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Whether you’ve used it yourself, have a friend who tokes, or don’t know anyone who is canna-curious, you probably have an opinion about weed.

Cannabis — as in, the name of the plant that produces marijuana and the substance itself — is no longer considered as taboo as it once was. In fact, 14 percent of American adults have used marijuana in the last year. That’s roughly the same number of people who smoke cigarettes.Keyhani S, et al. (2018). Risks and benefits of marijuana use: A national survey of U.S. adults. DOI: 10.7326/M18-0810

Before it became illegal, cannabis was long used as a medicine. The U.S. government officially criminalized cannabis in 1937, and use quickly declined after that.Zuardi AW, et al. (2006). History of cannabis as a medicine: A review. DOI: 10.1590/S1516-44462006000200015][Abuhasira R, et al. (2018). Medical use of cannabis and cannabinoids containing products – Regulations in Europe and North America. DOI: 10.1016/j.ejim.2018.01.001

Now, with a resurgence in marijuana as medicine and the ever-changing legal landscape, it’s helpful to know about how it works. Here’s what actually happens to your brain and body on cannabis.

You typically hear about two types of cannabis: C. sativa and C. indica. They work in similar ways, with some notable differences.Sawler J, et al. (2015). The genetic structure of marijuana and hemp. DOI: 10.1371/journal.pone.0133292

Cannabis plants produce chemical compounds called cannabinoids. More than 100 unique cannabinoids have been identified in different strains of the cannabis plant. The ones that get the most attention are delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD).Lafaye G. (2017).Cannabis, cannabinoids, and health. https://www.ncbi.nlm.nih.gov/pubmed/29302228

“THC is the most psychoactive compound,” says Thorsten Rudroff, PhD, an assistant professor at the University of Iowa who has studied cannabis for multiple sclerosis. “When you smoke cannabis, THC gives you the high feeling. The more THC you have, the more powerful the high.”

The specific effects differ from person to person, but a few are common. “You’re more sensitive to sound; you’re hungrier,” says Beatriz Carlini, PhD, an affiliate associate professor and research scientist at the University of Washington.

“All those different sensations that people who use marijuana recreationally describe — like being more relaxed — are because of the THC.” It also increases dopamine levels, creating that sense of euphoria.Oleson EB, et al. (2012). A brain on cannabinoids: The role of dopamine release in reward seeking. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3405830/

You know that time you thought you smelled a skunk, but it turned out to be someone smoking a J nearby? Those are the terpenes at work.

Terpenes are the compounds responsible for the plant’s unmistakable odor. But recently researchers have found that they can do a whole lot more than that. It turns out that terpenes play a role in how weed hits you.

More research is needed, but scientists have an inkling that terpenes can impact THC’s effects related to pain, anxiety, appetite disorders, and more. It’s looking more and more like a synergistic relationship.Russo EB, et al. (2017). Chapter 3: Cannabis pharmacology: The usual suspects and a few promising leads. Cannabinoid Pharmacology. DOI: 10.1016/bs.apha.2017.03.004

CBD, on the other hand, is a different cannabinoid that acts as an antagonist to THC, Rudroff says.

“CBD does not have psychoactive effects, but it does have beneficial effects,” he says. “It reduces pain and muscle spasticity [stiffness] and can make you more relaxed. This is the compound of greatest interest for medical marijuana.”

You’ve probably noticed how hot CBD products are right now. Sales are expected to reach $22 billion in the next 3 years. Well-known pro athletes like Rob Gronkowski and Lamar Odom are pursuing endorsements or business deals with CBD companies.

“You can look at this and say, ‘THC is bad, and CBD is good,’ but it’s not that simple,” Rudroff says. “There are some interactions. You need both in the product to work together.” Scientists are still working out the perfect ratio, but Rudroff says some research suggests it might be 1-to-1.

The legal status of cannabis means it’s difficult to fully understand the benefits of CBD. In July 2019, the FDA released a consumer update saying they are “working to learn more about the safety of CBD,” but CBD products are not approved.

In August 2019, Senate Majority Leader Mitch McConnell put pressure on the FDA to move faster, proposing an amendment that would force them to implement guidance on CBD products in the next 120 days.

First, a quick neuroscience lesson: Your brain is made up of billions of neurons and neural circuits. Neurons are long cells that are clustered near each other with a tiny space between their active sites.

To bridge the gap (or synapse) between neighboring neurons, chemicals called neurotransmitters deliver messages by traveling from one neuron to another. They then attach to molecules called receptors. Your body has many types, including endocannabinoid receptors.

“When we experience pain, inflammation, or stress — or have issues related to fear or mood — our body releases a number of neurotransmitters. Sometimes [endocannabinoids], which go to our endocannabinoid system are released to modulate these sensations as well,” Carlini says.Piomelli D. (2005). The endocannabinoid system: A drug discovery perspective. http://europepmc.org/abstract/med/16044662

Since the cannabinoids in marijuana look and act the same as the kind your body makes, they latch on to the cannabinoid receptors in your brain. There are two known types.

First up, CB1 cannabinoids are (mostly) located in parts of your brain associated with learning, memory, reward, anxiety, pain, and movement control. Then there are the CB2 cannabinoids, which are associated with your immune system.Ameri A. (1999). The effects of cannabinoids on the brain. DOI: 10.1016/S0301-0082(98)00087-2 Priyamvada S, et al. (2012). Chemistry, metabolism, and toxicology of cannabis: Clinical implications. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3570572/ Alger BE. (2013). Getting high on the endocannabinoid system. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3997295/

The exogenous cannabinoids throw your usual neuron functions out of whack, boosting certain signals and interfering with others. That’s why marijuana’s effects can range from a feeling of relaxation and pain relief to clumsiness, anxiety (or lack thereof), and even the munchies.

Just how quickly do you feel those results? Well, it all depends on whether you smoke, vape, or consume edibles.

“When you smoke, [cannabis] enters the bloodstream very quickly,” Rudroff says. “When you eat it, it can take up to 20 or 30 minutes before you can feel the effect.”

How long it takes also depends on the concentration of THC and CBD in the product you’re taking. “For us as scientists, it’s all about the levels of THC and CBD,” Carlini says. “It’s very hard to say, ‘Purple Haze [a popular strain of weed] is sativa, and it has X effect.’”

Weed experiences vary from person to person. What produces paranoia in one person might not have the same effects in someone else. The NIH says you can expect these side effects, among others:

  • altered senses
  • distorted sense of time
  • changes in mood
  • impaired body movement
  • difficulty with problem solving
  • impaired memory

Science can explain certain feelings like muscle relaxation and hunger, but the exact formula needed to create an identical reaction in everyone? That’s a lot trickier.

“We don’t doubt the differences, it’s just not well understood from the perspective of science,” Carlini says. “It’s a very complex plant.”

And strains aren’t as clear-cut as they used to be. You’ve probably heard that sativa strains can make you feel like you’re on cloud nine or ready to create a masterpiece, while indica strains are good for ditching PMS pain or catching some much-needed Zzz’s.

But recently researchers have started questioning conventional wisdom on strains. “The whole thing about strains is that we have no scientific basis that they will produce different experiences,” Carlini says.

She and Rudroff both say this is due to the amount of crossbreeding that has happened. At this stage, it’s tough to track botanical origins. That’s not to say science can’t pin down any effects. For instance, if you’ve ever smoked pot and felt anxious, it’s likely you smoked a strain with a high level of THC.

“Doses that are THC dominant can provoke paranoia,” Carlini says, “but good luck on having an equation on when that is going to happen.”

As for the consequences of habitual pot use, the jury is out. One recent study found that using pot regularly for 20 years resulted in higher incidences of gum disease but not much else.Hill KP, et al. (2016). Minimal physical health risk associated with long-term cannabis use — but buyer beware. DOI: 10.1001/jama.2016.5181

Another study that measured cognitive performance found that middle-aged users had poorer verbal memory than their non-using counterparts.Hall W, et al. (2016). Long-term marijuana use and cognitive impairment in middle age. DOI: 10.1001/jamainternmed.2015.7850

At this point we can’t be sure how reliable the data is. Many long-term studies like these use self-reporting techniques, which aren’t always dependable.

“We don’t know much about the long-term effects of cannabis,” Rudroff says. “In my opinion, cannabis does not lead to physical and mental dependence as long as it is used in a responsible manner.”

However, Rudroff adds that effects seem to be highly dependent on the age at which you start using. He says people who start at a younger age — when the brain is not fully developed — may have more negative effects later in life.

Researchers have only scratched the surface of this powerful plant. It’s getting a buzz (see what we did there?) for its potential to do everything from relieve pain to treat cancer symptoms, but a lot still isn’t known.

That said, canna-culture seems to be on everyone’s radar these days, from topicals to tinctures, edibles to extracts. If you decide to indulge, we recommend you do so responsibly. Everyone has a different sweet spot. Start slow and get to know the dose that works for you.