Dear Dr. Roach: My neurologist recently suggested that I use marijuana for insomnia and chronic pain. 
Medical cannabis is legal where I live. Edibles work well but it’s hours before they take effect. Smoking and vaping both provide immediate relief. Could you say anything about the relative health risks of smoking vs. vaping cannabis products?
— M.A.
Answer: I can’t recommend either vaping or smoking cannabis, as both have health risks. I understand you are looking for which one causes less harm, but there is less known about vaping. What is clear is that some illegal vaping products for cannabis contain vitamin E acetate, which appears to be one major cause of e-cigarette or vaping-associated lung injury (EVALI).
Legal vaping products, if you live in a state that allows them, should not contain this additive, although there are recent reports of EVALI in people who have purchased vaping products at legal dispensaries in Massachusetts.
In contrast, the dangers of smoking are well known, although the amount of cannabis smoked is very low compared with tobacco.
Both smoking and vaping cannabis have risks, but I suspect there remain higher risks with vaping than with smoking.
