We’ve all heard that sprinkling a little tobacco in your joint amplifies your high. A new study out of University College London has determined that’s a myth.

A team of researchers enlisted 24 experienced cannabis consumers to take part in four separate experiments: smoking joints with cannabis and tobacco, cannabis and a placebo, tobacco and a placebo, and a placebo of both. The researchers then tested their memories and measured their heart rates and blood pressure, while the participants reported how high they felt.

Participants felt no difference in their level of inebriation after smoking cannabis with tobacco versus cannabis by itself, researchers found.

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Interestingly, those who smoked cannabis by itself experienced the most memory impairment. The researchers said adding tobacco appeared to reduce memory issues, possibly because the nicotine concentration in tobacco can actually improve concentration.

There were some negative repercussions to the combination, however. Participants’ heart rates climbed the most when consuming cannabis with tobacco. They also experienced a slight increase in blood pressure.

This demonstrates that combining cannabis and tobacco lead to greater heart risks than smoking cannabis by itself, say the researchers.

In other words: keep it clean, folks.

h/t Men’s Health