Drug Rehabilitation Blog

marijuana infographic

The Effects of Marijuana on the Body: An Infographic


Physical and Mental Effects of Marijuana

Marijuana affects the body in a number of ways, many of which are typically not a part of popular discourse on the drug. Cannabis affects neurological, psychological, and cardiovascular systems in both short and long term ways. Educating oneself to these effects allows for one to make educated decisions on one’s own, gain an awareness for when someone else is under the influence of marijuana, and understand and begin to address when someone close may have a marijuana dependency issue.

Through mass culture and popularly disseminated anecdotal evidence, most of us are aware, to a certain extent, of some of the effects of marijuana. Some of the effects many of us are probably aware of are red eyes, dry mouth, euphoria (laughter, positive effect, feeling great), increased appetite, and lethargy, as well as possible anxiety.

These are generally true. One study suggested noted that caloric intake increased 40% in subjects who smoked marijuana. Marijuana indeed does seem to elicit negative effect in certain users and the active component of marijuana is considered to be anxiogenic or anxiety-producing. Still, a more comprehensive list should be offered up here.

Acute or Short-Term Effects

The psychoactive chemical of marijuana, delta9-tetrahydrocannabinol (Δ9-THC or just THC), reacts with cannabinoid receptors in the brain and causes various effects. The acute effects of marijuana (THC and other associated cannabinoids) include:

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  • Euphoria
  • Dry mouth
  • Reddening of eyes
  • Decrease in intra-ocular pressure
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  • Muscle relaxation
  • Depersonalization
  • Increased appetite
  • Effects on attention
  • Altered visuospatial reasoning
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  • Altered time sense
  • Lethargy
  • Drowsiness
  • Occasional anxiety and paranoia
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So, what does this mean in practice? Number one, marijuana impairs reaction time. One study noted that drivers under the influence of marijuana had an increase in brake latency. That is to say, drivers typically could not stop as quickly as they would be able to otherwise. Perhaps, unsurprisingly, according to that same study, marijuana is frequently found in the blood of drivers involved in auto accidents. We can, therefore, glean that motor impairment and increased reaction time, as an acute effect of marijuana, should not be trifled with.

Number two, as for “depersonalization,” marijuana has marked  effects that, in certain susceptible people, may predicate episodes of mental illness. A study from The American Journal on Addictions notes case studies that indicate a causal link between marijuana use and the onset of symptoms of mood disorders and/or schizophrenia-related disorders in adolescents. Marijuana is an anxiogenic substance; its associated neurotransmitter anandamide also affects norepinephrine levels, a neurotransmitter linked with the “flight or fight” response related to anxiety. As such, this anxiety, along with the cognitive changes associated with marijuana use, can result in terrifying and psychologically damaging experiences for certain users. While one would be amiss by saying that marijuana leads to mental illness in general, in certain risk-associated populations, evidence indicates that its use can prompt some unsettling effects. People with a family history of mental or mood disorders, emotional instability, and known psychosocial issues are at risk of negative consequences from marijuana. But even then, one is often at the whim of one’s own brain chemistry, which is largely a mystery to most of us.

People with a family history of mental or mood disorders, emotional instability, and known psychosocial issues are at risk of negative consequences from marijuana.

So, how else does marijuana affect the body? Acute marijuana intake via smoking has cardiovascular effects. The characteristic blood shot eyes of the marijuana user result from the congestion of blood vessels for example. Given this particular somatic effect, perhaps it is not surprising then that other cardiovascular effects such as increased heart rate and a slight increase in supine (lying down) blood pressure, as well as occasional, but marked, orthostatic hypotension (dizzy spells), also result from marijuana use. These types of somatic effects can be (another) cause for anxiety in certain users, especially given the sensitivity to stimuli associated with THC. In rare cases, infarction (heart-attack), stroke, and other cardiovascular problems have been reported. But even in these rare instances, this type of reaction typically only occurs in long-term smokers of marijuana.

Long-Term Effects of Marijuana Use

Now, part of the problem with discussing long-term effects of marijuana on the body is that the results and opinions on the matter are somewhat contested. The following is a list of possible long-term side effects. An asterisk next to the side indicates that the effect listed is an object of debate amongst researchers.

Long-term effects of marijuana smoking:

  • Respiratory and cardiovascular problems
  • Possible link to effects on memory and intelligence*
    • Short term*
    • IQ*
    • Possible link to depression and other issues*
      • Unipolar depression*
      • Bipolar disorder*
      • Schizophrenia or related disorders*

While most studies indicate that there is probably little connection to marijuana use and cancer, the vaporization of marijuana into the lungs over a long-term period still results in respiratory problems. A study by the Canadian Medical Association concluded that, even independent of tobacco use, marijuana use does indeed lead to higher chance of developing chronic obstructive lung disease.


Memory, Intelligence, and Marijuana Use

Studies, however, are less conclusive about issues regarding memory and intelligence. However, what we can say somewhat conclusively is that long-term marijuana use, being chronically in a neurochemically altered state of mind, results in activation of parts of the brain that are not normally used for visuospatial memory tasks. A study from Psychopharmacology notes “ this compensation [by the brain] may not be sufficient in more real-life situations where this type of processing is required and thus, deficits may be observed.” In other words, marijuana usage does have real, observable effects on how its users see, judge, and react to various stimuli; these changes in processing may or may not be compatible with uncontrolled and unfamiliar environments. Marijuana is not a substance whose long-term effects should be devalued or ignored even if more research needs to be done to figure out exactly what those effects are.
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Effects of Marijuana

As far as mental disorders and marijuana, again, this has been a subject of debate amongst researchers for some time. The problem here is one of causality. We do know, as noted above, that for people with certain risk factors for mental disorders, marijuana use may indeed prompt some symptoms of a mental disorder. However, to say that marijuana causes these disorders would be a misstep. More to the point, people with mental disorders may use marijuana to combat symptoms of their illness, rather than marijuana directly causing the illness itself (though its use may exacerbate symptoms).  Still, given marijuana’s demonstrable effects in brain chemistry, excessive and chronic use should not be something to slough off; certain long-term effects just aren’t known yet.

The Overall Impact of Long-Term Marijuana Use

In conclusion, the short and long-term effects go beyond the common associations of excessive laughter, the “munchies” and a generally torpid effect. Marijuana and its psychoactive component, THC, have far-reaching cardiovascular, psychological, and neurological effects. Beyond this, marijuana has a marked and observable long-term effect on brain chemistry and deleterious effects on the respiratory system. Knowing these facts will help people make informed decisions, as well as bring awareness of how others are being affected by marijuana.

Marijuana use is often linked to other drug use, as well. You can learn about the effects of heroin, crack, and bath salts here on our site today.


  • Ty

    Is this information actually believed?Must be by anyone with a brain capacity of a 9 year old because almost 70 percent of the drivel spewed in thia article, is completely an attempt at signing more potential clients/patients for the boundless rehabilitation centers across this Patetic Nation!

  • Diane C

    Marijuana has long been looked at as a sort of safe drug. One that doesn’t have bad effects on the person and we see now where states are starting to legalize it due to this. Even doctors are talking about the medical benefits of using it. While there may be some truth to all of this, the bottom line is that it is a drug and all drugs have some bad effects on the person. Smoking alone is bad for the body even without the other effects. If the substance you’re taking has the effect of altering your perceptions, then it isn’t good for you and shouldn’t be done.

  • Ferdo Crane

    That long term effects are confirmed with people that smoke 2 kg a day.

  • Peshov

    If it’s not for you don’t do it!

    Marijuana is not for everyone, otherwise will be legal everywhere in the world.

    It will be impossible to legalise for everyone as different people different characters and have different effects to all.

    So why bother just leave it be….;) !



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