10 Most Common Health Side Effects of Using Marijuana

This article replaces the “10 Most Common Side Effects of Using Marijuana” article that appeared here previously in the interests of having a more balanced and realistic portrayal of marijuana.

Commonly Disputed Side Effects of Using Marijuana

Marijuana, most commonly known as “weed” or “pot,” can be smoked, eaten, vaporized or (uncommonly) made into a tea to produce a “high” feeling. This high is caused by the primary psychoactive compound in marijuana, tetrahydrocannabinol (THC), interacting with the body’s cannabinoid receptors.

The high that marijuana induces is extremely subjective and is experienced by people differently but generally will include feelings of relaxation, mild paranoia and anxiety, alteration of visual, auditory, and olfactory senses, fatigue, and stimulation of the appetite.

And although no deaths have been directly related to smoking marijuana, it has been shown to produce some potentially negative side effects in people. Many of these side effects, although backed by scientific studies, have also been disputed and discredited by other scientific studies and reviews, making marijuana a hotly disputed topic.

Physical side-effects

Although almost all reported side effects of smoking marijuana are disputed, some common ones that can easily be observed are reddening of the eyes, dryness of the mouth and increase in heart rate. It has also been linked to a decrease in intra-ocular pressure, which is why it is sometimes prescribed for people with glaucoma (a condition that involves pressure on the eye).

Mental side-effects

Many studies have been done about marijuana’s effects in regard to bipolar disorder, depression, mood swings and schizophrenia, but no reliable conclusions have been achieved, as there are just as many studies that have drawn a correlation between marijuana use and these disorders as there are scientific studies and scientific peer reviews that say there is no correlation at all. For example, in one study, “Moderation of the Effect of Adolescent-Onset Cannabis Use on Adult Psychosis by a Functional Polymorphism in the Catechol-O-Methyltransferase Gene: Longitudinal Evidence of a Gene X Environment Interaction”published in Biological Psychiatry, researchers claimed to find a link between marijuana use and psychosis, however, a different study “Genotype effects of CHRNA7, CNR1 and COMT in schizophrenia: interactions with tobacco and cannabis use” published in The British Journal of Psychiatry has cast doubt on those findings. There are dozens of these types of studies that make conclusions one way or the other depending on how the results are interpreted, making them all relatively useless when trying to pinpoint long-term health effects of marijuana.

And although a German study allegedly found that marijuana use was a direct causal factor in some cases of schizophrenia, the fact that marijuana use has skyrocketed in most countries in the past few decades while cases of schizophrenia and psychosis have stayed the same makes that study’s conclusion seem highly doubtful.

Another study published in The British Journal of Psychiatry, “Causal association between cannabis and psychosis: examination of the evidence,” found that while marijuana generally exacerbates the onset of psychosis in people who are predisposed to having the condition, it won’t cause a condition in a healthy person.

Several studies have also been published that both claim and dispute marijuana’s negative side effects on the development of adolescent brains, long and short term memory and the capacity for learning.


In his book The Science of Marijuana, professor of pharmacology at the University of Cambridge Leslie L. Iversen says between 10 to 30 percent of regular marijuana users will develop a dependency on it but only about 9 percent will develop a serious addiction to it.

In the book, Iversen reviews decades of international laboratory and survey research on marijuana.

Compared to harder drugs like cocaine or heroin (or even the perfectly legal nicotine) marijuana has few severe withdrawal symptoms and the majority of people who use it recreationally are able to quit easily. Withdrawal symptoms might include mild anxiety, depression, nausea, insomnia and some gastrointestinal problems.


Although there has been no long-term study linking marijuana use to cancer, it certainly cannot be ruled out. (And smoking it certainly does not cure cancer like some marijuana users like to claim.)

THC is a relatively harmless drug for the human body but the problem is that to get THC into their systems, most people choose to smoke it and that’s where it can become dangerous. Scientific analyses of marijuana smoke, cited in Iversen’s book, have identified at least 6,000 of the same chemicals in marijuana smoke as are present in tobacco smoke. Smoked marijuana and smoked tobacco are chemically very similar, the main difference between them being the THC in marijuana and the nicotine in tobacco.

A potent carcinogen in tobacco smoke, benzo(α)pyrene, is present in higher amounts in marijuana smoke. And because marijuana smokers usually hold the smoke in their lungs longer than cigarette smokers, this increases the amount of tar deposited in the respiratory system.

Using vaporizers, water pipes or ingesting marijuana by eating it are ways to help avoid some of the chemical found in marijuana smoke.

Respiratory Health

But despite marijuana smoke being quite similar to tobacco smoke, several studies have been conducted and have concluded that even daily smoking of marijuana has little negative effect on the body’s respiratory system.

Dr. Donald Tashkin, who has done extensive research on marijuana smoke, has said “that essentially there is no significant relationship between marijuana exposure and impairment in lung function.” He also added that this could be due to THC’s anti-inflammatory effect.

Marijuana acts as a gateway drug

Many anti-marijuana activists like to point to the theory that marijuana acts as a gateway drug for young people, leading them to try other, harder drugs down the road. However, there has been no conclusive study to prove this theory and because of the fact that both alcohol and nicotine tend to be much more readily available and are often used in conjunction with marijuana by young people, the theory has been impossible to conclusively prove.

The effects and side effects of marijuana will likely continue to be studied, debated, hyped, lied about, proven and disproven moving forward. The only sure thing every person can agree on is that marijuana will continue to be hotly debated as laws surrounding it continue to soften.


112 comments to 10 Most Common Health Side Effects of Using Marijuana

  • Joe

    Marijuana like other illegal drugs has side effects which can be damaging in many ways. This is true. Too often smokers come on web sites like this and attempt to justify their pathetic need to smoke this vile stuff. It isn’t just the effect on the smoker but the effect on other people in their life.

    Only selfish losers who haven’t got the guts to deal with life have anything to do with these drugs.

  • cicme

    Hi.I read many comments about this drug. I now many people who using this and also i know many people who dont use this. When you look them some of them are sukcesful people and some are looser… Some of them are crazy and some are normal… Some have sex problem and other dont.. Some of them have healt problem and some dont. And this problems have adict of marijuana and non adict. Marijuana is not heroin. I think is less danger than alcohol and cigarets… And mc donalds ;) . Use it with caution. In uk study of top 20 moust danger drugs heroin and cocain is on 1,2 place. Alcohol is on 5 place. Cigarets is 8. And weed is 11 place. So think about that… Do sport and dont use drugs

  • Ginnie

    While researching, I ran across these comments. I quit smoking MJ a number of years ago, as I developed Barretts Esophagus. I have been told there is DNA changes to my thoat. I was NOT a heavy smoker. So far I have found no research on this topic, except some vague references. Hard research evidently is not there to support these issues. If someone can show me different, that MJ was the cause of this, I would appreciate it.

  • Ginnie

    I quit smoking MJ a number of years ago. I ran across these comments doing research, and I would like to smoke again, though a vaporizer. I was never a heavy smoker. I developed Barretts Esophagus, and was told I have DNA changes to my throat. This is why I quit. Noone can give me a straight answer if MJ was directly responsible for this. Has anyone out there experienced throat problems? Research is all over the place and none is proven. thankyou

  • stacey

    hey i smoke weed and it calms me down but dont mix it with alcohol coz my heart was beating fast but that is all over now and everything is good

  • stacey

    and smoking weed is healthy it calms u down u only live once so fuck what other people say

  • Leahcim

    for me, it has many positive effects. i think it depends on the intention of an individual why he/she smoke herb. I’m just 19 years old and marijuana made me a better person. When i was in high school, i got addicted to alcohol and it somewhat almost destroyed my life. when i get drunk, i get irritated easily and sometimes it leads me to do violent actions. Then, when my college years started. i started smoking herb and listen to reggae music. when i get high. my mind is in a state of peace. my sense of appreciation of things around me got higher. People say that you’ll get lazy when you are under the influence of weed, i dont think so. with or without the influence of weed. people always has the tendency to get lazy, it’s up to you how to overcome it. i think there’s nothing wrong with getting high as long as you know how to control yourself and your intention is good. much love <3

  • Fantasy

    Well, it does has its worse side effects like any other drug but one can’t neglect the happy part of it. I did not try so many drugs but I’m sure this drug is controllable in a way that you don’t get addicted to it. You have better control over yourself unless any other drug. What I’ve experienced using weed is so much pleasant, thought regret at the end. It results in sweet temptation in your whole body and you start to enjoy things around, you focus on people, their words, you enjoy music, you enjoy laughing at each other because you think everybody has gone out of their minds :p One thing more, you develop new ideas like taking things in a unique pleasant way, I mean you become creative in a sense and ya you eat much :p esp you wish to have cool juicy things, etc. The worst thing I have come to know about this is that you get pale and tend to loose your intelligent skills of your mind. You take much longer time to solve or calculate things than before.

  • Chris

    Beer drinkers lose their mind and beat their loved ones, kill people with knifes guns cars. A pot smoke most likely do this if he isn’t using another substance. Also he will remember killing someone I can bet you that,

  • Why must ones opinion be viewed and judged period. I smoke, do I shun those who don’t, no. I am a active member of society, with a job to boot, and I smoke daily, several times daily. It not only gives the hand of no longer needing prescription medication and it has regulated my diet and mood. Though not justifying, just commenting why must anyone persecute another for wanting to live their life, bc if me getting lifted effects you then you must be the lifeless loser.

  • Ahealthyhorse@yahoo.com

    It all depends on how you use it guys. Everything in moderation.

  • uriel Vasquez

    I have smoke mj ones and its nit the best feeling people say its the best feeling not ist not.at first I didn’t know what were the side effects by reading this article am a little aware of the feelling after a month or two I still have the felling of my vision sometime I fell like a gona faint or my vision is wierd the come the anxiety thax to this article am aware of what might happen to me

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