Study: Medical cannabis can reduce essential tremor

A new study has revealed that a specific synthetic cannabinoid can reduce essential tremor, without any unwanted side-effects on the brain. 

Researchers from the Department of Neuroscience at the University of Copenhagen have made a new discovery that may prove vital to future research into and treatment with medical cannabis.

Essential tremor is a neurological disorder which causes involuntary and rhythmic shaking. While the cause is unknown, it is thought to occur by the The cerebellum – which controls muscle coordination – and other parts of the brain not communicating correctly. 

Using a mouse model, the researchers have demonstrated that a specific synthetic cannabinoid (cannabinoid WIN55,212-2) reduces essential tremor by activating the support cells of the spinal cord and brain, known as astrocytes.

Previous research into medical cannabis has focused on the nerve cells, the so-called neurons.  

“We have focused on the disease essential tremor, which causes involuntary shaking, which can be extremely inhibitory and seriously reduce the patient’s quality of life,” said associate professor Jean-François Perrier from the Department of Neuroscience, who has headed the research project.

“However, the cannabinoid might also have a beneficial effect on sclerosis and spinal cord injuries, for example, which also cause involuntary shaking.”

He added: “We discovered that an injection with the cannabinoid WIN55,212-2 into the spinal cord turns on the astrocytes in the spinal cord and prompts them to release the substance adenosine, which subsequently reduces nerve activity and thus the undesired shaking.”

That astrocytes are part of the explanation for the effect of cannabis is a completely new approach to understanding the medical effect of cannabis, and may help improve the treatment of patients suffering from involuntary shaking.

Voluntary and spontaneous movements are triggered when the spinal cord’s motor neurons are activated. 

The motor neurons connect the spinal cord with the muscles and each time a motor neuron sends impulses to the muscles, it leads to contraction and thus movement. 

Involuntary shaking occurs when the motor neurons send out conflicting signals at the same time, which is why the researchers have focussed on the spinal cord.

Postdoc Eva Carlsen, who did most of the tests during her PhD and postdoc projects, commented: “One might imagine a new approach to medical cannabis for shaking, where you – during the development of cannabis-based medicinal products – target the treatment either at the spinal cord or the astrocytes – or, at best, the astrocytes of the spinal cord.

“Using this approach will avoid affecting the neurons in the brain responsible for our memory and cognitive abilities, and we would be able to offer patients suffering from involuntary shaking effective treatment without exposing them to any of the most problematic side effects of medical cannabis.”

Researchers will now carry out clinical tests on patients suffering from essential tremor to determine whether the new approach has the same effect on humans.