Is Cannabis Getting Stronger? Chromatography Explores!

Cannabis is the most widely used illicit drug in the world — although if more law makers follow the lead set by Colorado that situation could change. But as the law on cannabis changes — is the cannabis itself changing and becoming stronger? Are people getting more bang for their bucks?

A report published in the journal Biological Psychiatry — Changes in Cannabis Potency Over the Last 2 Decades (1995–2014): Analysis of Current Data in the United States — suggests that cannabis is becoming stronger and that this could have consequences for users, particularly among adolescents. Let’s take a look at the report and see what this means for cannabis users.

THC and GC-FID

The study looked at over 38,000 samples of marijuana that had been seized by the United States Drug Enforcement Agency between January 1995 and December 2014. Cannabis potency is usually expressed as the concentration of THC (tetrahydrocannabinol) — the main psychoactive ingredient — in the sample. Although cannabis contains over 500 different compounds in many different chemical classes, it is the cannabinoids and in particular THC that is measured for potency.

There are different cannabis (the plant) preparations found in the marketplace — including marijuana, hash and sinsemilla — but all contain THC. The samples that the team analysed were mainly cannabis plant material (marijuana and sinsemilla), but some samples of hash (the resinous part of the plant) were also analysed. They noted an increase in sinsemilla (a potent seedless female form of cannabis) in recent years.

The team used gas chromatography — with flame ionisation detector (GC-FID) to analyse the samples for cannabinoids. The FID is the most commonly used detector in GC. It’s relatively cheap operating costs combined with its linearity and detection range makes it an ideal detector for hydrocarbons as discussed in the article, The Benefits of Thermal Desorption Coupled with Gas Chromatography for the Analysis of Hydrocarbon Residues in Liquefied Petroleum Gas.

Growing pot potency

The results of the team’s analysis show that the concentration of THC in the samples went from 4 percent in 1995 to 12 percent in 2014. Conversely, an additional component of cannabis that attracts medical interest is cannabidiol (CBD) — it is claimed that CBD may help reduce the symptoms of some illnesses like epilepsy and schizophrenia — fell from 0.21 percent in 2001 to 0.15 percent in 2014. This reduction is possibly due to growers changing cultivation conditions to increase the THC level and avoid detection — growing indoors under artificial lights reduces the CBD concentration.

But some commentators suggest that the increased potency might not mean cannabis users are more at risk from the effects of THC. It is possible that with an increased potency users will reduce the quantity of cannabis, inhale for a shorter period or take fewer hits. Either way, with no quality control in place, the use of cannabis will involve some risk. It is argued by some that legalization — as in Colorado — allows users to reduce the risk of harm by making informed choices.