Cannabis
What is it?
The word “cannabis” refers to all products derived from the plant Cannabis sativa.
The cannabis plant contains about 540 chemical substances.
Mind-altering psychoactive drug. In the form of marijuana: Dry, shredded, green/brown mix of flowers, stems, seeds and leaves from the cannabis sativa plant. THC (delta-9-tetrahydrocannabinol) is the main ingredient that produces the psychoactive effect. Addictive.
Besides THC and CBD, more than 100 other cannabinoids have been identified.
Alternative Names
Aunt Mary, BC Bud, Chronic, Dope, Gangster, Ganja, Grass, Hash, Herb, Joint, Mary Jane, Mota, Pot, Reefer, Sinsemilla, Skunk, Smoke, Weed, Yerba,
Legality
Common Forms
Greenish-gray mixture of dried, shredded leaves, stems, seeds, and/or flowers; resin (hashish) or sticky, black liquid (hash oil)
Epidiolex, which contains a purified form of CBD derived from cannabis, was approved for the treatment of seizures associated with Lennox-Gastaut syndrome or Dravet syndrome, two rare and severe forms of epilepsy.
Marinol and Syndros, which contain dronabinol (synthetic THC), and Cesamet, which contains nabilone (a synthetic substance similar to THC), are approved by the FDA. Dronabinol and nabilone are used to treat nausea and vomiting caused by cancer chemotherapy. Dronabinol is also used to treat loss of appetite and weight loss in people with HIV/AIDS.
Common Ways Taken
Smoked, Vaped, Eaten (mixed in food or brewed as tea)
Short Term Effects
Enhanced sensory perception and euphoria followed by drowsiness/relaxation; slowed reaction time; problems with balance and coordination; increased heart rate and appetite; problems with learning and memory; anxiety.
Long Term Effects
Mental health problems, chronic cough, frequent respiratory infections.
Other Health-related Issues
THC vaping products mixed with the filler Vitamin E acetate (and possibly other chemicals) has led to serious lung illnesses and deaths. Pregnancy: babies born with problems with attention, memory, and problem solving.
When Combined With Alcohol
Increased heart rate, blood pressure; further slowing of mental processing and reaction time.
Withdrawal Symptoms
Irritability, trouble sleeping, decreased appetite, anxiety.
Source: National Institutes of Health (Collected 2023)
Additional Information
Some people who use marijuana will develop marijuana use disorder, meaning that they are unable to stop using marijuana even though it’s causing health and social problems in their lives.
- One study estimated that approximately 3 in 10 people who use marijuana have marijuana use disorder.
- Another study estimated that people who use cannabis have about a 10% likelihood of becoming addicted.
- The risk of developing marijuana use disorder is greater in people who start using marijuana during youth or adolescence and who use marijuana more frequently.
The following are signs of marijuana use disorder:
- Using more marijuana than intended
- Trying but failing to quit using marijuana
- Spending a lot of time using marijuana
- Craving marijuana
- Using marijuana even though it causes problems at home, school, or work
- Continuing to use marijuana despite social or relationship problems.
- Giving up important activities with friends and family in favor of using marijuana.
- Using marijuana in high-risk situations, such as while driving a car.
- Continuing to use marijuana despite physical or psychological problems.
- Needing to use more marijuana to get the same high.
- Experiencing withdrawal symptoms when stopping marijuana use.
People who have marijuana use disorder may also be at a higher risk of other negative consequences, such as problems with attention, memory, and learning.
Some people who have marijuana use disorder may need to use more and more marijuana or greater concentrations of marijuana over time to experience a “high.” The greater the amount of tetrahydrocannabinol (THC) in marijuana (in other words, the concentration or strength), the stronger the effects the marijuana may have on the brain. The amount of THC in marijuana has increased over the past few decades.
In a study of cannabis research samples over time, the average delta-9 THC (the main form of THC in the cannabis plant) concentration almost doubled, from 9% in 2008 to 17% in 2017.7 Products from dispensaries often offer much higher concentrations than seen in this study. In a study of products available in online dispensaries in 3 states with legal non-medical adult marijuana use, the average THC concentration was 22%, with a range of 0% to 45%.8 In addition, some methods of using marijuana (for example, dabbing and vaping concentrates) may deliver very high levels of THC to the user.
Researchers do not yet know the full extent of the consequences when the body and brain are exposed to high concentrations of THC or how recent increases in concentrations affect the risk of someone developing marijuana use disorder.
Is Cannabis Helpful In Treating Health Condiditons?
Pain
A 2018 review looked at 47 studies (4,743 participants) of cannabis or cannabinoids for various types of chronic pain other than cancer pain and found evidence of a small benefit. Twenty-nine percent of people taking cannabis/cannabinoids had a 30 percent reduction in their pain whereas 26 percent of those taking a placebo (an inactive substance) did. The difference may be too small to be meaningful to patients. Adverse events (side effects) were more common among people taking cannabis/cannabinoids than those taking placebos.
A 2015 review of 28 studies (2,454 participants) of cannabinoids in which chronic pain was assessed found the studies generally showed improvements in pain measures in people taking cannabinoids, but these did not reach statistical significance in most of the studies. However, the average number of patients who reported at least a 30 percent reduction in pain was greater with cannabinoids than with placebo.
Helping To Decrease Opioid Use
A 2017 review looked at studies in people in which cannabinoids were administered along with opioids to treat pain. These studies were designed to determine whether cannabinoids could make it possible to control pain with smaller amounts of opioids. There were 9 studies (750 total participants), of which 3 (642 participants) used a high-quality study design in which participants were randomly assigned to receive cannabinoids or a placebo. The results were inconsistent, and none of the high-quality studies indicated that cannabinoids could lead to decreased opioid use.
Data from a national survey (not limited to people on Medicare) showed that users of medical marijuana were more likely than nonusers to report taking prescription drugs.
An analysis of data from 1999 to 2010 indicated that states with medical marijuana laws had lower death rates from overdoses of opioid pain medicines, but when a similar analysis was extended through 2017, it showed higher death rates from this kind of overdose.
Anxiety
A small amount of evidence from studies in people suggests that cannabis or cannabinoids might help to reduce anxiety. One study of 24 people with social anxiety disorder found that they had less anxiety in a simulated public speaking test after taking CBD than after taking a placebo.
Epilepsy
Cannabinoids, primarily CBD, have been studied for the treatment of seizures associated with forms of epilepsy that are difficult to control with other medicines. Epidiolex (oral CBD) has been approved by the FDA for the treatment of seizures associated with two epileptic encephalopathies: Lennox-Gastaut syndrome and Dravet syndrome. (Epileptic encephalopathies are a group of seizure disorders that start in childhood and involve frequent seizures along with severe impairments in cognitive development.) Not enough research has been done on cannabinoids for other, more common forms of epilepsy to allow conclusions to be reached about whether they’re helpful for these conditions.
Glaucoma
Studies conducted in the 1970s and 1980s showed that cannabis or substances derived from it could lower pressure in the eye, but not as effectively as treatments already in use. One limitation of cannabis-based products is that they only affect pressure in the eye for a short period of time.
A recent animal study showed that CBD, applied directly to the eye, may cause an undesirable increase in pressure in the eye.
HIV/AIDS Symptoms
Unintentional weight loss can be a problem for people with HIV/AIDS. In 1992, the FDA approved the cannabinoid dronabinol for the treatment of loss of appetite associated with weight loss in people with HIV/AIDS. This approval was based primarily on a study of 139 people that assessed effects of dronabinol on appetite and weight changes.
There have been a few other studies of cannabis or cannabinoids for appetite and weight loss in people with HIV/AIDS, but they were short and only included small numbers of people, and their results may have been biased. Overall, the evidence that cannabis/cannabinoids are beneficial in people with HIV/AIDS is limited.
Inflammatory Bowel Disease
A 2018 review looked at 3 studies (93 total participants) that compared smoked cannabis or cannabis oil with placebos in people with active Crohn’s disease. There was no difference between the cannabis/cannabis oil and placebo groups in clinical remission of the disease. Some people using cannabis or cannabis oil had improvements in symptoms, but some had undesirable side effects. It was uncertain whether the potential benefits of cannabis or cannabis oil were greater than the potential harms.
A 2018 review examined 2 studies (92 participants) that compared smoked cannabis or CBD capsules with placebos in people with active ulcerative colitis. In the CBD study, there was no difference between the two groups in clinical remission, but the people taking CBD had more side effects. In the smoked cannabis study, a measure of disease activity was lower after 8 weeks in the cannabis group; no information on side effects was reported.
Irritable Bowel Syndrome
Although there’s interest in using cannabis/cannabinoids for symptoms of IBS, there’s been little research on their use for this condition in people. Therefore, it’s unknown whether cannabis or cannabinoids can be helpful.
Movement Disorders Due to Tourette Syndrome
A 2015 review of 2 small placebo-controlled studies with 36 participants suggested that synthetic THC capsules may be associated with a significant improvement in tic severity in patients with Tourette syndrome.
Multiple Sclerosis
A review of 17 studies of a variety of cannabinoid preparations with 3,161 total participants indicated that cannabinoids caused a small improvement in spasticity (as assessed by the patient), pain, and bladder problems in people with multiple sclerosis, but cannabinoids didn’t significantly improve spasticity when measured by objective tests.
A review of 6 placebo-controlled clinical trials with 1,134 total participants concluded that cannabinoids (nabiximols, dronabinol, and THC/CBD) were associated with a greater average improvement on the Ashworth scale for spasticity in multiple sclerosis patients compared with placebo, although this did not reach statistical significance.
Evidence-based guidelines issued in 2014 by the American Academy of Neurology concluded that nabiximols is probably effective for improving subjective spasticity symptoms, probably ineffective for reducing objective spasticity measures or bladder incontinence, and possibly ineffective for reducing multiple sclerosis–related tremor. Based on two small studies, the guidelines concluded that the data are inadequate to evaluate the effects of smoked cannabis in people with multiple sclerosis.
A 2010 analysis of 3 studies (666 participants) of nabiximols in people with multiple sclerosis and spasticity found that nabiximols reduced subjective spasticity, usually within 3 weeks, and that about one-third of people given nabiximols as an addition to other treatment would have at least a 30 percent improvement in spasticity. Nabiximols appeared to be reasonably safe.
Nausea and Vomiting Related to Cancer Chemotherapy
A 2015 review of 23 studies (1,326 participants) on the cannabinoids dronabinol or nabilone for treating nausea and vomiting related to cancer chemotherapy found that they were more helpful than a placebo and similar in effectiveness to other medicines used for this purpose. More people had side effects such as dizziness or sleepiness, though, when taking the cannabinoid medicines.
Posttraumatic Stress Disorder (PTSD)
In one very small study (10 people), the cannabinoid nabilone was more effective than a placebo at relieving PTSD-related nightmares.
Observational studies (studies that collected data on people with PTSD who made their own choices about whether to use cannabis) haven’t provided clear evidence on whether cannabis is helpful or harmful for PTSD symptoms.
Source: National Institutes of Health (Collected 2023)
Are Cannabis and Cannabinoids Safe?
Several concerns have been raised about the safety of cannabis and cannabinoids:
- The use of cannabis has been linked to an increased risk of motor vehicle crashes.
- Smoking cannabis during pregnancy has been linked to lower birth weight.
- Some people who use cannabis develop cannabis use disorder, which has symptoms such as craving, withdrawal, lack of control, and negative effects on personal and professional responsibilities.
- Adolescents using cannabis are four to seven times more likely than adults to develop cannabis use disorder.
- Cannabis use is associated with an increased risk of injury among older adults.
- The use of cannabis, especially frequent use, has been linked to a higher risk of developing schizophrenia or other psychoses (severe mental illnesses) in people who are predisposed to these illnesses.
- Marijuana may cause orthostatic hypotension (head rush or dizziness on standing up), possibly raising danger from fainting and falls.
- The FDA has warned the public not to use vaping products that contain THC. Products of this type have been implicated in many of the reported cases of serious lung injuries linked to vaping.
- There have been many reports of unintentional consumption of cannabis or its products by children, leading to illnesses severe enough to require emergency room treatment or admission to a hospital. Among a group of people who became ill after accidental exposure to candies containing THC, the children generally had more severe symptoms than the adults and needed to stay in the hospital longer.
- Some long-term users of high doses of cannabis have developed a condition involving recurrent severe vomiting.
- There have been reports of contamination of cannabis/cannabinoid products with microorganisms, pesticides, or other substances.
- Some cannabis/cannabinoid products contain amounts of cannabinoids that differ substantially from what’s stated on their labels.
Can CBD Be Harmful?
There’s evidence that CBD may be harmful to some people.
Before the FDA approved Epidiolex (a purified CBD product) as a drug, studies were done to evaluate its effectiveness and safety. Some participants in these studies had side effects (mostly diarrhea or sleepiness), and some developed abnormalities on tests of liver function. In some instances, study participants had to discontinue Epidiolex because of liver problems. Epidiolex also interacted with some of the other drugs these people were taking.
Problems like these can be managed in patients taking Epidiolex because they’re using CBD under medical supervision. People who use CBD on their own don’t have this kind of protection. They may not even know how much CBD they’re taking. A 2017 analysis of 84 CBD products sold online found that 26 percent contained substantially less CBD than the label indicated, and 43 percent contained substantially more.
Source: National Institutes of Health (Collected 2023)