Cannabis and Parkinson’s disease: everything we know so far

Parkinson’s disease is the fastest growing neurological condition in the world, but cannabis has been shown to ease a range of symptoms from stiffness and tremors to anxiety, poor sleep and impaired cognitive function. Here’s what the science says.

Parkinson’s disease (PD) is a neurodegenerative disorder that affects more than 10 million people globally. According to Parkinson’s UK, PD is the fastest growing neurological condition in the world, with roughly one in every 37 people likely to be diagnosed with the condition in their lifetime.

While research is still scarce, several studies and patient surveys indicate that cannabis, particularly the cannabinoids THC and CBD, shows significant promise as a therapy for a number of symptoms of PD and could potentially slow its progression. 

This World Parkinson’s Day (Tuesday 11 April), we’re exploring the science behind cannabis and PD as well as highlighting how, and why, patients are using it to find relief. 

What is Parkinson’s disease? 

Parkinson’s causes parts of the brain to deteriorate over time and is primarily caused by a loss of nerve cells in the substantia nigra, an area of the brain that is critical to producing dopamine. As dopamine is a neurotransmitter that facilitates movement and regulates mood, people with PD will often experience physical and psychological symptoms including tremors, muscle spasms, stiffness, pain, anxiety, depression, poor sleep, confusion and more. 

There is no exact known cause of PD, but experts believe a combination of genetic and environmental factors play a role. PD generally doesn’t present in people before the age of 50—with symptoms worsening with age—and while there is no known cure, physio and occupational therapy, medication, and in some cases, surgery, can help patients manage Parkinson’s. One common medication called Levodopa, however, is known to sometimes cause dyskinesia, an involuntary erratic movement of one’s body and/or limbs. 

Cannabis, the endocannabinoid system and the substantia nigra 

Cannabis could play a promising role in alleviating symptoms of PD while providing patients with a better quality of life.

It’s well known that the hundreds of compounds and cannabinoids—including THC and CBD—found in cannabis interact with, and complement, the body’s endocannabinoid system (ECS). The ECS is responsible for maintaining various physiological functions as well as overall health and involves at least two types of cannabinoid receptors—one set that’s mainly located in the central nervous system (CB1) and the other in the organs and cells of the immune system (CB2).

An area of the body that contains some of the highest concentrations of CB1 receptors is the substantia nigra, the same part of the brain that’s impacted by PD. One keystone 2016 meta-analysis suggests that the activation of CB1 receptors neuro-protects against the damage of dopamine-regulating cells as well as levodopa-induced dyskinesia. The same study found that cannabis shows great promise in treating both motor and non-motor PD symptoms and could delay, or even stop, progressive degeneration of the brain’s dopamine-producing system.

How cannabis can help with symptoms of Parkinson’s

While the research is still relatively limited and draws on small sample sizes, a number of studies have shown that cannabis can help improve and/or alleviate both physical and psychological symptoms related to Parkinson’s. 

A 2014 study published in the Journal of Psychopharmacology found that amongst the 22 PD patients observed, cannabis significantly reduced tremors, rigidity, and bradykinesia (slowness of movement), and improved pain and sleep with very minimal adverse side effects. 

One meta-analysis looking specifically at CBD and Parkinson’s, published in the Journal of Clinical Psychopharmacology in 2019, found that CBD oil improved quality of life in Parkinson’s patients by reducing symptoms of psychosis, depression, anxiety and sleep disorders. 

More recently, a survey of Parkinson’s patients in Germany, where medical cannabis has been prescribed to treat PD symptoms since 2017,  found that more than half of patients with PD who consume cannabis have found it to be beneficial. Over 40% of users reported that it helped manage pain and muscle cramps, and more than 20% of users reported a reduction of stiffness, freezing, tremor, depression, anxiety, and restless legs. 

Another patient survey from the Parkinson’s Foundation (see graph above) found that one-quarter of US-based Parkinson’s patients had consumed cannabis within the previous six months and less than 13% of consumers reported negative side-effects. The main symptoms PD patients used cannabis for included anxiety, sleep disorders, pain, stiffness and tremors. A second US patient survey, this time conducted by researchers at the University of Colorado, found that 70% of PD patients used cannabis to manage symptoms, with reported improvements in pain, anxiety, agitation and sleep.

What’s next for Parkinson’s and cannabis in the UK?

Despite medical cannabis being legal in the UK since 2018, the NHS will not prescribe cannabis-based medicines for Parkinson’s claiming there is not enough robust scientific evidence to show its efficacy. Parkinson’s UK, however, recognises that there could be scientifically significant benefits when it comes to cannabis and PD symptoms and is undergoing a world-first clinical trial with Kings College London testing whether CBD can treat psychosis related to Parkinson’s.

Even TV presenter Jeremy Paxman, who recently explored the potential of CBD in managing Parkinson’s symptoms in a 2022 ITV documentary, has admitted he would be open to trying cannabis-based medicines for his own PD symptoms.

Parkinson’s UK conducted a 2019 survey of UK-based PD patients to assess attitudes towards using cannabis for symptom relief. The survey found that 59% hadn’t used cannabis-derived products before, but would consider using them to control their symptoms, and that “overwhelmingly, people with Parkinson’s would continue to use, or start using, cannabis-derived products if robust evidence became available that they’re safe and effective in treating Parkinson’s symptoms.”

DISCLAIMER: This article is intended for educational purposes only. Always speak to your doctor before making any changes to your medical care. 

• Study suggests Gb Sciences’ cannabinoid mixtures could treat Parkinson’s
• What are the benefits of CBD for Parkinson’s disease?
• Parkinson’s disease and CBD: New studies may reveal positive effects
• Study: cannabis ‘effective’ in older patients with chronic conditions
• Quarter of Parkinson’s patients have consumed cannabis