Cannabis Potency: How Did Marijuana Become So Strong?

Once upon a time, cannabis typically weighed in with a THC content of about 10-12 percent. Now, designer strains regularly top 20 percent, with some reaching as high as 28-30 percent THC. The evolution of marijuana over the past few decades is undeniable. Today, there are more super-strains available for medical and recreational consumers than ever before. So how did cannabis become so potent?

Legalization has brought growing out of the basement and into the public eye. And for the first time, growers can lawfully and openly create the optimal conditions for growing super-strong herb. Also, when it’s legal to study, grow, and sell cannabis, locally bred strains tend to thrive. Those locally bred strains are optimized for local growing conditions. This makes them stronger than plants that were produced internationally. the growth in potency has been happening for a few decades. By contrast, wide-scale legalization is only a recent phenomenon.

As technology advances, it becomes more affordable and accessible. More people can take advantage of it than ever before. The same goes for cannabis growers. Advancements in hydroponics systems and artificial lighting technologies, even small things like the humble compact fluorescent light bulb, make growing potent pot easier than ever. You don’t need an industrial grow operation to cultivate killer cannabis these days.

Still, there’s one undeniable factor that has fueled the explosion in potent cannabis strains. Consumer demand. On both the legal and illegal side of things, consumer demand ultimately leads to more potent cannabis. Cannabis prohibition encourages producers to increase profit by reducing the size and volume of their shipments. Concentrating THC in plants makes sense.

On the legal side, however, consumers are looking for products that pack in more of the desired effects. In this case, edibles and other concentrates that mean a consumer has to buy and smoke less cannabis to get the same results are sought after.

The way marijuana is grown can affect the amount of THC in the plant, and therefore its potency. Cannabis sativa is the species of plant that most commonly produces the drugs known as marijuana, hash, or hashish. Normally, the male cannabis plant fertilizes the female plant. If female plants are grown in isolation, then the flowering tops of the plant remain unfertilized. These unfertilized flowering tops, known as “sinsemilla,” have particularly high THC levels. Crossbreeding and genetic modification can also produce strains of the cannabis plant with particularly high levels of THC.

Some argue that cannabis grown hydroponically, or under artificial light, is stronger than cannabis grown outdoors in natural light. Because the amount and quality of resin produced depends on temperature, humidity, light, and soil acidity, cannabis grown outdoors varies considerably in potency, whereas intensive indoor cultivation, often done with female plants and clones, under artificial light, and without soil, produces optimized cultivation conditions and cannabis of a consistently higher potency (UNODC, 2009). Some users of the drug say they can tell when they are using “hydro” cannabis versus “bush weed” because the effects are so much stronger. However, some people do not believe it is hydroponic cultivation itself that makes cannabis stronger; large scale hydroponic cultivators may simply be more likely to use more potent strains and grow plants to their full potential.

Cannabidiol (CBD) content, on the other hand, has shrunk over time. Researchers have been interested in its use in treating schizophrenia, Huntington’s disease, and Alzheimer’s disease, among other brain and mood disorders. It’s been said to have antipsychotic effects and to counter the occasionally psychotic effects of THC. So the fact that it’s being bred out may mean that the high one gets from smoking pot isn’t going to vary a lot, despite what sellers may tell you. And it may mean that people who rely on CBD for medicinal properties, aren’t getting much of that either. Finally, the lab tested for contaminants of both the biological and chemical varieties – i.e., anything from microbes to solvents. And the team found a few: “It’s pretty startling just how dirty a lot of this stuff is,” he says. “You’ll see a marijuana bud that looks beautiful. And then we run it through a biological assay, and we see that it’s covered in fungi.” The team also found butane on some of the samples, which is used to make products like “wax,” an extremely high-potency marijuana.

The biological contaminants aren’t too surprising, since after all, pot is a plant. But contaminants in general may point to the need for some determinations about what’s safe and what’s not.

The rise in THC content has been going on for years – previous research has also found the same patterns – but the steepness of the rise may be greater than expected. So how much does this affect the general public? That part is up for debate.

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“Although the rise in the concentration of THC is not a concern per se, the variability makes it more difficult to titrate the dose to the correct effect,” says Lewis Nelson, Professor and Vice Chair for Academic Affairs at NYU’s Department of Emergency Medicine and Director, of Medical Toxicology Fellowship at the New York City Poison Control Center. “This means that users are more likely to consume excessive doses, leading to adverse clinical effects. This has been seen already in Colorado emergency departments.”

[Updated, originally published 11. 7. 2017]

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