What is medical marijuana?

Marijuana (also known as cannabis or marihuana) is a common name for Cannabis sativa, the hemp plant. The flowers and leaves of the plant contain a chemical known as tetrahydrocannabinol (THC), which causes most of the effects felt with marijuana use. It is the THC that is sought after for various medical applications to treat medical conditions or improve symptoms.

There are records of marijuana's use for recreational, medicinal, and religious purposes throughout history. In the late 19th century and into the 20th century, cannabis was often used in medicinal products, but its use was prohibited in Canada in the 1920s. The current culture is in favour of reestablishing the legality of cannabis, but its use remains controversial due to insufficient evidence on risk and benefits. Commercially available prescription products that use or closely imitate THC include dronabinol (Marinol®), nabilone (Cesamet®), and THC-cannabidiol (Sativex®).

What are the therapeutic uses of marijuana?

Cannabis affects the brain and the nervous systems through the endocannabinoid system. This system is involved in many physiological processes in our body such as pain sensation, mood, sleep, energy balance, and memory. Medical marijuana has been studied for several therapeutic uses, including:

  • improving quality of life in a palliative care setting (for people with terminal diseases)
  • chronic pain involving cancer
  • nausea and vomiting during chemotherapy
  • loss of appetite by cancer patients
  • neurological problems including multiple sclerosis, amyotrophic lateral sclerosis, and spinal cord injury
  • epilepsy and other seizure disorders
  • HIV/AIDS-related weight loss
  • anorexia nervosa
  • musculoskeletal disorders including osteoarthritis, rheumatoid arthritis, and fibromyalgia
  • sleep disorders
  • headache and migraine
  • movement disorders including Huntington’s disease, Parkinson’s disease, and Tourette’s syndrome
  • glaucoma
  • neuropathic pain
  • psychiatric disorders including anxiety, depression, post-traumatic stress disorder, and schizophrenia
  • asthma
  • high blood pressure
  • alcohol and opioid withdrawal symptoms
  • inflammatory skin disease such as dermatitis and psoriasis
  • irritable bowel syndrome

However, the evidence supporting therapeutic effectiveness is limiting – studies showed conflicting results and most studies were done with a small number of participants. Another issue is that the dosage used in these studies varied, making it difficult to determine the proper dosage for therapeutic use.  

What are the short-term health risks of marijuana?

Some of the short-term health risks of marijuana include:

  • change in mood
  • loss of short-term memory
  • impaired decision making ability
  • hallucinations, delusions, and paranoia
  • disorientation and confusion
  • loss of physical coordination
  • poor reaction time
  • breathing problems
  • dizziness or lightheadedness
  • low blood pressure
  • dry mouth
  • increased heart rate
  • red eyes
  • heart attack
  • stroke

What are the long-term health risks of marijuana?

Some of the long-term health risks of marijuana include:

  • chronic cough
  • greater risk of lung infection
  • increased buildup of mucus in the throat
  • increased risk of stroke
  • pregnancy complication
  • mental illness
  • loss of memory
  • decrease in intelligent quotient (IQ)
  • depression
  • anxiety
  • suicidal thoughts
  • addiction
  • cancer

Some of these side effects are more likely to affect people who start using marijuana as teenagers, as this is an important time for brain development.

Does marijuana interact with other drugs?

Marijuana may increase the risk of bleeding when used with drugs that have anticoagulating or antiplatelet effects, for example NSAIDs such as ASA (Aspirin®) and ibuprofen (Advil®, Motrin®), warfarin (Coumadin®), clopidogrel (Plavix®), heparin, and others.

Marijuana may affect the activity of liver enzymes and affect the metabolism of some drugs such as acetaminophen (Tylenol®), clarithromycin (Biaxin®), lovastatin (Mevacor®), and others.

In addition, marijuana may affect blood sugar levels and blood pressure. You should be cautious about using it if you are using any medications to treat diabetes or blood pressure. Barbiturates, estrogens, theophylline, and several other drugs also interact with marijuana. Since marijuana affects different physiological functions in the body and it may interact with medical conditions, it is important to speak to your health care professional before taking new medications.

Is marijuana addictive?

Marijuana can be addictive. It's important to know that inappropriate use of marijuana can lead to physical dependence and addiction, especially with long-term, heavy use, particularly among people who started as adolescents. Physical dependence means that when a person stops using the substance, they develop withdrawal symptoms. Medical trials have shown dependence after taking high doses of marijuana. Withdrawal symptoms typically occur 1 to 2 days after discontinuation and disappear within 1 to 2 weeks. Some of the symptoms include anger, aggression, anxiety, headache, disturbed sleep, decreased appetite, restlessness, irritability, and sweating. Physical dependence is not the same as addiction. Addiction is a psychological need for the drug that leads to cravings, inability to control drug use, and an uncontrollable need to use the drug despite the harm it may cause. Whether or not someone becomes addicted to marijuana will depend on a variety of factors, such as genetics and environmental factors.