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NIDA. (2017, March 6). Two More Things We’ve Learned About Secondhand Marijuana Smoke. Retrieved from

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The NIDA Blog Team
March 6 2017
A cloud of smoke

When we wrote about secondhand marijuana smoke in 2014, we still had many unanswered questions about its effects. Here’s what research since then has found:

  1. It’s hard to get “high” off of secondhand marijuana smoke. How much a room is ventilated could make the difference. A study found that if you’re in an unventilated room (the windows and doors are closed), and smoke is blown directly in your face for a while, it might make you feel a little sleepy and your thinking “fuzzy.” If the room is ventilated, this reaction probably won’t happen. But even if you feel normal, the smoke could get into your body and you could still fail a drug test.
  2. A study in rats indicates that secondhand marijuana smoke might harm your heart and blood vessels. In fact, when the rats inhaled the smoke for just one minute, their hearts and blood vessels didn’t function as well as normal for the next hour and a half! A study like this hasn’t been done in humans, but it’s troubling.

Researchers still have many unanswered questions, but the available evidence suggests that while inhaling secondhand marijuana smoke isn’t as bad for your health as smoking marijuana, it isn’t harmless, either.

“Spice is like marijuana”—true or false? Find out here.