Marijuana affects users mentally in many ways while the user is high, but there is no evidence that it makes any changes to the users mental state when the high wears off. It does not appear possible for people to overdose on marijuana. Most of the physiological harms of marijuana are from the smoke inhaled into the lungs and not THC.

While marijuana is not known to weaken or strengthen the immune system as a whole, people with immune system deficiencies should avoid marijuana smoke because it weakens alveolar macrophages ability to defend against fungi, bacteria, and tumor cells in the lungs. Marijuana smoke does increase the risk of respiratory illness and heavy smokers will have changes in the lining of the respiratory tract.

Medical Marijuana Effects on Users | Fact or Faction

There is no conclusive evidence that marijuana can cause cancer to date, but there is a strong likelihood that further research will find correlations. First time users of marijuana will experience a rapid heart beat for the first few minutes of inhaling, and some users will also have an increase in blood pressure for a few minutes.

First time users will also have a decrease in testosterone or estrogen. Both of these “first time user” effects cease to exist in more experienced users. Pregnant women should avoid inhaling marijuana smoke because it causes a higher mutation rate, but has little effect on the long-term cognitive abilities of the child.

Smoking marijuana (or inhaling any smoke) can cause health problems. But I feel that people that smoke marijuana in moderation are putting themselves at less risk than those that smoke tobacco cigarettes in relative moderation and putting themselves at less risk than those that drink heavily (whether occasional binge drinking or drinking more than a moderate amount on a daily basis). I do not feel that marijuana poses enough threat to make it an unconscionable health problem for our society.

But I do feel that those that smoke marijuana heavily are taking more risks than can be justified. Ultimately I think that people should know the risks involved and make their own decision as to whether or not they are willing to take on those risks.

I think the best way I can end this article is to leave you with someone else’s take on how safe marijuana is on a relative scale. A few years back the United States’ Drug Enforcement Agency had a trial lasting a couple years to determine if medical marijuana was safe enough to be considered for medical use. The case was heard in the court DEA’s own administrative court. After the DEA’s judge read thousands of pages of testimony and heard from dozens of witnesses he declared that marijuana is “one of the safest therapeutically active substances known to man.”

Marijuana is not associated with any increase of mortality. Most physiological harms that are attributed to marijuana are actually from the act of smoking, or inhaling smoke. They are very similar to tobacco smoke.

THC and the Immune System

THC both increases and decreases different types of immune system cells, but after much research there is no proof that it either weakens or strengthens the immune system.

Marijuana Smoke

Marijuana smoke is very similar to tobacco smoke, and tobacco smoke has been found to cause lung diseases like cancer and emphysema. Marijuana users typically do not smoke anywhere near the volume of marijuana as tobacco smokers smoke tobacco. One joint usually has about half the smokable substance as one tobacco cigarette.

But because marijuana is not usually filtered and users tend to hold the medical marijuana in their lungs for longer periods of time, up to four times as much tar can be deposited in the lungs per ounce of smoked marijuana as an ounce of tobacco. There is an additive effect of smoking both tobacco and marijuana.

Chronic Bronchitis

Smoking marijuana increases the users risk of respiratory illness. Interestingly people that have been smoking marijuana 10 years or more are usually not at a greater risk of having respiratory problems, but those that have been smoking for less than 10 years are. This is most likely because the people that do have respiratory problems discontinue smoking marijuana, and those that don’t quit usually haven’t had many problems. From a random sample 15-20% of people who smoke marijuana but not tobacco will report chronic bronchitis, and 20-25% of those that smoke tobacco but not marijuana will report chronic bronchitis. Those that smoke both will be at a higher risk.

Bronchial Tissue Changes

Heavy marijuana smokers will have changes in the lining of the respiratory tract. There will be more redness and swelling of the airway tissues and increased mucus secretion. Smokers of marijuana and tobacco have significantly more cellular and molecular abnormalities in the bronchial epithelium cells. There is an association with those abnormalities and increased risk of cancer. A marijuana only smoker that smokes about 21 marijuana cigarettes a week has about the same amount of abnormalities as a tobacco only smoker that smokes about 25 tobacco cigarettes a day. Once again those that smoke both will have an additive effect.


To date, there is no conclusive evidence that marijuana causes cancer in humans. However, marijuana has many of the same carcinogens as tobacco. The problem with finding a correlation with marijuana and cancer is that respiratory cancer requires a long-term exposure to smoke. Marijuana usage has only become popular since the late 1960’s, and most people only smoke marijuana when they are younger. As some habitual marijuana smokers get older and have been smoking marijuana for several decades there could very well be proof that marijuana causes cancer, but as of today there is no conclusive evidence that this is the case.

Using Cannabis During Pregnancy

THC can interfere with the implantation of the embryo making it harder for a woman that smokes marijuana to get pregnant. Like tobacco smoke, pregnant women should not expose themselves and their babies to marijuana smoke. Babies born to mothers that smoked marijuana during pregnancy weighed an average of 3.4 ounces less than other babies. Newborns of mothers that smoke either tobacco or marijuana have a higher mutation rate than those of non-smokers.

Jamaican women often drink marijuana tea as opposed to smoking marijuana and their children do not show any neurobehavioral problems. Whereas the cognitive abilities of babies born to mothers that smoked marijuana during pregnancy often show detectable deficits up until the age of 5, when the deficits are no longer detectable (this is for global measures of intelligence such as language development, reading scores, and visual or perceptual tasks).

There has been evidence that children exposed to marijuana parentally may exhibit deficits in executive function as late as 9-12 years old. That means they have trouble planning, anticipating, and suppressing behaviors that are incompatible with a current goal, and are often described as hyperactive or impulsive. However, in the case of the executive function the cause of the deficit could be related to the reason the mother was smoking marijuana during pregnancy, and not necessarily the marijuana exposure.

Marijuana use can disturb the T and B cell function of the bodies lymphocytes, but it is a very small disturbance that is usually within normal limits. Just like tobacco smokers, alveolar macrophages, the lungs immune-effector cells, have difficulty destroying fungi, bacteria, and tumor cells in the lungs. For this reason people with immune system deficiencies should avoid marijuana usage.

Cardiovascular System

Marijuana smoke and THC can cause a rapid heartbeat of up to 20-100% above the baseline during the first 10-20 minutes of smoking, and some users have an increase in blood pressure. Experienced users of marijuana have a tolerance for this effect, so it is not usually seen in marijuana users that have been using marijuana regularly. The tolerance can be built in as little as a week of frequent usage. The cardiovascular changes usually are insignificant to younger users. Older people should be aware of this fact though, as their bodies typically cannot handle cardiovascular changes as well.

Reproductive System

Marijuana and THC inhibit the release of luteinizing hormone, which is responsible for signaling the release of testosterone and estrogen. Again a tolerance is seen in this effect as well, meaning regular users of marijuana typically do not have any reduction in testosterone and estrogen, only those that have just begun smoking marijuana.