Marijuana (Cannabis)

What is marijuana?

Marijuana is a general term used for the dried leafs of plant cannabis. This plant has two main types of Indica and Sativa. Scientists has created a third type called Hybrid which is a breed of the Indica and Sativa plants.

The chemical in marijuana that causes the high (and many of its other effects) is delta-9 tetrahydrocannabinol, or THC. But there are over 400 other cannabinoid chemicals in the plant; CBD is one of those. Different cannabinoids can have very different biological effects; CBD, for example, does not make people high and is not intoxicating. And, there is reason to believe it may have a range of medicinal uses, including in the treatment of neuropathic pain, anxiety, insomnia and nausea.

Most cannabinoids (including THC) interact with specific targets on cells in the body, the CB1 and CB2 receptors. CB1 receptors are found mainly in the brain and are important for learning, coordination, sleep, pain, brain development, and other functions; CB2 receptors are found mostly in the immune system. CBD has very little effect on CB1 and CB2 receptors. This is probably why it does not make people high and is not mind-altering; in fact it may even blunt some of THC’s psychotropic effects. Most marijuana grown for recreational use is very low in CBD content (and high in THC). CBD’s actions in the body are not well understood, but they appear to involve several signaling systems besides the CB receptors, including a serotonin receptor.

The fact that chemicals in marijuana can speak the body’s chemical language (and cause both beneficial and harmful effects) is not surprising and does not make marijuana special. Many plants, including the opium poppy, tobacco, and coca are similar in that regard. Extracting and amplifying the medicinal benefits of such plants and minimizing their potential harms can lead the way to effective medications, but are also a major scientific challenge.

How common is marijuana use?

  • Marijuana is the most common illicit drug in the United States.
  • According to the 2014 estimates from the United States National Survey on Drug Use and Health (NSDUH) 35 million persons aged 12 or older (13.2%) used cannabis in the past year.
  • These numbers were increased by 9.7 millions (2.6%) since 2004.
  • 15% or 1 in 7 of marijuana users were found to meet criteria for Cannabis Use Disorder.
  • Between 2004 and 2011, the emergency department visit rate increased from 51 to 73 visits per 100,000 population aged 12 or older, for cannabis-only use. Adolescents aged 12-17 years showed the largest increase in the cannabis-only involved emergency visit rate.

According to a study by The World Health Organization, the past-30-day cannabis use among youth aged 15 across 40 countries, 13% of Canadian youth reported using cannabis the past-30-days. This number was only surpassed France where 15% of you reported using cannabis the past-30-days. (World Health Organization, 2014).

What are the risk factors for using cannabis and cannabis products?

A recent large scale international population based study found genetic predisposition to marijuana and cannabis products use. The same study also found that some of the same genes associated with the use of cannabis are also associated with certain personality types and psychiatric conditions. The study identified 35 genes associated with cannabis use. The strongest association was with the gene CADM2 which has been found to be associated with risky behaviour, personality and alcohol use. According to this study this gen explains approximately 11 percent of the differences in cannabis use between people. Another interesting finding of this study was the genetic overlap between cannabis use and the risk of schizophrenia. This study found that people with vulnerability to develop schizophrenia were at increased risk of using cannabis.

Why do people use marijuana products?

People use marijuana and marijuana products for reasons such as:

  1. Relaxation
  2. Reduce muscle spasm in MS patients
  3. Reduced some types of pain
  4. Improved sleep
  5. Increase appetite
  6. Gaining weight
  7. Reduce nausea in cancer patients and individuals severely ill

What are the health effects of marijuana/cannabis?

Researcher have found that youth are unclear on the effects and harms of cannabis use , which could put them at an increased risk for use. This fact is concerning as brain development can be compromised by frequent cannabis use initiated in early adolescence.

Because marijuana impairs short-term memory and judgment and distorts perception, it can impair performance in school or at work and make it dangerous to drive. It also affects brain systems that are still maturing through young adulthood, so regular use by teens may have negative and long-lasting effects on their cognitive development, putting them at a competitive disadvantage and possibly interfering with their well-being in other ways. Also, contrary to popular belief, marijuana can be addictive, and its use during adolescence may make other forms of problem use or addiction more likely.

In a recent NIDA-supported study, males from low-income backgrounds who used marijuana in escalating frequency throughout their teen years exhibited disrupted connectivity at age 20 in a brain circuit that links rewarding experiences with motivation and mood. The study also found that disruption in the circuit at age 20 was associated with lower educational achievement and higher risk for depression at age 22. Some of the most common health effects of marijuana use include:

  • disorientation
  • altered time and space perception
  • lack of concentration
  • impaired learning and memory
  • alterations in thought formation and expression
  • drowsiness
  • sedation
  • mood changes
  • paranoia
  • fluctuating emotions
  • flights of fragmentary thoughts with disturbed associations
  • image distortion
  • psychosis
  • increased heart rate
  • reddening of the eyes
  • dry mouth and throat
  • increased appetite
  • memory and learning
  • difficultly in thinking and problem-solving
  • loss of coordination
  • Heavy users may have increased difficulty sustaining attention
  • sensory functions are not highly impaired, but perceptual functions are significantly affected.
  • The ability to concentrate and maintain attention are decreased during marijuana use, and impairment of hand-eye coordination is dose-related over a wide range of dosages.
  • Impairment in retention time and tracking, subjective sleepiness, distortion of time and distance, vigilance, and loss of coordination in divided attention tasks have been reported.
  • fatigue
  • urinary retention
  • constipation
  • decreased motor coordination
  • lethargy
  • slurred speech
  • dizziness
  • lung damage
  • daily cough and phlegm, symptoms of chronic bronchitis
  • Heavy and long-term marijuana smoking damages lung tissues. It is well established that marijuana burns  16 times hotter than tobacco. Also, it produced twice as many as carcinogens as tobacco. Clinical studies has found higher risk of bronchitis, emphysema, and cancer among marijuana-only smokers compared with non-smokers
  • Motor vehicle accident
  • Work-place accidents
  • Job loss
  • dependence
  • Euphoria
  • hallucinations
  • Impaired immune system
  • Lack of ambition
  • Apathy

What are the social impact of Marijuana use on individuals?

Researchers used the National Education Longitudinal Study to estimate the association between illicit drug use during high school and the number of years of schooling completed. Findings of this study suggest that marijuana use and cocaine use in high school are associated with reductions in the number of years of schooling completed. (Chatterji P, 2006)

What are the available forms of marijuana?


  • Nabilon (Cesamet)
  • Dronabinol (Marinol)


  • Sativex Spray
  • Hasish
  • Oil
  • Tincture

Which medical conditions can be treated with marijuana?

Over the past two to three decades there has been a surge in the claims for beneficial effects of marijuana use.

Scientific evidence has confirmed that cannabis and cannabis extracts can be effective treatment for treatment of:

  1. Muscle spasticity in MS patients (CBD)
  2. Anxiety (CBD)
  3. Poor sleep (CBD)
  4. Seizure (only specific conditions)
  5. Nausea in cancer patients

Currently, there is a lack of evidence for use of cannabis and cannabis extracts for treatment of:

  1. Migraine headache
  2. Depression
  3. Cancer
  4. Infections
  5. Fibromyalgia and chronic fatigue
  6. Arthritis

How is marijuana metabolized in body?

THC Plasma concentrations decrease rapidly after the end of smoking due to rapid distribution into tissues and metabolism in the liver. THC is highly lipophilic and initially taken up by tissues that are highly perfused, such as the lung, heart, brain, and liver. This requires an individual to smoke one joint every 2 hours to achieve constant pleasure effect from marijuana. Because of high lipid solubility of cannabinoids, urine drug screen detects positive for days up to 4 weeks after last use of marijuana among daily smokers.

Is marijuana (cannabis, Hash) addictive?

  • It is reported that 9% of individuals who use marijuana regularly, develop dependence to it.
  • Withdrawal from regular MJ use does occur. A typical MJ detox in a heavy user will last 3 to 5 days and may include irritability, insomnia, anxiety, headache, nausea and vomiting, and sometimes diarrhea. Patients should drink plenty of fluids and plan to be out of commission for a while. You can provide anti-emetics and analgesics to smooth out the process.
  • We have no medications for treating marijuana use disorder. Dronabinol (Marinol) is a synthetic form of THC that is FDA approved for intractable nausea and AIDS wasting syndrome, but clinical trials have not shown it to be effective for substitution treatment of MJ abuse.

Is marijuana potency associated with dependence?

Researchers used data from the Michigan Longitudinal Study to determine whether higher average potency levels at initiation of cannabis use were associated with cannabis use disorder (CUD). Their findings indicate that the average potency of cannabis (%THC) increased from 4% to 12% between 1994 and 2012. After adjusting for gender, regular marijuana use, and birth year, they found that potency was associated with progression to first cannabis use disorder (HR= 1.4). Findings of this study indicate that for every 1% increase in cannabis potency, there was a 1.4 times increased risk of progression to onset of CUD symptoms. Progression to first CUD symptoms was associated with regular cannabis use (HR, 4.1) and daily cannabis use (HR, 3.14). Researchers in this study concluded that cannabis potency may be associated with CUD symptom progression. (Arterberry BJ 2019)

What drug interactions has been reported with marijuana?

Cocaine and amphetamines may lead to increased hypertension, tachycardia and possible cardiotoxicity. Benzodiazepines, barbiturates, ethanol, opioids, antihistamines, muscle relaxants and other CNS depressants increase drowsiness and CNS depression. When taken concurrently with alcohol, marijuana is more likely to be a traffic safety risk factor than when consumed alone.

When and who should not use marijuana and marijuana products?

Using cannabis products with psychiatry medications could affect their blood level and metabolism which could result in intoxication with those medications. Ask your pharmacy or doctor about such interactions.

Is it safe to use marijuana during pregnancy or breastfeeding?

Recent clinical studies have found that THC can remain in breast milk for up to six days after use. This findings is of concern for mothers who smoke pot during breastfeeding.

Use of cannabis products during pregnancy and breastfeeding has been linked to small baby size and poor mental and physical development later in life.


Cannabis use can affect individuals’ cognitive function. Avoid using cannabis products before driving or working with machinery.


This document is prepared by the “Mental Health for All” team. This document is provided for information purposes only and does not necessarily represent endorsement by or an official position of the Essentials of Medicine. Advice on the treatment or care of an individual patient should be obtained through consultation with a physician who has examined that patient or is familiar with that patient’s medical history.


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