BOSTON (CBS) — A long-awaited study on the health effects of marijuana found both therapeutic effects and health risks associated with the substance.

The National Academy of Sciences’ review of a number of studies published since 1999 found that patients treated with cannabis for chronic pain were likely to have a reduction in symptoms. For adults with multiple sclerosis-related muscle spasms, cannabis taken orally was found to improve symptoms.

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At the same time, the study found in states where marijuana use is legal, there is an increased risk of overdose among children. The academy also says there is evidence of an increased risk of mental illnesses like schizophrenia and anxiety disorders for marijuana users. Heavy marijuana users are more likely that non-users to have suicidal thoughts, according to the results.

Researchers found more than 22 million Americans, ages 12 and over, have used marijuana in the past 30 days. Of those users, 10 percent were for medical purposes only and just over a third for a combination of medical and recreational purposes. In the study, researchers found “moderate” evidence on marijuana dependency, and concluded smoking marijuana during pregnancy is linked to low birth weight babies.

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In the report, the Academy wrote, “as laws and policies change, research must also.”

WBZ NewsRadio 1030’s Lana Jones reports

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