10 Effects of Marijuana on the Body and Brain

Marijuana is one of the most commonly consumed abused drugs despite being illegal in most countries. 

Today there is an open debate about its legality since many people consider it a soft drug.  In fact, more and countries now have legalized its therapeutic or recreational use.

consequences of marijuana

But is it really a soft drug?  What effects does marijuana cause in our body?  For our behavior?

In this article I will try to answer these questions and more through a simple list of the effects of marijuana on the body and brain.

What is Marijuana?

Marijuana or cannabis is a commonly abused drug whose active ingredient is THC (delta-9-tetrahydrocannabinol).  THC is mainly found in the buds of the cannabis sativa plant, which the users of the drug tend to consume only the ground buds (“mary”), pollen (“pollen”), or pressed pollen (“hashish”).

This drug is usually consumed by smoking a mixture of the substance with tobacco to make it easier to burn and inhale.  This form of administration causes the effects to be produced almost instantly since the active ingredient is absorbed through the capillary veins in the lungs and alveoli and it quickly reaches the bloodstream and the brain. 

Once it reaches the central nervous system, THC binds to the CB1 cannabinoid receptors.  The existence of THC receptors in our body indicates that our own body naturally produces substances that bind to these receptors that have an effect similar to THC. 

The endogenous substances that bind to these receptors are lipids, and the most well-known are anandamide and 2-AG (2-arachidonoylglycerol).  In addition to cannabis, there are other products or substances that contain anandamides that bind to these receptors, such as chocolate. 

Also, the number of cannabinoid receptors in our central nervous system is higher than any other neurotransmitter, and in certain areas of the brain, their number is up to 12 times greater than the number of dopamine receptors. 

The cannabinoid system primarily affects the cerebellum, which controls motor coordination; the brainstem which regulates vital functions; and the striatum, hippocampus, and amygdala which are responsible for reflexes, memory, and anxiety. 

Marijuana use is widespread throughout the world and the number of consumers is growing.  The following list shows the countries where the use of marijuana is most prevalent:

TOP 10



Countries with the Most  Consumers of Marijuana

Country Consumer Population Estimation Year
1.   Iceland 18.30% 2012
1.   United States 15.40% 2013
1.   New Zealand 14.60% 2007
1.   Nigeria 14.30% 2008
1.   Canada 12.20% 2012
1.   Bermuda 10.90% 2009
1.   Australia 10.16% 2013
1.   Spain 9.60% 2011
1.   Zambia 9.50% 2004
1.   Czech Republic 9.20% 2012

Source: United Nations Office of Drugs and Crime. (2015). Use of drugs in 2013 (or latest year available). Obtained from UNODC: http://www.unodc.org/wdr2015/interactive-map.html

The increase in use of this substance is due in part to more and more countries legalizing the use and growing of recreational or medicinal marijuana.  In some countries, like Spain, the use of cannabis has been decriminalized, so marijuana users are not looked down upon socially. 

The figure below shows the current legal status for marijuana worldwide:

marijuana in the world

Source: By Trinitresque (Own work) [CC BY-SA 3.0], from Wikimedia Commons

There is an intense debate about whether or not marijuana should be legal, and although I have a clear position on the issue, I prefer to keep it to myself and give only the facts so that everyone can decide for themselves. 

10 Effects and Consequences of Marijuana

The following list of facts is intended especially for people who use marijuana, or are considering using marijuana, although I believe that this information of interest for many and could be useful to anyone who wants to form an opinion about marijuana that has a solid foundation and is based on facts.

  1. It affects your brain in the short term. As previously explained, the active ingredient in marijuana (THC) binds to cannabinoid receptors, which triggers the release of dopamine from the reward system.  All substances, actions, objects, etc. that can be the object of an addiction cause this effect. 
  2. It causes psychological addiction. Because of the release of dopamine in the reward system, a pleasant effect is created that reinforces and makes the user want to continue using it. 
  3. It doesn’t produce brain changes in the long term. Unlike other drugs, like heroin or cocaine, it does not cause long-term changes to the brain.  This means that the brain changes described in point 1 are temporary. 
  4. It does not cause physiological addiction. Physiological addiction occurs when the prolonged use of a substance creates permanent changes in the brain that cause feelings of discomfort when the person stops using the substance for a period of time (withdrawal).  Marijuana does not cause this type of addiction, since it doesn’t cause long-term brain changes, so people who use this substance do so to obtain the positive effects, not to mitigate the negative effects of using it. 
  5. Continuous and prolonged use can cause unwanted effects in behavior. Although it doesn’t cause long-term effects on the brain, the brain changes that it does cause last for a period of time (about 2 hours).  Therefore, if someone consumes marijuana frequently, the brain doesn’t have time to recover between uses.  This is what happens with some chronic users of large quantities, because their brains do not recover and an amotivational syndrome results.  This syndrome is characterized by a loss of interest and motivation to do anything, including hobbies or things that the person previously enjoyed. 
  6. It causes a tolerance. The brain becomes used to the changes caused by marijuana and increasingly higher doses of the substance are needed for the person to feel the same effects, so they increase the dose and frequency, possibly becoming a chronic user.  
  7. Its main effect is stimulating and sedative. In addition to other effects, a low dose can cause euphoria, reduction of certain types of pain (for example, eye pain), reduced anxiety, increased sensitivity to color and sound, reduced short-term memory (recent memories), slowing of body movements, stimulation of appetite and thirst, and loss of time awareness.  High doses can cause panic, delirium, and psychosis. 
  8. It can promote the development of some diseases associated with use through smoking. Consuming marijuana by smoking it mixed with tobacco promotes the development of diseases related to the use of tobacco, such as respiratory and cardiovascular diseases
  9. In can induce schizophrenia if use begins during adolescence. In a study using rats conducted by Dr. Kuei Tseng found that use in adolescent rats caused a deficit in the maturation of GABAergic connections between the ventral hippocampus and the prefrontal cortex, which causes reduced impulse control. This deficit in maturation is also found in patients with schizophrenia, but it is not the only cause for developing of the disease.  To develop schizophrenia, it is necessary to have a genetic predisposition and to live in a certain environment.  For this reason, the simple fact of smoking marijuana during adolescence cannot cause schizophrenia, but it can induce it in people with genetic predisposition and it can increase the probabilities of experiencing it. 
  10. It can be used as a therapeutic agent. Cannabis possesses many therapeutic properties, including anxiolytic, sedative, relaxing, analgesic and anti-depressive properties.  It is recommended in low doses for many diseases that cause pain and anxiety, such as multiple sclerosis, fibromyalgia, chronic pain, and some types of cancer. 


Please enter your comment!
Please enter your name here