Parkinson’s is a common neurodegenerative disorder that affects the brain and nervous system. The condition is characterised by unintended or uncontrollable movements, such as tremors, stiffness and bradykinesia (slowness of movements), as well as difficulties with balance and coordination. Non-motor symptoms of Parkinson’s include psychosis, cognitive impairment, anxiety, and depression; however, there are more than 40 known symptoms of Parkinson’s, and everyone is affected differently.
The most prominent signs and symptoms of Parkinson’s occur when nerves in the basal ganglia, the area of the brain that controls movement, become damaged and/or die. These nerve cells produce dopamine, a type of neurotransmitter that plays a number of essential roles in the body. When nerve cells become impaired or die, they produce less of this important chemical. It’s not completely understood what causes the nerve cells to die.
It is estimated that around 1 in 37 people alive in the UK today will be diagnosed with Parkinson’s in their lifetime. The condition is more common in older people with current figures showing that prevalence rates almost double every five-year interval between the ages of 50 and 69.
Treating Parkinson’s disease
There is no cure for Parkinson’s, and current therapies focus on symptom relief. This includes medicines that help to increase the level of dopamine and other chemicals in the brain, and control non-movement symptoms. The main therapy for Parkinson’s is levodopa, which can help nerve cells replenish the brain’s supply of dopamine. However, this therapy only addresses the motor symptoms of Parkinson’s and is associated with several side effects, including nausea and vomiting, low blood pressure, dyskinesia (uncontrolled, involuntary movement), and restlessness.
Parkinson’s and medical cannabis
As attitudes towards cannabis have continued to evolve in recent years, there has been renewed interest in the therapeutic potential of the plant and its derivatives across a wide range of clinical settings. A large number of countries, including the UK, have now legalised the medicinal use of cannabis for the treatment of various conditions, and studies continue to show increased patient interest in these therapies.
According to a 2017 investigation, around 44% of the US population with Parkinson’s and multiple sclerosis (MS) currently uses cannabis. The respondents reported high efficacy of cannabis with 59% reporting that they had reduced prescription medication since beginning cannabis use. Cannabis users also reported lower levels of disability when compared to non-users.
But is there any evidence to support the use of cannabis and cannabis-based medicines in this setting?
Cannabis contains hundreds of active compounds, many of which are known to hold significant therapeutic properties. The most common among these compounds are cannabinoids. Cannabinoid receptors are expressed throughout our bodies, particularly in the central nervous system (CB1) and the immune system (CB2). There is also a significant presence of cannabinoid receptors in the basal ganglia – the area of the brain affected by Parkinson’s disease. These receptors make up part of the endocannabinoid system, which is involved in a number of physiological functions, including the modulation of mood, cognition, motor, and pain.
Studies of medical cannabis for Parkinson’s in animals
In a study of mice, loss of CB1 receptors resulted in decreased locomotor skills – a finding that supports the importance of cannabinoids in the control of movement by the basal ganglia. Another study of Parkinson’s in marmosets demonstrated that treatment with Nabilone, a synthetic cannabinoid agonist, decreased total dyskinesia when co-administered with levodopa and increased the duration of efficacy of levodopa. Further studies indicate that activation of CB1 receptors neuro-protects against dopaminergic lesions and levodopa-induced dyskinesia.
Human studies of Parkinson’s
An observational study, published in 2014, evaluated the effects of smoking cannabis in 22 patients with Parkinson’s disease. The researchers measured responses to cannabis at baseline and 30 minutes after consumption using the Unified Parkinson Disease Rating Scale, visual analogue scale, present pain intensity scale, and the Short-Form McGill Pain Questionnaire. They found that motor symptoms, including tremors, rigidity, and bradykinesia, improved significantly after cannabis consumption. Cannabis treatment was also associated with improvements in non-motor symptoms with patients demonstrating improved sleep and pain scores. The researchers concluded that “cannabis might have a place in the therapeutic armamentarium of [Parkinson’s disease]”; however, they noted that more extensive, controlled studies were needed to verify these results.
In 2022, a group of Australian researchers aimed to assess the effects of cannabis in Parkinson’s disease in a systematic review. They compiled the best available evidence to help guide patients and their families, clinicians and researchers to make informed decisions regarding this potential treatment. While they reported a lack of evidence significant enough to recommend the use of cannabis, the researchers noted that current clinical evidence does suggest a potential benefit for several Parkinson’s motor and non-motor symptoms, including tremors, anxiety, pain, sleep quality, and quality of life. Again, they recommended further investigation into the potential of medical cannabis in this setting.
While medical cannabis is not currently recommended by the National Institute of Health and Care Excellence (NICE) for the treatment of Parkinson’s, it may be possible to get a prescription from a private cannabis clinic in cases where other options have proven ineffective. To learn more about getting a medical cannabis prescription in the UK, take a look at our leafie guide.