September 30, 2019

Medical cannabis and mental illness

Cannabis buds close up

Medical cannabis (also known as medical marijuana) has been explored for the treatment of various health conditions, including epilepsy, multiple sclerosis, pain management in terminally ill patients, and nausea from chemotherapy.1, 2

Now, recent studies are investigating the use of cannabidiol – a non-psychoactive cannabinoid found in the cannabis plant - to treat anxiety, depression, schizophrenia, bipolar and substance use disorders.

Therapeutic use of cannabidiol (CBD)

There is a long history of people using cannabis as medicine: the first recorded therapeutic use of cannabis was roughly 2800BC, in Emperor Shen Nung’s China.3

In ancient times, it was used to treat rheumatic pain and malaria, relieve constipation, taken with wine as anaesthesia during surgery, and for reproductive disorders.3 Similarly, in India, cannabis was used as a tranquilizer, to prevent convulsions in people with epilepsy and tetanus, and as a topical antibiotic.3

Research into the possible therapeutic uses of cannabis has advanced since then.

Since the 1970s, experts have been interested in the potential benefits of CBD as the main non-psychoactive component in cannabis.4

Research has found that CBD can produce a variety of effects. It can:

  • reduce the risk of epileptic fits
  • prevent nausea and vomiting
  • potentially replicate the effects of antidepressant and antipsychotic pharmaceuticals.4, 5

How medical cannabis works

The difference between CBD and THC

THC (delta-9-tetrahydrocannabinol) and CBD (cannabidiol) are the two of the active compounds found in the cannabis plant.6 THC is the psychoactive component which produces the ‘high’, and has also been linked to side effects such as anxiety and psychosis.7 CBD on the other hand is being researched for its ability to reduce anxiety, psychosis, nausea and seizures.7

Given these two compounds have very different effects, it is important to make the distinction between the potential benefits of CBD and the more controversial use of THC, especially when looking at treatments for mental health conditions.8

Cannabinoids and the body

Part of the brain and body is a communications system called the ‘endocannabinoid system’ that affects many important functions.9 It is made up of natural molecules produced by the body, known as endocannabinoids, and the cannabinoid receptors they interact with. Together, these parts work to regulate:

  • the central nervous system
  • appetite
  • energy metabolism
  • sleep
  • memory
  • fertility
  • cognitive function and emotions (e.g. mood and anxiety).8-13

It is thought that medical cannabis can treat various illnesses by interacting with the endocannabinoid system.

Some research suggests that if the body’s endocannabinoid system is not functioning properly it may contribute to the development of mental health conditions.5 This leads to the idea that medicines based on phytocannabinoids (plant cannabinoids) like CBD may help to regulate the endocannabinoid system and provide viable treatment options.5

How cannabidiol or CBD works

Although it is still not fully understood how CBD works, it appears to interact with a cannabinoid produced by the body called anandamide.8 Anandamide is named after the Sanskrit word ananda – meaning ‘supreme joy’.3

Research on the symptoms of psychosis have suggested that anandamide levels are linked to the severity of an individual’s symptoms.14 In a trial of CBD as a treatment for patients experiencing acute schizophrenia, findings suggested that anandamide levels increased and patients experienced improvements in their symptoms - although further research is needed.14

While it is still not completely understood if CBD is both safe and useful for treating mental health disorders there has been research on the effects of CBD for:

  • schizophrenia
  • depression
  • psychosis
  • anxiety disorders
  • bipolar disorder
  • substance-use disorders.4

Mental illness is a major public health problem

Mental illness is one of the most significant causes of ill-health and disability worldwide, and the third leading cause of disability in Australia. Roughly 4.8 million Australians experience a mental or behavioural condition,1 the most common of which are anxiety followed by mood disorders like depression.9, 11

Mental illness can also have negative impacts on an individual’s physical health. People experiencing a mental illness such as depression are at more than double the risk of death than the general population, and higher rates of physical health problems such as heart disease, asthma, hypertension, cancer and stroke.15-17

One study estimated that people with moderate to severe mental disorders like bipolar, schizophrenia and other psychotic disorders die 10-20 years earlier than the general population, on average.18

The negative impacts of mental ill-health on each individual adds up - researchers estimate that depression alone costs Australia more than $12.8 billion in healthcare costs and lost productivity per year.19

Treatment for mental disorders:

Current treatment options for mental health conditions vary depending on the type and severity of the illness and may include medication such as antidepressants and psychological treatment such as cognitive behavioural therapy.

Since existing treatments aren’t equally effective for everyone, research into alternative treatment strategies is ongoing and includes the expansion into cannabinoid medicines.

Current trials of cannabidiol to treat mental disorders

A review of multiple trials looking at the therapeutic effects of CBD concluded that while CBD is a promising treatment, larger trials are needed in order to confirm that it is an effective treatment.4

The results of these trials have described:

  • some improved symptoms for individuals who have schizophrenia
  • reduced anxiety in some people with anxiety disorders
  • some reductions in craving for people with a tobacco dependence
  • improved symptoms in people experiencing withdrawal from cannabis.4, 5

Currently, there are a lack of studies in humans assessing the effectiveness of CBD for depression and bipolar disorder.4

While these trials did not report any serious adverse side effects among their participants, there are still questions surrounding the long-term effects CBD will have on people experiencing mental illness.4

Australian research:

In Australia the Lambert Initiative for Cannabinoid Therapeutics in collaboration with the University of New South Wales is currently conducting a trial of CBD for anxiety.

More information:

If you or someone you know is experiencing symptoms of depression, consult your GP for treatment and support. For crisis support, contact Lifeline (13 11 14) or Suicide call back service (1300 659 467).

For more information about depression, try Beyond Blue, Black Dog Institute or SANE Australia.

For more information about accessing medicinal marijuana try the Therapeutic Goods Administration Special Access Scheme.

  1. Cook L. Mental health in Australia: a quick guide. Parliament of Australia; 2019.
  2. Kosiba JD, Maisto SA, Ditre JW. Patient-reported use of medical cannabis for pain, anxiety, and depression symptoms: Systematic review and meta-analysis. Social Science & Medicine. 2019;233:181-92.
  3. Mechoulam R, Parker LA. The endocannabinoid system and the brain. Annual review of psychology. 2013;64:21-47.
  4. Khoury JM, Neves MdCLd, Roque MAV, Queiroz DAdB, Correa de Freitas AA, de Fátima Â, et al. Is there a role for cannabidiol in psychiatry? The World Journal of Biological Psychiatry. 2019;20(2):101-16.
  5. Scherma M, Masia P, Deidda M, Fratta W, Tanda G, Fadda P. New perspectives on the use of Cannabis in the treatment of psychiatric disorders. Medicines. 2018;5(4):107.
  6. Kinghorn AD, Falk H, Gibbons S, Kobayashi Ji. Phytocannabinoids : unraveling the complex chemistry and pharmacology of Cannabis sativa: Springer; 2017.
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  8. Nathan DL, Elders J, Adinoff B. 21st Century Reefer Madness. Psychiatric Times. 2019;36(4):5-.
  9. Korem N, Zer-Aviv TM, Ganon-Elazar E, Abush H, Akirav I. Targeting the endocannabinoid system to treat anxiety-related disorders. Journal of basic and clinical physiology and pharmacology. 2016;27(3):193-202.
  10. Tibirica E. The multiple functions of the endocannabinoid system: a focus on the regulation of food intake. Diabetology & Metabolic Syndrome. 2010;2:5.
  11. Prospéro-García O, Amancio-Belmont O, Melendez ALB, Ruiz-Contreras AE, Méndez-Díaz M. Endocannabinoids and sleep. Neuroscience & Biobehavioral Reviews. 2016;71:671-9.
  12. du Plessis SS, Agarwal A, Syriac A. Marijuana, phytocannabinoids, the endocannabinoid system, and male fertility. 2015. p. 1575-88.
  13. Brents LK. Marijuana, the Endocannabinoid System and the Female Reproductive System. The Yale Journal Of Biology And Medicine. 2016;89(2):175-91.
  14. Leweke FM, Piomelli D, Pahlisch F, Muhl D, Gerth CW, Hoyer C, et al. Cannabidiol enhances anandamide signaling and alleviates psychotic symptoms of schizophrenia. Translational Psychiatry. 2012;2:e94.
  15. Australian Government National Mental Health Commmission. The economic cost of physical ill-health and serious mental illness. Canberra; 2016.
  16. Kang H-J, Kim S-Y, Bae K-Y, Kim S-W, Shin I-S, Yoon J-S, et al. Comorbidity of depression with physical disorders: research and clinical implications. Chonnam medical journal. 2015;51(1):8-18.
  17. Bhattacharya R, Shen C, Sambamoorthi U. Excess risk of chronic physical conditions associated with depression and anxiety. BMC Psychiatry. 2014;14(1):10.
  18. Liu NH, Daumit GL, Dua T, Aquila R, Charlson F, Cuijpers P, et al. Excess mortality in persons with severe mental disorders: a multilevel intervention framework and priorities for clinical practice, policy and research agendas. World Psychiatry. 2017;16(1):30-40.
  19. Lee YC, Chatterton ML, Magnus A, Mohebbi M, Le LK, Mihalopoulos C. Cost of high prevalence mental disorders: Findings from the 2007 Australian National Survey of Mental Health and Wellbeing. Aust N Z J Psychiatry. 2017;51(12):1198-211.

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