A series of trials published by the University of California Center for Medicinal Cannabis Research in May showed cannabis can help patients suffering from neuropathic pain, commonly caused by degenerative diseases like multiple sclerosis or fibromyalgia. Neuropathic pain is also a common side effect of chemotherapy and radiation.
Study participants on cannabis reported a 34 to 40% decrease in pain compared to the 17 to 20% decrease seen from patients on a placebo drug.
A 2011 study published in the journal Addiction found marijuana has little long-term effect on learning and memory, according to TIME.com. The study authors followed nearly 2,000 Australian adults, aged 20 to 24, for eight years. They concluded that the adverse impacts of cannabis use (shown in earlier studies) were either related to pre-existing factors or were reversible after even extended periods of use.
The good news is that marijuana has a low rate of addiction; estimates place it at about 9% of users. And as NORML points out, "the consumption of marijuana — regardless of quantity or potency — cannot induce a fatal overdose."