Parkinson's disease is the second most common neurological illness in the United States, causing tremors, slowness of movement, postural instability, and impaired balance and coordination. But findings from a new review suggest symptoms of the condition could be improved with marijuana.
The review was led by Prof. Zvi Loewy, from the Touro College of Pharmacy in New York, NY. It is published in the journal Parkinson's Disease.
Recently, another study suggested that tetrahydrocannabinol (THC) - the active compound in marijuana - reduced beta-amyloid levels in nerve cells, a protein considered a hallmark of Alzheimer's disease.
In the U.S., Parkinson's disease (PD) affects about 1 million people. It is progressive, which means it gets worse over time, and it occurs when a person's brain stops producing dopamine.
Dopamine is a neurotransmitter that plays a key role in movement as well as in cognitive and psychological functions.
There is currently no cure for the disease; treatments carry with them several limitations and do not slow progression of PD.
'Marijuana should be studied for PD pain relief'
The researchers from this latest study say recent research has indicated that the endocannabinoid system plays an important role in PD. In detail, components of this system "are highly expressed in the neural circuit of basal ganglia, which is part of a complex neuronal system," they say.
- PD usually affects people over the age of 60
- The four primary symptoms are tremor, rigidity, slowness of movement, and postural instability
- There is currently no cure for the condition.
The neuronal system they mention organizes activities from certain cortical regions that are active in movement control.
"When we started doing this review," says Prof. Loewy, "the therapies out there were basically for motor symptoms, but Parkinson's also has non-motor symptoms that greatly impact the quality of a person's life."
To dig deeper, he and his team conducted a thorough literature review on studies of marijuana.
The most compelling finding was that chemical components of marijuana yield benefits in the wake of different PD symptoms.
For example, Prof. Loewy notes that marijuana has been found to relieve pain in other diseases, adding that it should be studied for pain relief in people with PD. Pain affects nearly 50 percent of people with the condition, the researchers note.
But why is marijuana specifically promising for PD? According to the team, the cannabinoid compounds in marijuana bind to dopamine receptors to reduce the effects of reduced dopamine in the brain.
"Essentially, the compounds replace the normal compounds that are adversely affected by Parkinson's," Prof. Loewy says.
Preventing neuron damage could slow disease progression
But the big finding from their review centers around the anti-inflammatory and antioxidant effects of marijuana, which may prevent neuron damage.
The researchers say inflammation can damage neurons that produce dopamine - the lack of which contributes to movement problems in Parkinson's. As such, they say preventing neuron damage could slow PD progression.
They note that there is a need for safer drugs to treat PD, adding that cannabis "may provide a viable alternative or addition to the current treatment of Parkinson's disease."
However, as with any substance, there are risks to take into account. Recent research has uncovered some downsides to marijuana use, including memory loss, increased osteoporosis risk, and impaired blood vessel function.
Furthermore, a study published in April of this year suggested marijuana use may reduce dopamine in the brain, so how this could affect PD should be taken into account.
The researchers from this latest study conclude that "further studies are needed to provide more data on efficacy, safety, pharmacokinetics, and interactions of cannabinoids."