For decades, marijuana growers, sellers, and consumers have classified strains as "indica" or "sativa" to explain the type of effect they would have when consumed.

But that classification system was faulty to begin with, and the advent of molecular testing proved that there is no sense in splitting them up into indica and sativa.

There's not a simple way to create a more accurate system, however, so the indica-sativa dichotomy endures.

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When you enter a marijuana dispensary you're met with sterile white walls and glass-encased counters that hold marijuana flower, vape pens, chocolates, gummies, and other psychoactive goodies.

Whether a dispensary has a menu hung on its wall, a digital list patrons can scroll through on an iPad, or a physical paper booklet they can flip through, these informational materials, at the very least, classify each marijuana strain as an "indica," "sativa," or "hybrid," and may also include information on the effects and THC concentrations of the Sour Diesel strain or the Blue Dream strain, for example.

This setup, adopted by breeders, dispensary owners, and consumers, suggests there's a dichotomy of marijuana types: indica, which is said to physically relax the body and give a sedative effect, and sativa, which is said to be energizing and provide more of a head-high. Hybrid strains are also sold and considered a midway point between indica and sativa marijuana strains.

In reality, no scientific evidence supports this dichotomy because on a molecular level, indica and sativa strains don't have pattern differences that set the two "types" apart from each other. As a result, consumers may inadvertently buy marijuana strains that don't actually align with the perceived effects they're marketed to provide.

Still, consumers and retailers still use the classification system because it's the only one available, which makes pinpointing the best strains for each person's end goal a trial-and-error process.

"In the absence of any other useful system to classify marijuana, strain and indica-sativa dichotomy is all breeders and distributors have, kind of like what Winston Churchill said about democracy," Jeff Chen, the Director of the UCLA Cannabis Research Initiative, told Insider. "It's the worst system invented, but the best we have."

18th-century researchers originally classified cannabis into two species based on the plant's appearance

"So you see a massive mislabeling of strains, which is often unintentional," Pasternack said. Crystal Cox/Business Insider

Researchers now know that on a molecular level, there's no difference between an indica strain and a sativa strain of marijuana, but that wasn't always the case.

In the 18th century, shortly before North American farmers began growing their own cannabis, French biologist Jean Baptiste Lamark proposed a cannabis classification system based on the appearance of the various cannabis plant samples he had been sent from India, according to the journal Cannabinoids.

Through his observations, Lamark decided cannabis indica plants were shorter and firmer stems with thick stubby leaves that grew in alternating patterns, while sativa-type plants were taller with feathery thin leaves. Lamark said each of the two plants, because of their physical traits, had different uses and effects.

Lamark's classification wasn't a perfect approach though, and in the years following, botanists challenged his dichotomy theory, saying there was actually only one cannabis breed, cannabis sativa L, which could adapt and take on various physical traits and provide different brain and body effects, explaining why two cannabis plants can look so different.

But by then, medical professionals interested in the healing properties of cannabis had adopted the sativa and indica dichotomy as a way to make the substance more palatable and less scary-sounding to the mainstream who had become fearful of the mysterious drug.

Still, as new technologies emerged that allowed researchers to examine cannabis at its molecular level, they found even more evidence that the system Lamark created, one that breeders, sellers, and consumers adopted for various reasons over the decades, was inaccurate.

The advent of molecular testing proved the original classification system was inaccurate

A Sour Diesel strain grown in California will smell, look, taste, and cause body reactions that aren't identical to the physical and chemical properties of Sour Diesel grown in Colorado. Crystal Cox/Business Insider

When researchers were finally able to look at cannabis plants on more granular levels, they found the plant's looks weren't everything and using its physical traits to determine its effect was too simplistic of an approach.

According to Chen, scientists realized through molecular testing that there is just one species of cannabis, cannabis sativa L.

The reason it can look and act so differently in the body from strain to strain is because the environment in which the plant is grown can change its flavor and effect profile while maintaining its genetic base. Factors like the temperature, humidity, soil nutrients, sunlight, and altitude can all affect how a person who smokes, vapes, or eats a marijuana product from that strain will physically react, Chen said.

So a Sour Diesel strain grown in California will smell, look, taste, and cause body reactions that aren't identical to the physical and chemical properties of Sour Diesel grown in Colorado.

For that reason, some breeders and sellers have started using terpenes to classify marijuana strains. Terpenes are non-psychoactive organic compounds found in marijuana that play a role in the smell and flavor of each strain, but there are over 100 different ones, meaning this system could be just as complicated as a trial-and-error one.

Jake Pasternack, the CEO of marijuana brand Binske, compares this approach to beer drinking: "I know I like pilsners and am simple when it comes to beer, but I didn't know that until I tried other types of beer."

The marijuana industry lacks a governing body to regulate how strains are created and classified

Marijuana plants growing under special grow lights, at GB Sciences Louisiana, in Baton Rouge, La. Views about medical marijuana appear to be changing across the South, where efforts to legalize it have long been stymied by Bible Belt politics. Medical cannabis is legal now in 33 states, but most Southern states remain among the holdouts. (AP Photo/Gerald Herbert) Associated Press

Unlike the old-world wine industry where grape growers must follow a governing body's strict set of guidelines, there isn't a regulatory agency in the marijuana industry that requires cultivators to name their strains a certain way, Pasternack told Insider.

"So you see a massive mislabelling of strains, which is often unintentional," Pasternack said, because many cultivators get sent their marijuana seeds from a massive seed bank and don't always know the exact chemical compositions of those seeds, which eventually grow into the plants they harvest and sell to dispensaries.

Today, cannabis growers or cultivators also crossbreed certain strains to make their own proprietary blends, further complicating the process for consumers who are on the hunt for a specific marijuana-induced effect.

At Binske, for example, Pasternack and his team will crossbreed six or seven different strains of marijuana to create one-of-a-kind strains that only Binske knows the recipe for and sells.

Pasternack tells a dispensary a couple of the strains his team used to give those retailers a general idea of what they're selling with consumers come into the store asking questions.

The marijuana dichotomy has been debunked, but is still widely used

Scientists realized, through molecular testing, that there is just one species of cannabis, cannabis sativa L. Crystal Cox/Business Insider

Despite the shortcomings of the indica and sativa classification system, the industry and consumers continue to use it when selling and shopping for marijuana.

"It's a tragic comedy in this space," Pasternack said. "The retail establishment wants to keep it as simple as possible for consumers because they're often coming fresh into the space without knowledge" of marijuana.

An unintended result of keeping things simple, however, could be leaving consumers who are eager to experience the pain-relieving or anxiety-decreasing effects of marijuana feeling confused or defeated because they didn't get what they thought they were getting when they asked for an indica or sativa or hybrid.

If a more accurate system existed, that same group of people could more easily come across a life-changing solution, like realizing a particular strain significantly manages their depression symptoms, and decide they no longer need antidepressants, Chen said.

For the time being, Chen and Pasternack both believe a trial-and-error approach, rather than saying you only like indicas or sativas, is the best way for a person to pinpoint the marijuana strains that work well for their needs.