There is considerable evidence for cannabis being effective to treat a variety of conditions.
Certainly quite good evidence exists showing it is effective in helping patients with spasticity.
Indeed a cannabis product – Sativex – is prescribed legally to patients with multiple sclerosis if their spasticity has become resistant to other drugs.
It has also been shown to reduce the number of times they need to empty their bladder.
However, cannabis has also shown to be useful in chronic pain, particularly non-cancer pain and neuropathic pain, which is caused by damage to the brain or nervous system.
There are a whole variety of other conditions in which evidence shows it can be useful, for example managing the nausea that comes with chemotherapy and improving sleep.
It can be used as an appetite stimulant for patients in debilitating conditions, such as those with HIV.