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Marijuana Use Disorder Overview

Marijuana, also referred to as cannabis, hashish, or hash, is considered to be the most common illegal psychoactive substance in the world. The psychoactive properties are a result of the Cannabinoid delta-9-tetrahydrocannabinol (THC). The strength of marijuana is typically measured by the amount of THC concentration.

THC reaches the brain in minutes and binds to the Cannabinoid CB1 receptor in the brain. It activates these receptors in the mesolimbic dopamine system which is hypothesized to modulate positive rewarding effects.

In the 60s and 70s, marijuana strains were found to have between 0.4 and 1 percent of THC. Today cultivators have manipulated popular strains to contain up to 25 percent or more THC. The increase in potency has stirred a long and heated debate on whether or not it has triggered a rise in marijuana use disorders as well as neurological and psychological changes within the brain.

The legal status of marijuana use, including recreational and medical purposes, varies across the United States and internationally. Medical researchers suggest that around 10 percent of regular users develop marijuana use disorder, something that could be associated with cognitive impairment, mood disorders, psychosis, and problems within work, family, and social aspects of life.

Clinical Manifestations of Marijuana Use Disorder

A marijuana use disorder is is manifested by a persisting pattern of use that results in a significant life impairment in at least two domains with a 12 month period.1 These manifestations of impairment could include giving up activities that were once enjoyed, have problems at work, or developing health complications.

Unlike other substance use disorders in which the quantity and frequency of use is taken into consideration, marijuana use disorders are diagnosed through a very careful and precise assessment of impairments. Key diagnostic features that a clinician might assess include a patient denial of their use even when valid collateral sources (i.e. family, friends, work) of using exist and also denial even when there is contradicting evidence (i.e. urine testing).

Trends on the Prevalence of Marijuana Usage

The prevalence of marijuana usage varies greatly by country. For instance in countries where marijuana has been medicalized, regulated, or decriminalized, usage tends to be higher. Other usage elements that could be taken into consideration include culture and societal beliefs.

Marijuana Use in the US

The laws and attitudes toward marijuana usage in the US are becoming more relaxed. This shift in thinking has caused researchers to wonder whether or not the prevalence of using marijuana and marijuana use disorders have also changed.

The most recent published study by the National Institute on Alcohol Abuse and Alcoholism (NIAAA), suggests that things have altered in the 21st century.2 Her and her team interviewed over 36,000 American adults about their marijuana, alcohol, and drug use, as well as any psychiatric conditions.

Their goal was to present up to date nationally representative data on marijuana use and marijuana use disorders between 2012 and 2013, and to determine any changes between this year and 2002 and 2002 (the last study). The team used diagnostic criteria as found in the DSM-4.

What they found was that between 2012 and 2013, 9.5% of adults in the US had used marijuana in the past year, and 2.9% had a clinical diagnosis of DSM-4 marijuana use disorder. This meant approximately 3 out of 10 marijuana users, or 6,846,000 Americans, had a marijuana use disorder.

Furthermore, marijuana use and marijuana use disorder significantly increased since the 2001-2002 study. In fact is nearly doubled in marijuana use and the prevalence of a disorder was two-fold. No increase in the risk for developing a marijuana use disorder among users was found to be true; rather, it had decreased. The study suggested the increase in marijuana use disorder could be linked to the increase in users between the two studies.

This also corroborates with other reports of an increase in use which is likely related to changes in legislation as well as an increasing potency of THC. It is suggested that THC in marijuana could reinforce the effects; however, this needs further merit investigation.

Ultimately the concluding results of the study were that as marijuana usage continues to grow, so too could marijuana use disorders. Due to the lack of clinical understanding, public awareness is limited. This means that only a small number of people will actually seek out treatment.

Marijuana Use in the UK

Approximately one third of adults in the UK have tried marijuana; about 2.5 million people between the ages of 16 to 29 have used it in the past year. The latest drug report findings out the UK shows that marijuana was the most common drug used between 2015 and 2016, with 6.5% of adults using it in the past year. These results are similar to the previous years survey of 6.7%, but shows significant falls when compared to a decade ago (8.7%). Up to 37% of marijuana users were considered to use the drug frequently.

There is a lack of direct research on marijuana use disorders in the UK, or more frequently referred to as marijuana abuse and dependency. One relevant study that sought to provide clinicians with effective ways to assess and manage marijuana use disorders is that by psychiatrist Adam R Winstock. 3 He notes that the past decade has seen a dramatic shift in marijuana preparations in the UK.

What began with resinous hash has now migrated into high potency preparations that dominate the UK market. High-potency cannabis has been found to have soaring levels of THC and could be attributed to marijuana use disorders. Despite the large number of people who use marijuana on a regular basis, only 6% seek out treatment for abuse or dependency of marijuana.4
Furthermore, those who have been diagnosed with a marijuana use disorder do not list marijuana use as their most dominate complaint or concern. Rather respiratory problems, depression, anxiety, exacerbation of an underlying mental health disorder, inability to concentrate, and legal or employment problems reside above the actual use. The low levels of people seeking out treatment could be associated with a lack of awareness around marijuana use disorder and other harms.

How High-Potency Cannabis Affects the Brain

A new study published by researchers out of King’s College London suggest that smoking high-potency cannabis could be linked to changes in the white matter connections between the brain’s two hemispheres.5 High-potency cannabis has high levels of THC and is commonly smoked by marijuana users throughout the UK.

The brains of 56 people who sought out treatment for psychosis were scanned, in addition to a control group of 43 people. Researchers observed the density in the corpus callosum of the brain, or white matter tracts that extend outwards from neurons in one hemisphere into the other. When the white matter connections are damaged, the communication in between brain cells becomes impaired. This can lead to cognitive problems including memory loss and difficulty concentrating.

The study goes onto to suggest that there are significant links between how often a person smokes marijuana and how much damage has occurred to the white matter. People who smoked more frequently had a greater chance of white matter damage than those who did not smoke high-potency cannabis often, or who smoked less potent marijuana strains.

It should be noted that white matter damage was related to high-potency cannabis use regardless of psychosis symptoms being relevant. Researchers do not understand the cause and effect of this or how the relationship between high-potency cannabis and white matter originates. It is with hope further studies can corroborate with the current findings.

Marijuana Use in Canada

In Canada, marijuana is the most commonly used illegal drug. Currently recreational use is illegal; however, marijuana can be used for medicinal purposes when supported by a healthcare practitioner. The most recent study from 2012 reports that 10.6% of Canadians have used marijuana in the last year.6

Adolescents had the highest amount of use in 2009-2010 with 28% having smoked it at least one time. Growing research out of Canada indicates that chronic use of the drug could have adverse health effects including mental, physical, and cognitive impairment.

Another study published in 2012 shows that 21.6% of Canadians (or 6 million people) met the criteria for a substance use disorder.7 Alcohol was the most common (18.1%) with marijuana following suit, at 6.8%. This study was the first time marijuana abuse or dependency was assessed on a national level.

Marijuana Use in Australia

Marijuana use in Australia was not popular prior to the 1970s. Since this time, use has increased with the 1990s having the highest usage. It has since gradually decreased, but it continues to be the most used illegal drug in Australia. Similar to other countries, most users are in their 20s and 30s.

The Australian Institute of Health and Welfare cited daily usage of marijuana in 2004 at 16 percent, with most of these users around the age of 30-39. A 2007 study showed marijuana had been used at least once by a third of Australians over the age of 14. A further 1.6 millions people had used the drug within the last 12 months.

A 2016 household study of 115,000 people showed 48.1% of Australians has used marijuana in the last year.8 Of these people, 15.2% of females and 17.9% of males used the drug at least 300 days out of the year. Furthermore 5.9% of females and 6.9% of males reported being under the influence of marijuana for at least 12 hours a day.[^2017-study]

The Impact of Marijuana Use

Occasional use of marijuana is generally not considered to be harmful, however, when used there are notable changes in the body and mind. Overuse of the drug, or when used in conjunction with a mental health disorder, the effects could be substantial and even detrimental.

Physical Effects of Marijuana Use

Marijuana is most often smoked, but it can also be eaten, brewed into a tea, or inhaled through a special vaporizer. Regardless of how it enters the body, the nervous system, organs, and brain will be affected within minutes. (Eating it will take longer for the body to process the THC). The immediate effects can last between 3 and 4 hours and include:

  • Increase in heart rate
  • Increase in bleeding
  • Low blood pressure
  • Alteration in blood sugar levels
  • Shallow breathing
  • Dilated pupils and red eyes
  • Dry mouth and dizziness
  • Slowed reaction time

Marijuana use can also cause changes to the user’s mind and mood. Some effects may include:

  • A distorted sense of time
  • Paranoia
  • Anxiety
  • Depression

Long term effects of marijuana can vary and depend on whether or not the user is considered to have a marijuana use disorder, an issue that affects around 10-30% of people. Marijuana could worsen liver disease, low blood pressure, or diabetes. In men low testosterone, sperm count, and it’s quality may be decreased; of which could lead to a low libido and fertility.
Long term use has also been linked to mental illness in some users, such as:

  • Temporary hallucinations
  • Paranoia (Temporary or persistent)
  • Delusions
  • Psychosis
  • Worsening the symptoms of schizophrenia

It is important to note that the aforementioned is not exhaustive, and it is also not conclusive. Other studies that also consider underlying factors including THC levels and undiagnosed health issues, must be conducted.9

Addictiveness of Marijuana

Marijuana use can lead to a marijuana use disorder which takes the form of addiction. Not all users, including frequent users, will become addicted to the drug. Currently it is not understood why this holds true, but could be related to genetic predisposal, social environment, childhood, underlying health issues, and so forth.

A marijuana use disorder is associated with dependence and a withdrawal. People diagnosed with this disorder frequently report irritability, decreased appetite, cravings, restlessness, and sleep issues when they quit.10 These symptoms can last between one and two weeks or more.
Users who have been diagnosed with a marijuana use disorder, and have quit, report the process as being mildly uncomfortable. It cannot be compared to other disorders that include alcohol or prescription medications.

Many people who quit marijuana were found to have other emotional or mental issues going on, which may have been attributed to their use. In this case cognitive behavioral therapy, counseling, yoga, exercise, and meditation were all found to be very helpful. If a mental health disorder was prevalent, psychiatric help and medication may be recommended to the patient.

Impact of Marijuana Use on Quality of Life

The topic of marijuana and relationships is very controversial with some clinicians believing the two cannot go hand in hand; rather mixing like dynamite and a match. Thus, resulting in widespread, far reaching effects. Others believe marijuana has no effect on relationships, and then there are those that feel it will be inherently unique and dependent on a broad range of circumstances.

It can be said that this disorder, regardless of it being deemed mild, moderate, or severe, could minimize progress and growth in a relationship. A marijuana use disorder may impact:

  • The user’s personal life
  • Friendships
  • Intimacy
  • Commitments
  • Family life
  • Responsibilities
  • Work/school obligations

To what degree marijuana use remains casual in these associations remains an open, and broad, topic of debate that requires further research. It is entirely possible that other factors independently predispose a person to marijuana use disorders and negative life outcomes.

  1. American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) ↩
  2. Prevalence of Marijuana Use Disorders in the United States Between 2001-2002 and 2012-2013 ↩
  3. Assessment and management of cannabis use disorders in primary care ↩
  4. [2017 UK Statistics on Drug Abuse](https://digital.nhs.uk/data-and-information/publications/statistical/statistics-on-drug-misuse/2017 Statistics on Drug Misuse: England, 2017 – Report [1011.92KB]) ↩
  5. Effect of high-potency cannabis on corpus callosum microstructure ↩
  6. Marijuana Use in Canada ↩
  7. Mental and substance use disorders in Canada  ↩
  8. 2016 Household study ↩
  9. Adverse Health Effects of Marijuana Use ↩
  10. Is Marijuana Addictive ↩
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