No one fully understands how the myriad blend of chemicals in the cannabis plant acts within the brain. One way to advance our knowledge is to examine what happens when our brain’s endogenous cannabis neurotransmitter system dysfunctions. One particular condition of interest is Restless Leg Syndrome.
Restless Leg Syndrome generally worsens with age and often disrupts sleep. The main symptom, as the name suggests, is a nearly irresistible urge to move the legs. Getting up and moving around helps the feeling temporarily go away; however, there is no cure and the symptoms can last a lifetime. The effectiveness of one novel therapy provides insight into a potential link between the endogenous cannabis neurotransmitter system and the neurotransmitter dopamine.
What is the role of dopamine in the brain? The function of each neurotransmitter depends entirely on the function of the structure in which it is located. Deep within your brain is a region called the basal ganglia. The neurons in the basal ganglia are responsible for producing normal well-controlled smooth movements. The level of the neurotransmitter dopamine in these nuclei is much higher than in most surrounding brain regions. Therefore, scientists have concluded that dopamine within the basal ganglia is critically involved in the control of movement. Furthermore, if we expose our brain to a drug that impairs the function of dopamine, then our ability to move is greatly impaired. Dopamine is obviously critical for movement and it is easy to see how dopamine dysfunction might be involved in Restless Leg Syndrome.
Dopamine is also found in the retina of your eye and in your hypothalamus, structures that have nothing to do with movement. Dopamine also is released into small regions deep within the frontal lobes; when this happens, you experience a feeling of pleasure. Dopamine is not the brain’s only “feel good” neurotransmitter. For example, the release of acetylcholine in the septal area produces a feeling a well-being and joy, while the release of the neurotransmitters enkephalin or anandamide within the brain produces a feeling of euphoria. Surprisingly, dopamine plays virtually no role in the euphoria produced by cannabis. In fact, cannabis reduces (!) the release of dopamine, which is why levels of dopamine increase when using cannabis. Essentially, the levels of dopamine increase in the brain after cannabis use because the neurons have stopped releasing it.
So, what explains the benefits of cannabis for Restless Leg Syndrome? The brains of patients with Restless Leg Syndrome may be in what is called a “hyper-dopaminergic state” – too much dopamine is being released inside the basal ganglia.
Recent studies have shown that chronic cannabis use is associated with reduced dopamine synthesis capacity. Thus, the efficacy of cannabis in patients with Restless Leg Syndrome may be due to its ability to prevent the excessive release of dopamine and restore normal neural activity in the basal ganglia.
It is too soon to claim that we understand the role of the brain’s endogenous cannabis system in Restless Leg Syndrome. However, as more information accumulates it might one day be possible to design effective cannabis-like drugs for a variety of human disorders of the brain.
Ghorayeb I (2020) More evidence of cannabis efficacy in restless legs syndrome. Sleep and Breathing (2020) 24:277–279. https://doi.org/10.1007/s11325-019-01978-1
Bloomfield MA et al (2014) Dopaminergic function in cannabis users and its relationship to cannabis-induced psychotic symptoms. Biol Psychiatry 75(6):470–478. https://doi.org/10.1016/j.biopsych.2013. 05.027.