Medical cannabis and mental illness

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

Studies are now investigating the use of cannabidiol – a non-psychoactive cannabinoid found in the cannabis plant – to treat mental illnesses such as anxiety, depression, schizophrenia, bipolar and substance use disorders.

Therapeutic use of cannabidiol (CBD)

There’s a long history of cannabis being used 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 – the main non-psychoactive component in cannabis.⁴

Research has found CBD can produce a variety of effects, including:

• reducing the risk of epileptic fits
• preventing 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 two of the active compounds in the cannabis plant.⁶ THC is the psychoactive component that produces the ‘high’ and has 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

These two compounds have very different effects and it’s important to distinguish 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’s made up of natural molecules produced by the body, known as endocannabinoids, and the cannabinoid receptors they interact with. Together, they 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’s thought that medicinal cannabis can treat various illnesses by interacting with the endocannabinoid system.

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

How cannabidiol or CBD works

Although it’s 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 psychosis suggests anandamide levels are linked to the severity of an individual’s symptoms.¹⁴ In a trial of CBD as a treatment for people with severe schizophrenia, they found when patients had increased anandamide levels, they experienced improvements in their symptoms. Further research is needed to confirm this.¹⁴

While it’s 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

About one in five Australians will experience a mental illness and most of us will experience a mental health problem at some time in our lives.

Mental health is an essential part of overall health. Mental illnesses vary in type and severity. The most common mental illnesses are anxiety followed by mood disorders like depression.^{9, 11}

Mental illness is one of the most significant causes of ill-health and disability worldwide, and the third leading cause of disability in Australia.^{9, 11}

It can have negative impacts on a person’s physical health. People experiencing a mental illness such as depression have double the risk of early 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 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 illness add up – researchers estimate 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 illness and may include medication such as antidepressants and psychological treatment such as cognitive behavioural therapy.

Since treatments aren’t equally effective for everyone, there is ongoing research into alternative treatment strategies including 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 promising, larger trials are needed to confirm its effectiveness as a treatment.⁴

The results of these trials have described:

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

While these trials didn’t report any serious adverse side effects among their participants, there are still questions surrounding CBD’s long-term effects on mental illness.⁴

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