Severe pain is most often treated with opiates. These are addictive, and tolerance develops, resulting in the need for increased dosage. The risk of severe side effects is great. Synthetic analgesics are non-addictive but they are often not powerful enough.
Cannabis has fewer side effects than other analgesics. One strange fact is that more experienced users get a greater pain relieving effect from cannabis than novices. Experienced users also are able to function normally and ignore the psychoactive effects.
Dr. J. Russell Reynolds, Fellow of the Royal Society and Physician to Queen Victoria reported in the Lancet in 1890 that he had been prescribing cannabis for 30 years and considered it "one of the most valuable medicines we possess". According to Reynolds Indian hemp remained effective as an analgesic for months and even years without an increase in the dose.
