Negative Effects of Marijuana & THC

Despite some contentious discussions regarding the addictiveness of marijuana, the evidence clearly indicates that long-term marijuana use can lead to addiction.
— – Volkow, N., Baler R., Compton, W., & Weiss, S. (2014, June 5). Adverse health effects of marijuana use. New England Journal of Medicine.
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The subject of marijuana’s legality is one that causes heated debate about people’s “right” to smoke or otherwise ingest cannabis.  Anytime  “rights” come into a discussion, emotions tend to run high, and because of this, science often takes a back seat.  

But for many doctors, researchers, and scientists who have studied the effects of marijuana, it’s impossible to just focus on rights. To do so is to ignore the evidence.  And unfortunately for those eager to prove marijuana’s “harmlessness,” the evidence shows an abundance of both short-term and long-term negative effects, especially among adolescents and long-term or heavy users.   

Short-term negative effects of marijuana & THC

THC & Marijuana can cause impaired memory/cognitive functioning

  • Studies have shown that marijuana will not destroy memories you already have but can prevent you from forming new memories.
  • “Since marijuana use impairs critical cognitive functions, both during acute intoxication and for days after use, many students could be functioning at a cognitive level that is below their natural capability for considerable periods of time.” (Volkow, et al).

THC & Marijuana can cause disrupted motor control

  • The greatest concentration of cannabinoid receptors resides in the parts of the brain that are responsible for movement coordination. This results in a lowered reaction time.
  • The article quote above (Volkow, et al) references an accident culpability analysis in which people testing positive for THC were “3 to 7 times as likely to be responsible for a motor-vehicle accident as persons who had not used drugs or alcohol before driving.”

Physical and mental health risks of Marijuana & THC

  • According to the National Institute of Health (NIH), “Marijuana raises heart rate for up to 3 hours after smoking.”
  • “Use of marijuana may result in intense anxiety, panic attacks, or paranoia.” (NIH)

Long-term negative effects of marijuana of THC

THC & marijuana can cause alterations in brain development

  • Research suggests that regular use of marijuana can have negative effects on the brain, particularly in adolescence, as it is especially malleable from birth to age 21.
  • “As compared with unexposed controls, adults who smoked marijuana regularly during adolescence have impaired neural connectivity (fewer fibers) in specific brain regions.” (Volkow, et al)
  • According to an article in Psychology Today (“Long term effects of marijuana on the brain,” by Joshua Gowin, Ph.D.), a study comparing the brains of marijuana smokers who began in adolescence and a comparison group who never smoked, found that “the neural connections between the brain’s left and right hemispheres were impaired in the marijuana users relative to the non-users, which could mean that smokers’ brains have poorer internal communication.”

THC & marijuana can cause apathy, drowsiness, lack of motivation

  • Studies have shown that regular and adolescent marijuana use destroys dopamine, the chemical in the brain that produces a person’s “get up and go.”
  • Low dopamine causes lethargy and lack of motivation, which can lead to poor school performance and lower lifetime achievement.  
  • A decrease in dopamine also causes depression and a diminished capacity for expressing feelings of joy and excitement.  

THC & marijuana can cause physical and mental health risks

  • Marijuana smoke irritates the lungs and reduces a person’s resistance to ordinary illnesses, such as colds. Chronic bronchitis and lung infections are common in heavy users.
  • “Marijuana is also linked with psychoses (including those associated with schizophrenia), especially among people with a pre-existing genetic vulnerability, and exacerbates the course of illness in patients with schizophrenia.” (Volkow, et al)

THC & Marijuana have a risk of addiction

  • A study done by the National Epidemiologic Survey on Alcohol and Related Conditions in 2011 found that 1 in 10 people who use marijuana eventually become addicted to it.
  • The number goes up to 1 in 6 among marijuana users who start as adolescents.
  • 25-50% of daily marijuana users become addicted to it.
  • “As compared with persons who begin to use marijuana in adulthood, those who begin in adolescence are approximately 2 to 4 times as likely to have symptoms of cannabis dependence within 2 years after first use.” (Volkow, et al)
  • Regular marijuana users who stop using often experience withdrawal symptoms, including: irritability, trouble sleeping, unease/dissatisfaction, craving, and anxiety.

The science behind the negative effects of Marijuana & THC is real

In different parts of the country or the world, you may or may not have the “right” to smoke marijuana.  But whether you are smoking it legally does not change the negative effects the regular use of cannabis has on your body, your brain, your health, or your mood.  The science behind these effects is real, no matter where in the world you are when you smoke or buy your weed.

If you continue to smoke marijuana despite the negative effects it has on you and your life, there’s a chance you are already addicted.   If this is the case, please seek help. You don’t have face it alone.