The number of Americans who smoke, ingest or apply the psychotropic drug has more than doubled in the last decade, but we still don't know much about the plant.
Scientists are getting closer to figuring out which of the many chemicals in cannabis are responsible for different'strains', and why they seem to give people unique highs when combined in different ways.
We didn't know which of the hundreds of cannabinoids give the flower its distinctive scent.
The family of volatile sulfur compounds (VSCs) that make up this odor have not been identified in nature before, but are very similar to garlic.
Terpene, a volatile organic compound, has been found to give cannabis a distinct smell.
Terpenes are often found in other aromatic plants, like lavender and rosemary, but previous research suggests they only contribute about half of cannabis' overall aroma, and there's little evidence linking them to a skunky scent.
Researchers measured and analyzed the various strong-smelling metabolites found in cannabis flowers and also in concentrated cannabis extract to find out the chemical origins of the skunk scent.
The team was looking for VSCs because they are also found in smelly plants like hops and garlic.
The compounds, known as VSC3 through VSC7, all show a similar structural organization to garlic VSCs, as can be seen in the image below.
The compounds in garlic might have health benefits, such as anticarcinogenic properties and improved cardiovascular health.
The authors say that the structural similarities between VSCs in cannabis and garlic warrant further investigation to determine if the former possess similar health benefits to those of the latter.
Four members of a smell-testing panel were used to rate the smell of cannabis flowers and cannabis extracts being researched. The ratings were compared to the chemical make-up of VSCs.
There seems to be a strong correlation between VSC3 concentrations and the smell detected by the panel.
The chemicals in other VSCs were quite different when the smell of a skunk was present.
VSC3 was linked to the smell of the skunk across all the different breeds.
It doesn't mean that VSC3 is the only one with a sulfury smell. The role of these compounds in an odor is complicated and depends on what other VSCs are present.
The panel rated the smell of VSC3 as "mildly reminiscent of a flower", but when the top ten VSCs were added together, the panel rated the smell as "no whiff of sulfur".
Adding VSC3 at a low, 1 percent dilution immediately resulted in a smell change that "strongly mimicked the scent of a flower."
The authors said that the combination of VSCs and other major components combined to yield the scent of cannabis.
When VSC3 and VSC5 are combined at high concentrations, it's interesting. VSC5 tends to make the smell of VSC3 even stronger.
This could help explain why cannabis extract is still quite smelly after being converted into an oil.
When cannabis was grown in a greenhouse, VSCs increased as the plant began to flower. The compounds hit their highest concentrations when the flower was dried out. The concentrations of VSC began to fall a week after storage.
The authors write that the drop in VSC3 concentration suggests rapid volatilization, which most likely contributes to the extremely diffuse and detectable aroma associated with cannabis.
The team hopes that further research can shed light on the potential health benefits of VSCs and the sulfury smell of weed.
The study was published in a journal.