motion of muscles in the face, limbs, and trunk. The movement disorders most often discussed as candidates for marijuanabased therapies are dystonias, Huntington's disease, Parkinson's disease and Tourette's syndrome. As a general consideration, it is important to note that stress and anxiety tend to worsen the symptoms of movement disorders. Thus, marijuana's calming effect could be a primary reason why some patients claim that it brings them relief.

Dystonias are a subgroup of movement disorders that share similar symptoms: slow, sustained, involuntary muscle contractions that often cause sufferers to hold their limbs, trunks, or necks in odd positions. They may be confined to one part of the body; for example, spasmodic torticollis affects only the neck, while Meige's syndrome distorts the face. These chronic, slowly progressive disorders are often painful and can cause mild to severe disability. Some dystonias are inherited, while others occur as side effects of certain drugs. Scientists have yet to discover the specific neurological malfunctions that cause dystonias.

Several different drugs are used to treat various forms of dystonia. The most commonly prescribed drugs—benzodiazepines, baclofen, Botulinum toxin, anticholinergic agents, and tetrabenazine—merely relieve the symptoms of dystonia rather than resolving the condition itself. In many cases the relief they provide is incomplete. Baclofen (Lioresal) and benzodiazepines, including diazepam (Valium) and clonazepam (Klonopin, Rivotril), act by reducing the nervous system's ability to stimulate muscle contractions. Both drugs usually make patients drowsy and may also cause a range of additional side effects, including muscle weakness and behavioral problems. Botulinum toxin—a bacterial compound that also causes food poisoning—also blocks muscle stimulation; it produces few side effects but must be injected directly into the affected muscles. Anticholinergic drugs such as trihexyphenidyl (Artane) and diphenhydramine (Benadryl) deactivate muscle contractions; they, too, cause drowsiness and other side effects that can become severe at high doses. Tetrabenazine, although not available in the United States, is a dopaminedepleting compound available in Canada and Europe that is often prescribed for the relief certain types of dystonia.

No controlled study of marijuana in patients with dystonia