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En español | Evaluating medical marijuana research disease by disease is not easy, hampered as it is by the federal government’s ban on government-supported data collection. Observational studies — in which users simply report their experiences — may look rosy. Animal and test-tube studies also can sound promising. But plenty of stuff that helps mice or a clump of cells in a petri dish may not help us humans. Despite these obstacles, there are some conditions and diseases for which cannabis is clearly a useful treatment. Others, not so much.



Chronic pain



More than 600,000 Americans turn to cannabis for relief from chronic pain — and the scientific evidence for its effectiveness is substantial. In gold-standard randomized clinical trials of people who had agonizing health concerns — peripheral neuropathy (nerve pain from diabetes), spinal cord injury, HIV or complex regional pain syndrome, cancer, chemotherapy, muscle and joint problems, rheumatoid arthritis and multiple sclerosis — cannabis reduced pain by 40 percent, according to the 2017 NASEM report.

In a recent Canadian study, cannabis even soothed arthritic lab rats. Surprisingly, there’s little evidence (yet) from human studies for the most common form of arthritis, osteoarthritis — the wear-and-tear joint disease affecting 50 percent of adults age 65-plus. Clinical trials are underway. But who’s waiting? Arthritis was the top reason older adults used cannabis in a 2019 Colorado survey, followed by back pain. Overall, 79 percent said it helped.

BOTTOM LINE: It seems to help