Researchers kept the levels low for two reasons, Ware explained. One was to minimize the psychoactive effects, such as feeling lightheaded, dizzy, detached, nauseous or euphoric. Secondly, because this was a randomized, controlled clinical trial, minimizing the obvious signs of being "high" helped keep participants in the dark about what potency they were smoking.
In an accompanying commentary, Dr. Henry McQuay, a professor in the chronic pain unit at Oxford University in England, called the study well-designed, adding that it provides more evidence cannabis can help relieve pain.
But the unwanted side effects of cannabis can be significant, McQuay said.
"If you regard each paper like a brick in a wall, we have a number of studies, including this one, that suggest some pain patients are helped by cannabis," McQuay said. "The usual caveat is, 'Do the side effects to the nervous system outweigh the benefits, if they have to push the dose?'"
In his experience working with pain patients, few have seen long-term benefits of smoked cannabis, he said. Most find morphine and other painkillers more effective.
Side effects are a real problem with using smoked cannabis, Ware said. While recreational users are seeking an altered state of mind, research shows that legitimate medical marijuana users are not looking to get high. Instead, they only want to smoke what they need to reduce their pain so they can work and function more normally.
Efforts to legalize marijuana for medical purposes has been controversial in the United States. While federal law prohibits marijuana use, in 1996, California became the first state to legalize medical marijuana usage with a prescription from a doctor. More than a dozen states have followed suit.
Yet under the Bu
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