens found in tobacco smoke.1 Marijuana smoke irritates the lungs, and frequent marijuana smokers can have the same breathing problems that tobacco smokers have. These problems include daily cough and phlegm, more frequent lung illness, and a higher risk of lung infections.
Mental Health Problems
People with a genetic risk for developing schizophrenia, smoking marijuana during adolescence may increase the risk for developing psychosis and developing it at an earlier age.2 Researchers are still learning what the exact relationship is between these mental health problems, other mental health problems such as anxiety and depression, and marijuana use.
Effects on Quality of Life
Compared to nonusers, heavy marijuana users more often report lower life satisfaction, poorer mental health, poorer physical health, and more relationship problems.3
Users also report less academic and career success. For example, marijuana use is linked to a higher likelihood of dropping out of school
Effects of Smoking versus Eating
When marijuana is smoked, its effects begin almost immediately and can last from 1 to 3 hours. Decision making, concentration, and memory can suffer for days after use, especially in regular users.
If marijuana is consumed in foods or drinks, the effects of THC take longer to appear—usually 30 minutes to 1 hour—but may last for many hours. It is critical to be aware of the delayed effects of edibles. If someone consuming edibles is expecting the immediate effects of smoking marijuana, that person may continue to consume high amounts of THC after not feeling anything right away. Edibles have very high levels of THC and consuming too much can lead to severe reactions of paranoia, hallucinations, and psychosis.1
Effects of Combining Marijuana with Other Substances
It has not been heavily studied but combining marijuana with other substances can be dangerous, particularly combining marijuana with alcohol. The biggest impact of mixing marijuana and alcohol is the significant increase in impairment to judgment. The level of intoxication and secondary effects experienced can be unpredictable.
Also, because marijuana is used to treat nausea and vomiting in medical situations, it may be easier to drink alcohol until dangerously high blood alcohol levels are reached, as the normal body defense of vomiting when drunk may be muted by the marijuana.