If you’re navigating the crossroads of cannabis and birth control, you’re likely thinking: How safe is this combination?

The straightforward answer isn’t so quick – join us as we explore why.

Smoking cigarettes while on birth control is dangerous. It can increase your chance of getting blood clots, as well as heart attack and stroke. These risks increase with age, especially for women over 35. The risk is also increased for women with pre-existing cardiovascular disorders.

Does smoking weed present the same risk? We asked Dr. Jordan Tishler, President of InhaleMD, a network of medical cannabis doctors in Massachusetts. But the truth is, there haven’t been any studies on the subject yet.

“However, we have also not seen a rash of case reports of clots associated with age/cannabis smoke,” says Tishler. “Overall, this is yet another good reason to avoid cannabis smoke. Use a flower vaporizer instead.”

While that’s comforting, other articles speculating on the topic have pointed out that THC elevates blood pressure. So when combined with birth control, there could be a potentially negative interaction. Simone Fischer, writer for Jezebel points out in an article that her Nuva Ring can increase blood clots by 56 percent, so in combination with blood pressure elevating THC, she’s unsure if it’s safe to mix the two. But without studies on the interaction, it’s impossible to say for sure.

Although, again, the research is lacking, it does look like it’s possible combining weed and birth control could lessen the effectiveness of birth control, especially estrogen-based contraceptives.

Tishler points out that “THC seems to interact with oral estrogen by increasing their level.” Although, he continues, that’s “not likely to undermine the effectiveness of OCP [oral contraceptive pills].”

Does CBD affect birth control pill effectiveness like THC may?

There isn’t enough research on CBD and birth control either to say anything conclusively, but it does look like CBD could potentially make estrogen-based contraceptives, like the pill, as well as patches, injections, and rings less effective. In fact, CBD’s potential to interact with birth control is stronger than THC’s.

“CBD decreases the level [of oral estrogen], which would likely make OCP less effective,” says Tishler.

This is because of how CBD is digested in the liver. A 2011 study found that cannabidiol can inhibit certain enzymes, and these are the same enzymes which metabolize estrogen birth control pills. You can read more about these enzymes and possible CBD drug interactions in our full explainer.

Because of CBD’s ability to inhibit the enzymes that break down estrogen birth control, it can also increase breakthrough bleeding. Shawn Zylenko, RN and certified cannabis nurse, explains in an article for the Natural Health Services of Canada that mixing other things with birth control and CBD could increase the potential for interaction even more. “Cigarette smoking, chronic alcohol use, and St. John’s Wort are three big players and should be avoided while on birth control, and especially when using CBD,” Zylenko writes.

However, all birth control methods aren’t created equally. Tishler tells Herb that while estrogen-based forms of birth control may be compromised by cannabis consumption, progesterone-only contraceptives are more likely to be fine. “CBD will increase progesterone levels, which likely do not undermine progesterone only BC,” Tishler explains. Although, he also recommends, regardless of the kind of birth control you’re on, using condoms and considering an IUD when taking CBD.

As I’m sure you’ve guessed, there aren’t studies on the effects of combining cannabis edibles and birth control.

However, Tishler says the “the manner of ingestion is not relevant.” If you’re eating a high CBD edible, then there’s a chance it could interfere with your estrogen birth control’s effectiveness.

As for high THC edibles, the jury’s still out. If you’re worried about increased blood pressure, it’s probably not the best combination. But if you’re more concerned about your pill’s effectiveness, it looks like THC is less detrimental than CBD.

Again, there are no studies on vaping and birth control. The risk is also going to depend on whether you’re vaping THC or CBD. Vaping high CBD strains could potentially interfere with birth control’s effectiveness. However, due to the low dose of most CBD vape pens, you’re likely not ingesting enough CBD to inhibit the metabolism of estrogen. That being said, until we have more research on the topic, it’s impossible to say for sure.