A recent study has shown that vaporizing cannabis delivers more THC to the bloodstream than smoking, according to Live Science.

In the study, which was conducted by the Substance Abuse and Mental Health Services Administration and John Hopkins School of Medicine, 17 subjects were gathered for six separate 8.5-hour sessions, separated by a week or more. All participants had not smoked or ingested cannabis in the month before the study was conducted and were tested for compliance and other impairments before the study sessions.

The participants were asked to either smoke with a pipe or vaporize using a volcano measured doses of cannabis containing a total of 0mg, 10mg or 25mg of THC over the course of the six sessions. Each time, participants were asked to fill out an impairment questionnaire as well as had their vitals measured and blood taken.

Subjects who vaporized weed had significantly higher amounts of THC in their blood compared to those who smoked an equal dose. Results from the impairment questionnaire also showed increased effects, as those who vaporized not only self-reported more side effects like dry eyes or mouth but also made twice as many mistakes on cognitive tests.

Researchers theorize that the difference is likely due to losses of THC due to combustion as well as “sidestream smoke,” or smoke that is created but not inhaled.

The study also found a disconnect between blood concentrations of THC and subjective drug effects and impairment. Researchers saw little to no correlation between blood content and continuing effects. Often, the subjective effects of cannabis intoxication as well as motor skill effects continued well after blood concentrations declined below levels that should show an effect. This is further proof that a blood test for cannabis is not a reliable measure of impairment.

Researchers concluded that the amount of THC or other cannabinoids should not be the only consideration when attempting to accurately dose cannabis. Regulators and consumers both should be aware that the method of consumption — even between seemingly similar methods like smoking and vaping whole plant cannabis — can make a big difference in how high a user becomes or how much of a given medicinal cannabinoid enters their body.