It is not clear whether medical cannabis is a useful treatment for any condition. Evidence is moderate that it helps in chronic pain and muscle spasms. Low quality evidence suggests its use for reducing nausea during chemotherapy, improving appetite in HIV/AIDS, improving sleep, and improving tics in Tourette syndrome. When usual treatments are ineffective, cannabinoids have also been recommended for anorexia, arthritis, glaucoma, and migraine. It is unclear whether American states might be able to mitigate the adverse effects of the opioid epidemic by prescribing medical cannabis as an alternative pain management drug.
It is recommended that cannabis use be stopped in pregnancy.
Nausea and vomiting
Medical cannabis is somewhat effective in chemotherapy-induced nausea and vomiting (CINV) and may be a reasonable option in those who do not improve following preferential treatment. Comparative studies have found cannabinoids to be more effective than some conventional antiemetics such as prochlorperazine, promethazine, and metoclopramide in controlling CINV, but these are used less frequently because of side effects including dizziness, dysphoria, and hallucinations. Long-term cannabis use may cause nausea and vomiting, a condition known as cannabinoid hyperemesis syndrome (CHS).
A 2016 Cochrane review said that cannabinoids were “probably effective” in treating chemotherapy-induced nausea in children, but with a high side-effect profile (mainly drowsiness, dizziness, altered moods, and increased appetite). Less common side effects were “ocular problems, orthostatic hypotension, muscle twitching, pruritus, vagueness, hallucinations, lightheadedness and dry mouth”.
Evidence is lacking for both efficacy and safety of cannabis and cannabinoids in treating patients with HIV/AIDS or for anorexia associated with AIDS. As of 2013, current studies suffer from the effects of bias, small sample size, and lack of long-term data.
A 2017 review found only limited evidence for the effectiveness of cannabis in relieving chronic pain in several conditions. Another review found tentative evidence for use of cannabis in treating peripheral neuropathy, but little evidence of benefit for other types of long term pain.
When cannabis is inhaled to relieve pain, blood levels of cannabinoids rise faster than when oral products are used, peaking within three minutes and attaining an analgesic effect in seven minutes. A 2014 review found limited and weak evidence that smoked cannabis was effective for chronic non-cancer pain. A 2015 meta-analysis found that inhaled medical cannabis was effective in reducing neuropathic pain in the short term for one in five to six patients. Another 2015 review found limited evidence that medical cannabis was effective for neuropathic pain when combined with traditional analgesics.
A 2011 review considered cannabis to be generally safe, and it appears safer than opioids in palliative care.