Marijuana long-term effects?

Originally Published: October 1, 1993 - Last Updated / Reviewed On: March 14, 2014
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Dear Alice,

Does marijuana have any real, lasting effects?

Signed,
Cannabis

Dear Cannabis,

The side effects of marijuana (a.k.a. pot, weed, herb, and many other names!) use are highly debated — by both politicians and health care professionals. Marijuana use for recreational and medicinal purposes has existed for quite some time (Mayo Clinic estimates medicinal use began as early as the mid-19th century). Interestingly, the politics of marijuana use and studies related to the effects on the body and its medicinal value continue to shift and reveal a myriad of potential benefits and risks. Your question, while simple, highlights the importance of our evolving understanding of this drug.

Marijuana can enter the body in a number of ways. It can be smoked, ingested through food, inhaled through vapor, or steeped as a tea, and the way marijuana enters the body can impact the type of effects a person experiences. Smoking pot causes the substance to enter the bloodstream directly, while oral consumption is first processed in the liver. Some studies indicate that when THC is taken by mouth, a substance is then produced in the liver that can alter mood or consciousness. There are also derivatives of the plant, like delta-9-tetrahydrocannabinol (THC) and other cannabinoids (chemical components of the cannabis plant), which can be extracted and taken on their own.

Among the research that is currently available, there are mixed conclusions about the side effects associated with the use of marijuana and its various cannabinoids, including:

  • Addiction. Some research studies document that people who attempted to quit marijuana after long-term use experienced symptoms of withdrawal, including anxiety, irritability, sleeplessness, decreased appetite, and marijuana cravings. Various researchers argue that experiencing these symptoms after attempting to abstain from use of marijuana is proof that the substance can be habit forming. Other researchers counter this conclusion, stating there is not enough evidence to support a blanket claim that marijuana is addictive.
  • Appetite and reduced pain. For patients with HIV or cancer, multiple reports shows cannabinoid use can improve appetite, reduce nausea, and reduce pain.
  • Fetal development. One of the areas of agreement, amongst both supporters and opponents of marijuana use, is the negative impact on a developing fetus or a breastfeeding child. If used by a breastfeeding mother, marijuana and cannabinoids can be found in breast milk and directly passed to a breastfeeding infant.
  • Learning and memory. Recent research indicates marijuana use may cause permanent damage to areas of the brain related to memory and learning, specifically during important times of neural development (typically from when a fetus is first growing to when someone is in their early 20’s). It could even cause a significant decline in IQ. Quitting marijuana use as an adult did not seem to fully restore those losses of brain functionality. In comparison, study participants who began to smoke as adults did not experience the same mental decline.
  • Lung health. So far, there is no consensus about the connection between lung cancer and smoking pot. However, there is some speculation about how the frequency of use (i.e. heavy vs. occasional use) may impact lung cancer risk. The National Institute for Health (NIH) cautions that smoking (no matter what the substance) is still an irritant to the lungs. Marijuana smokers may experience similar respiratory symptoms to those of tobacco smokers, such as frequent cough, increased phlegm, elevated risk of lung infections, and more frequent acute chest illness.
  • Mental and emotional health. Some researchers argue that pot can help reduce anxiety, while others claim its use can exacerbate mental illness and even induce short-term psychosis, including hallucinations and paranoia. Some studies describe a wide range of potential mental and emotional side effects of marijuana (enjoyable for some and distressing for others), including confusion, inability to concentrate, sleepiness, and even feelings of exhilaration. 
  • Other physical side effects. Marijuana can cause various other physical side effects including decreased blood pressure, increased heart rate and/or heart palpitations, lightheadedness, and slower than normal reaction time.

The use of marijuana is banned by federal law, but also legalized for medicinal purposes in several states. This juxtaposition may be partially explained by the divided conclusions that exist surrounding the impact of marijuana on a person’s health. The diversity among marijuana plants and the cannabinoids found in different samples can pose a challenge to more generalizable research results. With time and additional study, hopefully more clear conclusions will surface about the benefits and risks of marijuana use.

If you have more questions or concerns about marijuana, consider checking out the Go Ask Alice! Marijuana, Hash, & Other Cannabis archive for more information. Columbia students who wish to speak with someone about their marijuana use in a non-judgmental environment can contact Counseling and Psychological Services (Morningside) or the Mental Health Service (CUMC).

Hope this helps!

Alice