Cannabidiol as a way to reduce anxiety in patients with Parkinson's disease?

Potential uses of cannabidiol

Cannabidiol (CBD) is one of the many cannabinoid compounds found in cannabis sativa. Although CBD and tetrahydrocannabinol (THC) have a similar molecular structure, CBD does not directly stimulate cannabinoid receptors CB₁ and CB₂, unlike THC, and therefore does not have its psychoactive effects.

CBD has a wide range of beneficial effects – antipsychotic, anti-inflammatory, neuroprotective, and anxiolytic. However, there has been little known about its use and effects on anxiety in patients with Parkinson's disease. The aim of the study published in February this year was to evaluate the effect of acutely administered 300 mg CBD on anxiety and tremors induced by situational anxiety (SPST - simulated public speaking test) in these patients.

Anxiety as a significant comorbidity in Parkinson's disease

Parkinson's disease affects 3.3% of the population over the age of 64. It is the most common disorder of the basal ganglia, the brain structure responsible for controlling motor functions. The primary pathology of the central nervous system in Parkinson's disease is the degeneration of dopaminergic cells in the pars compacta substantia nigra with subsequent dopamine deficiency in the striatum. Degenerative involvement of cells also affects the nucleus basalis, locus coeruleus and nucleus dorsalis raphae with secondary disruption of the cholinergic, adrenergic, and serotonergic systems.

This dysfunction is reflected in other typical symptoms of Parkinson's disease. These include postural, vegetative, and psychological disorders – depression, anxiety, apathy, sleep disturbances, psychoses, etc. Anxiety appears in up to 67% of patients with Parkinson's disease and further accentuates motor symptoms, especially tremor.

Methodology and conduct of the study

The randomized double-blind placebo-controlled study included a total of 24 patients (22 males, average age 64 years) with Parkinson's disease. The average duration of the disease in participants was 6.5 years. Most patients were on levodopa therapy (19 people). Other antiparkinsonian drugs used by participants were pramipexole (11 patients), amantadine (8), selegiline (3), biperiden (2), and entacapone (1). Other medications included simvastatin (4 times), omeprazole (3 times), atenolol (2 times), losartan (2 times), propranolol, nifedipine, amiodarone, melatonin, fenofibrate, levothyroxine, acetylsalicylic acid, and finasteride (1 patient each).

After taking placebo/300 mg CBD, participants underwent the SPST (each twice in a 15-day interval). During the test, their heart rate, blood pressure, tremor frequency, and amplitude (measured by accelerometer) were monitored. Visual Analog Mood Scales (VAMS) and self-assessment by participants were also used for analysis.

Results

Regarding anxiety assessed using VAMS, significant differences were found between the CBD group (anxiety factor [1; 21] = 6.27; p = 0.021) and the placebo group (anxiety factor [2.75; 57.66] = 5.26; p < 0.001). Cognitive impairment and discomfort, also assessed using VAMS, did not significantly differ between the CBD/placebo groups. In patients who took CBD, there was also a significant effect on tremor amplitude measured by the accelerometer compared to those on placebo.

Discussion and conclusion

This is currently the only study of its kind to demonstrate the effect of CBD on induced anxiety and tremor in patients with Parkinson's disease. These findings are consistent with experiments confirming the anxiolytic effects of CBD. In the future, CBD could be an alternative treatment for anxiety in patients with Parkinson's disease. However, further and larger studies are needed.

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Source: de Faria S. M., de Morais Fabrício D., Tumas V. et al. Effects of acute cannabidiol administration on anxiety and tremors induced by a simulated public speaking test in patients with Parkinson's disease. J Psychopharmacol 2020; 34 (2): 189–196, doi: 10.1177/0269881119895536.