The Negative Health Effects of Marijuana

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Although legalization activists and many marijuana users believe smoking pot has no negative effects, scientific research indicates that marijuana use can cause many different health problems.

Marijuana is one of the most commonly used drugs in the United States. When smoked, it begins to affect users almost immediately and can last for 1–3 hours. When it is eaten in food, such as baked in brownies and cookies, the effects take longer to begin, but usually last longer.

Short-Term Effects of Marijuana

The short-term effects of marijuana include:

  • Difficulty thinking and problem-solving
  • Distorted perception (sights, sounds, time, touch)
  • Increased heart rate
  • Loss of coordination
  • Problems with memory and learning

Sometimes marijuana use can also produce anxiety, fear, distrust, or panic.

Brain Side-Effects of Marijuana Usage

The active ingredient in marijuana, delta-9 tetrahydrocannabinol or THC, acts on cannabinoid receptors on nerve cells and influences the activity of those cells. Some brain areas have many cannabinoid receptors, but other areas of the brain have few or none at all.

Many cannabinoid receptors are found in the parts of the brain that influence pleasure, memory, thought, concentration, sensory and time perception, and coordinated movement.

When high doses of marijuana are used, users can experience the following psychotic symptoms:

Marijuana's Negative Effects on the Heart

Within a few minutes after smoking marijuana, the heart begins beating more rapidly and the blood pressure can rise.

According to a review published in 2017, marijuana users' risk for a heart attack increases after smoking marijuana, compared to their general risk of a heart attack when not smoking.

Marijuana's Impact on Bone Health

Research published in 2017 found that people who smoke large amounts of marijuana on a regular basis have reduced bone density, which can increase the risk of bone fractures.

The study at the University of Edinburgh used DEXA-scan x-rays and found that heavy users of marijuana had a lower body weight and a reduced body mass index (BMI), which could contribute to loss of bone density. Heavy users were defined as those who had smoked more than 5,000 times during their lifetime.

However, another study published in 2017, looked at survey and health information for almost 5,000 adults and didn't find any association between decreased bone density and marijuana use.

How Marijuana Affects Lungs

Smoking marijuana, even infrequently, can cause burning and stinging of the mouth and throat, and cause heavy coughing. According to a review published in 2019, scientists have found that regular marijuana smokers can experience many of the same respiratory problems as tobacco smokers do, including:

  • Daily cough and phlegm production
  • Increased risk of lung infections
  • More frequent acute chest illnesses

Most marijuana smokers consume a lot less cannabis than cigarette smokers consume tobacco, however, the harmful effects of smoking marijuana should not be ignored.

Marijuana contains a similar amount of carcinogenic hydrocarbons as tobacco smoke and because marijuana smokers typically inhale deeper and hold the smoke in their lungs longer than tobacco smokers, their lungs are exposed to those carcinogenic properties longer, when smoking.

Cancer Risk and Marijuana History

According to a review published in 2015, one study found that marijuana smokers were three times more likely to develop cancer of the head or neck than non-smokers, but that study could not be confirmed by further analysis.

Because marijuana smoke contains three times the amount of tar found in tobacco smoke and a number of carcinogens, it would seem logical to deduce that there is an increased risk of lung cancer for marijuana smokers.

However, researchers have not been able to definitively prove such a link. Even though researchers have yet to "prove" a link between smoking pot and lung cancer, regular smokers may want to consider the risk, and further research is needed.

Marijuana Exposure During Pregnancy

Several studies have found that children born to mothers who used marijuana during pregnancy exhibit some problems with neurological development. These can include:

  • Hyperactivity
  • Impulsivity
  • Problems with executive function
  • Problems with sustained attention and memory
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