How medical marijuana helps muscle spasms?

Marijuana's active cannabinoids do not 'block' the pain. Some research suggests there may be a secondary dopamine and endorphin reaction caused by the 'high'. What many users do find is that the peaceful, euphoric sensation puts one in a position to better endure their illness. Also, many chronic conditions affect the appetite; see cannabis as an appetite stimulant and anti nauseate.

Side note: cannabis increases the effect of narcotic pain killers.