Despite limited evidence, Americans have an increasingly positive view of the health benefits of marijuana. Nearly two-thirds believe pot can reduce pain, while close to half say it improves symptoms of anxiety, depression, epilepsy, and multiple sclerosis, according to a new online survey of 9,003 adults.

Pennsylvania and New Jersey are among the 30 states, along with the District of Columbia, Guam, and Puerto Rico, that have legalized medical marijuana. But scientists say hard data on the health effects of pot -- both positive and negative -- are largely missing. Because marijuana is considered an illicit drug by the federal government, research has been scant, though there are efforts underway in Pennsylvania and nationally to remedy that.

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