Movement disorders and neurodegenerative diseases, which are sometimes interlinked, are among the many conditions that cannabis and cannabinoids may be particularly well suited to treat.

The therapeutic use of cannabis for treating muscle problems and movement disorders has been known to western medicine for nearly two centuries. In reference to the plant's muscle relaxant and anti-convulsant properties, in 1839 Dr. William B. O'Shaughnessy wrote that doctors had "gained an anti-convulsive remedy of the greatest value."[145] In 1890 Dr. J. Russell Reynolds, physician to Queen Victoria, noted in an article in The Lancet that for "organic disease of a gross character in the nervous centers . . . India hemp (cannabis) is the most useful agent with which I am acquainted."

Muscular spasticity is a common condition, affecting millions of people in the United States. It afflicts individuals who have suffered strokes, as well as those with multiple sclerosis, cerebral palsy, paraplegia, quadriplegia, and spinal cord injuries. Conventional medical therapy offers little to address spasticity problems. Phenobarbital and diazepam (Valium) are commonly prescribed, but they rarely provide complete relief, and many patients develop a tolerance, become addicted, or complain of heavy sedation. These drugs also cause weakness, drowsiness, and other side effects that patients often find intolerable.

Extensive modern studies in both animals and humans have shown that cannabis can treat many movement disorders affecting older patients, such as tremors and spasticity, because cannabinoids have antispasticity, analgesic, antitremor, and antiataxia properties.

In the federal court brief filed in support of physicians' right to recommend cannabis, the American Public Health Association states that "marijuana is effective in treating muscle spasticity." They point out that the government's own Institutes of Medicine report on medical use of cannabis found that "current treatments for painful muscle spasms . . . have only limited effectiveness and their use is complicated by various adverse side effects."

They go on to note that "a survey of British and American MS patients reports that after ingesting marijuana a significant majority experienced substantial improvements in controlling muscle spasticity and pain. An extensive neurological study found that herbal cannabis provided relief from both muscle spasms and ataxia (loss of coordination), a multiple benefit not achieved by any currently available medications."

Cannabis also has enormous potential for protecting the brain and central nervous system from the damage that leads to various movement disorders. Researchers have also found that cannabinoids can alleviate the damage caused by strokes, as well as brain trauma, spinal cord injury, and multiple sclerosis. More than 100 research articles have been published on how cannabinoids act as neuroprotective agents to slow the progression of such neurodegenerative diseases as Huntington's, Alzheimer's and particularly Parkinson's, which affects more than 52% of people over the age of 85.

An understanding of the actions of cannabis was spurred by the discovery of an endogenous cannabinoid system in the human body. This system appears to be intricately involved in normal physiology, specifically in the control of movement.[160-164] Central cannabinoid receptors are densely located in the basal ganglia, the area of the brain that regulates body movement.

Endogenous cannabinoids (which are those cannabinoids produced by our bodies) also appear to play a role in the manipulation of other transmitter systems within the basal ganglia—increasing transmission of certain chemicals, inhibiting the release of others, and affecting how others are absorbed. Research suggests that endogenous cannabinoids play a part in the body's control of movements.

Endocannabinoids have paradoxical effects on the mammalian nervous system: sometimes they block neuronal excitability and other times they augment it. As scientists are developing a better understanding of the physiological role of the endocannabinoids, it is becoming clear that these chemicals may be involved in the pathology of several neurological diseases. Researchers are identifying an array of potential therapeutic targets within the human nervous system.

Movement disorders can be chronic disorders which arise from the loss or destruction of neurons and other structures in the brain. nterestingly, the activation of cannabinoid receptors was shown to trigger neuronal growth, suggesting that a role in neuronal regeneration.[170] Various cannabinoids found in the cannabis plant can modulate the synthesis, uptake or metabolism of the endocannabinoids that are involved in the progression of Huntington's disease, Parkinson's disease, multiple sclerosis, and Alzheimer's disease.

Parkinson's disease has been linked to dysfunction in the body's dopamine system, specifically the production of too much of the neurotransmitter glutamate and oxidative damage to dopaminergic neurons. Studies have found a tight association between cannabinoids and dopamine, and recent research has produced anatomical, biochemical and pharmacological evidence supporting a role for the endogenous cannabinoid system in the modulation of dopaminergic transmission. Furthermore, the CB1 receptor appears to be deregulated in the basal ganglia of mice with this disease. Specifically, the down regulation of the CB1 receptor may be an early event in the beginning of Parkinson's disease. A profound up regulation of the CB1 receptor may occur after Parkinson's symptoms appear.

Oxidative stress in the brain is a major hallmark of motor and neurological diseases such as Parkinson's and Alzheimer's disease. Cannabinoids are able to protect neurons from oxidative damage.[176] The neuroprotective action of cannabinoids appears to result from their ability to inhibit reactive oxygen species, glutamate, and tumour necrosis factor. THC, CBD, and synthetic AM404 all contain phenolic groups in their chemical structure and are thus able to reduce radical oxygen species. Notably CBD has extraordinary antioxidant properties and can effect Calcium homeostasis, both of which lead to positive effects against a wide range of neurodegenerative diseases.

Few clinical trials have looked at Cannabinoids and Parkinson's disease. However, research has shown that 25% of Parkinson's patients smoke cannabis and 46% of these patients report improvement resulting from side effects of long term levodopa treatment.[178] A randomized placebo controlled study using extracts of cannabis produced significant improvements in patients' cognition. The authors note that they did not see improvements in pain or sleep disorders. They speculate that the oral route (versus inhaled) of cannabis ingestion leads to too much variability of cannabinoids in blood.

Plant cannabinoids, such as CBD have been effective in experimental models of Alzheimer's, Parkinson's, and Huntington's disease. Hence, cannabinods represent an emerging therapeutic option that could be available in the near future. However, cannabinoids are still in an early phase of development but research suggest that they can be useful drugs for the treatment of many disease processes of the brain and central nervous system.