Marijuana

Overview

Cannabis, also called weed or marijuana, is made from the dried leaves and buds of the Cannabis sativa plant. Other names for cannabis include pot or dope. But the preferred name is cannabis. The U.S. Food and Drug Administration, also called the FDA, hasn't approved the use of the cannabis plant as medicine. But many states have made it legal to use cannabis. People sometimes use cannabis to treat health conditions. This is known as medical cannabis, also called medical marijuana.

Cannabis contains chemicals called cannabinoids, which are the active compounds. There are more than 100 active compounds in cannabis. The most common cannabinoids are delta-9 tetrahydrocannabinol, also called THC, and cannabidiol, also called CBD. The THC in cannabis may change how a person thinks and feels. This change is known as a psychoactive effect. There are many other minor cannabinoids found in the plant that are being studied for medical use.

The FDA has approved three medicines that have chemicals found in cannabis. These medicines include dronabinol (Marinol) and nabilone (Cesamet). Healthcare professionals may prescribe them to help people with serious nausea and vomiting caused by medicines used to treat cancer, called chemotherapy. Some people with medical conditions that cause low appetite may take dronabinol to help them feel hungry.

The FDA also has approved a purified liquid form of cannabidiol (Epidiolex). Cannabidiol, also called CBD, is a chemical found in cannabis. Healthcare professionals prescribe this medicine to treat rare conditions that cause seizures in children, such as Lennox-Gastaut syndrome and Dravet syndrome.

Medical cannabis can be taken in many ways. It can be inhaled, taken by mouth as an edible or tincture, placed on the skin, or applied in a skin patch, also called transdermal.

People may use cannabis to treat nausea and vomiting caused by cancer treatment, appetite loss, epilepsy, chronic pain, problems sleeping and muscle spasms.

What the research says

Research on the use of marijuana for specific conditions shows:

• Glaucoma. Some studies show that cannabis lowers blood flow to the nerve that helps people see. This could raise the risk of vision changes in people with an eye disease that damages the nerve to the eyes, called glaucoma. But cannabis might lower the higher eye pressures this eye condition causes, which could be helpful. The effect doesn't seem to last more than a few hours. It likely doesn't work as well as other glaucoma treatments.
• Nausea and vomiting related to cancer treatment. Research has shown that THC helps lessen nausea and vomiting in people receiving chemotherapy. If standard medicines for nausea don't work, using THC products may help some people.
• Pain. Cannabis might lower the intensity of shooting or burning pain often due to nerve damage. This type of pain is known as neuropathic pain. People with conditions such as HIV and diabetes may have this type of pain.
• Seizures. It's not clear whether cannabis can treat seizures. Some people with conditions that cause childhood seizures, such as Lennox-Gastaut syndrome or Dravet syndrome, may take a prescription form of cannabidiol, also called CBD, by mouth to treat seizures.
• Spasticity. Cannabis may help treat muscle movements a person can't control in people with multiple sclerosis. These movements are called spasms. Most studies looked at a pill form of a chemical in cannabis, not cannabis that is smoked.
• Cancer treatment. Some people use cannabis to treat their cancers. Some studies on animals show promise. There are no large studies that show that cannabis helps treat cancer. More research is needed.

Our take

Caution

Cannabis, also called weed or marijuana, may help treat nausea that can happen while receiving chemotherapy. It also might lessen muscle spasms in people with multiple sclerosis. And it might help people with chronic pain.

But cannabis use can affect the way a person thinks and feels. People with mental health conditions may need to use it with caution. Cannabis use, even for medical reasons, isn't legal everywhere. Using it in a place where it's not allowed by law could cause legal problems.

Cannabis can be habit forming. Use of cannabis that creates problems in everyday life, such as with work, school or home, is called cannabis use disorder. People who use cannabis regularly can have withdrawal symptoms. These may include insomnia, sweating, belly pain, anger or mood changes.

Avoid using cannabis if you are pregnant or breastfeeding. Cannabis use may cause a baby to be born early or have a low weight at birth. People who are pregnant may have changes in heart rate or blood pressure due to marijuana use.

Those with active heart disease, active mental health disorders or a history of substance misuse should avoid using cannabis.

Safety and side effects

Medical cannabis, also called weed or marijuana, is generally considered safe. Most of the side effects of cannabis are due to the THC content. But different types of cannabis have different amounts of THC. This can make it very hard to know the right amount to take. The side effects seem to be worse the higher the dose of THC a person uses.

Cannabis can cause:

• Headaches.
• Dry mouth.
• Red and dry eyes.
• Dizziness and higher risk of falling.
• Drowsiness, including problems focusing.
• Fatigue.
• Coughing.
• Wheezing.

Other side effects may include:

• Nausea and vomiting.
• Feeling anxious.
• Seeing, hearing or smelling things that aren't there, known as hallucinations, and psychosis.
• Problems with memory.
• Heart that beats too fast.
• Heart that beats out of time.

Using doses of CBD higher than 300 milligrams a day can cause nausea, vomiting, diarrhea and liver conditions.

Cannabis affects how well you pay attention and move. It can affect your ability to think clearly. Don't drive or use machinery when using cannabis.

If you have a mental health condition, use cannabis with caution. If you have bipolar disorder, cannabis may make you irritable or restless with racing thoughts, also called mania. Using cannabis often might raise the risk of depression or make depression symptoms worse. Research in people who have schizophrenia suggests that cannabis use may raise the risk of losing touch with reality, also called psychosis.

Cannabis slows down messages to the brain and spinal cord, also called the central nervous system. This system is sometimes called the CNS. Using cannabis can change how you think and feel. Some people may have heart changes, such as high blood pressure. Using cannabis often for years may worsen lung conditions and may cause serious, frequent vomiting, also called cannabinoid hyperemesis syndrome.

Avoid using cannabis for two weeks before getting medicine that puts you in a sleeplike state before surgery. This medicine is called an anesthetic. Using cannabis may cause you to need more anesthetic. Using cannabis also may raise your risk of anesthesia complications, such as a very fast heart rate.

Interactions

Possible interactions include:

• Alcohol. Cannabis might make the effects of alcohol more obvious. This may include changes in mood and reaction time.
• Anticoagulant or antiplatelet medicines, herbs and supplements. These types of medicines, herbs and supplements may make you bleed more if you have a cut or injury. Using these with cannabis might raise the risk of bleeding, especially for those taking warfarin (Jantoven).
• CNS depressants. Using cannabis with medicines that lower the activity of the brain and spinal cord, called the central nervous system, might make a person sleepier and slower to respond.
• Protease inhibitors. Using cannabis may make these medicines not work as well.
• Medicines to prevent seizures. Avoid using cannabis when taking medicines to treat seizures. The medicines may not work as well or cause other side effects, such as liver conditions.

Avoid using cannabis until you review your medicines with a healthcare professional or pharmacist.