This is only new in the US. The UK have been dispensing medical marijuana for some time.
Many patients with constant nerve pain in their legs caused by spinal and disc problems find that ingestion of small doses of marijuana relieve this pain that many other drugs can't.
However, like anything, there can be too much of a good thing. Some types of hydro grown marijuana have levels of thc that many people have trouble coping with. Look up 'cyclical vomiting syndrome caused by excessive marijuana use'. It's similar to an alcohol allergy.
