Americans believe marijuana is helpful in treating a variety of health problems despite a lack of available evidence. A survey published in the Annals of Internal Medicine shows that most respondents believe smoking marijuana can help with pain management and MS. Just under half believe it can relieve insomnia, anxiety and depression, ailments for which marijuana’s efficacy and safety have not been established by scientists. A study in the Lancet found marijuana does not reduce chronic pain or help replace opioids. A different study published in the journal Addiction found an association between states which have legalized medical marijuana and a reduction in prescriptions for schedule III opioids. (See also: Study finds cannabis may not be effective at treating chronic pain)