Christopher J. Froehlich, Catherine J. Randall Research Scholar, University of Alabama
Alan Blum, MD, Center for the Study of Tobacco and Society, University of Alabama


Marijuana has been used both medicinally and as an intoxicant for thousands of years, notably in China. Europe and the Americas have mostly been exposed to marijuana as a medicine for about 200 years. Marijuana has progressed from an herbal medicine to a notorious illicit drug to a popular recreational drug and an alternative medicine. This change in public perception in recent years is the result of anecdotal reports on social media of its benefits. Because it is difficult for medical researchers to obtain marijuana for studies, there are insufficient data to prove or disprove many of these claims.1 One result is that medical approval of marijuana is left to state legislatures, who are “essentially legalizing recreational marijuana but forcing physicians to act as gatekeepers for those who wish to obtain it.”2

How Is Marijuana Used?

  • Marijuana as a drug (i.e. a substance intended to affect the structure or function of the body) consists of about 500 chemical compounds. The primary components are delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD).3 THC is responsible for the high that users seek.4
  • Marijuana is the most popular illicit drug in the United States. 35 million people are regular users (at least once a month).5,6
  • Around 90% of adult users describe their primary cannabis use as recreational (i.e. as a diversion).7
  • 36% of users report mixed medical and recreational marijuana usage.7
  • Users may consume marijuana in a variety of ways, such as cigarettes (joints), cigars (blunts), water pipes (bongs), vaporizers, or orally in the form of gummy bears, brownies, or other edibles.5,8
  • Marijuana is made from the flowering tops and fruits (buds, pictured below) from female cannabis plants.9 Although the most recognizable part of the plant is its leaves, these are not smoked.

Marijuana Timeline

Popular Claims

  • Marijuana can help cure cancer: Although micromolar concentrations of THC have been found to kill tumor cells, the nanomolar concentrations of THC that are more likely to be the result of recreational or medical use have been found to induce proliferation of cancer cells.10
  • Dabbing is safe: “Dabbing” involves the vaporization of concentrated butane hash oil (BHO), in which butane is used to extract THC from marijuana to produce an orange wax.11 THC concentrations in BHO vary wildly, from 4 to 30 times the concentrations found in the cannabis flower.12,13 This elevated concentration of THC in dabs can cause severe neurotoxicity and cardiotoxicity.14
  • Marijuana is not related to the development of psychotic disorders: THC produces symptoms that resemble those of psychotic disorders.15 Positive symptoms (those added onto normal behavior) include suspiciousness, paranoid and grandiose delusions, conceptual disorganization, fragmented thinking, and perceptual alterations.16 Negative symptoms (those that take away from normal behavior) include “blunted affect, reduced rapport, lack of spontaneity, psychomotor retardation, and emotional withdrawal.”15
  • There exists an association between marijuana use and psychosis that meets many but not all of the standard criteria for causality.16 It may be that marijuana use precedes the development of psychosis, or people who will develop psychosis are more likely to use marijuana, or both. Regardless of the exact sequence, there are similarities between this association and those between smoking and lung cancer, or between high sodium intake and hypertension.16
  • Marijuana can be useful for treating multiple sclerosis (MS): However, there is no way to measure spasticity, and any improvement is self reported.17 Marijuana also impairs balance and posture, exacerbating these symptoms of MS.18 It could be possible for patients to grow accustomed to this impairment and learn to counteract it.17
  • Marijuana is safe during pregnancy: Marijuana use during pregnancy is associated with an increased risk of preterm birth.19
  • Dispensaries responsibly recommend marijuana to their patrons: In a statewide cross-sectional study, 69% of Colorado dispensaries recommended cannabis to treat the morning sickness of a caller claiming to be 8 weeks pregnant. Dispensaries with medical licenses were more likely to recommend cannabis, and 36% of all dispensaries stated cannabis use during pregnancy was safe.20
  • Marijuana is safe to use with other medications: Cannabis may have drug interactions that are still unknown.19 There has been at least one probable interaction between cannabis and warfarin, resulting in gastrointestinal bleeding, nosebleeds, and increased bruising during the period of cannabis use.21
  • Marijuana is an effective treatment for glaucoma: Many states in which marijuana is approved for medical use permit it to be prescribed for glaucoma, but it is an ineffective treatment. Marijuana does lower the intraocular pressure that causes damage, but it only does so for 3-4 hours at a time. Constant treatment is required to be effective.22

Potential Medical Benefits

  • Manages Multiple Symptoms: Although marijuana is a less effective treatment of individual symptoms such as nausea, diminished appetite, and pain than other medications, it does treat these symptoms simultaneously, potentially reducing the number of medications a patient must take.23
  • Fast Antiemetic Effects: The rapid uptake of inhaled THC may prevent vomiting better than a pill, since patients may not be able to keep a pill down long enough for it to be effective.23
  • Ability to Self Titrate: Inhalation of THC also enables patients to use the minimum dosage required to manage their symptoms, reducing the risk of undesirable side effects.23
  • Epilepsy Treatment: CBD has the potential to dramatically reduce the number of seizures in various forms of epilepsy. After using Epidiolex, the first FDA approved medication derived from cannabis extracts, for 12 weeks, the median number of seizures decreased from 144 seizures per two weeks to 52 seizures per two weeks.24


Research on the medical use of marijuana remains largely inconclusive because of the inherent obstacles to studying an illegal substance. Although proof of beneficial uses of marijuana may well emerge, currently the risks outweigh the benefits.


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