This is how long cannabis stays in your system

It's a classic. You've got medical tests coming up, and to keep a straight face, you have no choice but to test negative for cannabis. So you say good-bye to joints for a week or 10 days, just to clear your system of all traces. But this recent discovery may well call into question everything you thought you knew.

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300 years old

When it comes to detecting cannabis, not all tests are created equal. So suggests a study published in the Journal of Archaeological Science. After exhuming and analyzing human remains dating from the 17th century in the crypt of Ca' Granda, the former major hospital in Milan, Italy, archaeologists came to this conclusion. They were surprised to find traces of the psychotropic plant.

It was in the bones, mainly femurs, that the discovery was made.

The results obtained on bone samples revealed the presence of two molecules: 'THC (tetrahydrocannabinol) and CBD (cannabidiol), highlighting the administration of cannabis', explained Gaia Giordano of the University of Milan, who took part in the study.

This is the first time in history that we have detected cannabis on human remains in an archaeological context.

Medical use?

How did these molecules get there? For the experts, the explanation is simple. THC and CBD became trapped in the bones after being consumed and absorbed by the blood, before being directed to the bone tissue via the blood capillary system. Between 1638 and 1697, patients who died at the hospital were buried in this crypt, which until now has remained sealed. This rules out any contamination of the site. But can we assume that consumption took place in a strictly medical context?

According to Gaia Giordano, despite its proximity to the old hospital, this is unlikely. Firstly, because there is no mention of the plant in the hospital's detailed pharmacopoeia, suggesting that it was not officially administered by staff. Furthermore, in Western Europe, cannabis was officially banned by the Pope via an edict in 1484. This implies that patients used cannabis either for pleasure or self-medication. But I'm not sure they knew that 300 years later the world would be aware of their little indulgence.