People have mixed experiences when it comes to weed and sex—and a new study could explain why.

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It turns out that cannabis has a "bidirectional" effect on sexual functioning, according to research published in the journal Current Sexual Health Reports last week. That means it literally has opposing effects, in this case depending on how much and how often you consume.

"Low and acute doses of cannabis may enhance sexual human sexual functioning" such as sexual desire and satisfaction, the study found. That said, "chronic use of higher doses of cannabis may lead to negative effects on sexual functioning such as lack of interest, erectile dysfunction, and inhibited orgasm."

That could explain the disparate responses to a 2003 survey, which asked 104 participants about their experience with marijuana and sex.

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About 25 percent said marijuana "always" or "often" increased their libido, 40 percent said it "sometimes" helped, and about 35 percent said it rarely or "never" did. Asked whether they considered marijuana a sexual enhancer, the participants were split 50/50, Psychology Today reported.

Dr. Richard Balon, the lead author of the study released last week, said that more research is needed to confirm what biological mechanisms are involved to understand why cannabis has these conflicting effects. But he theorized that it could have to do with marijuana's impact on the endocrine system, which is responsible for regulating hormones such as testosterone.

Just how much marijuana is too much, though?

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Because people build tolerances to cannabis over time, the answer is going to be different for everyone. Dr. Perry Solomon, a researcher at the medical marijuana site HelloMD, told The Fresh Toast that those looking to combine weed and love-making should avoid strains high in THC that are known for their sedating properties.

Solomon recommends that men stick to strains that contain between 10 and 14 percent THC, the main psychoactive ingredient in cannabis, to ensure that you're able to maintain an erection.

To sum up, marijuana has historically been used as an aphrodisiac that can enhance the pleasure of sex. But getting too stoned could be counterproductive in bed.