Marijuana, cannabis, weed, pot, ganja, Mary Jane. Call it what you want, it’s still the most commonly used psychotropic–or mind-altering–drug in the United States. In fact, according to the 2018 National Survey on Drug Use and Health, produced by the Substance Abuse and Mental Health Services Administration (SAMHSA), 43.5 million people age 12 and up in the United States reported using marijuana that year, up 15 percent from the previous year.

With marijuana now legal for medicinal use in 33 states and recreational use in 11 states, that number can only be expected to rise, which begs the questions, is marijuana safe? Is it healthy? And what does it actually do to the body?

What Exactly Is Marijuana and How Does it Make You Feel?

According to the National Institute on Drug Abuse (NIDA), “marijuana refers to the dried leaves, flowers, stems and seeds of the Cannabis sativa or Cannabis indica plant.” (It’s the same plant origin as hemp, but hemp has been modified to not contain THC.) These marijuana plants contain THC, the active chemical component that causes mind-altering effects like:

  • Altered senses (for example, seeing brighter colors)
  • Altered sense of time
  • Changes in mood
  • Impaired body movement
  • Difficulty with thinking and problem-solving
  • Impaired memory
  • Hallucinations (when taken in high doses)
  • Delusions (when taken in high doses)
  • Psychosis (risk is highest with regular use of high potency marijuana)

How Long Does Marijuana Stay In Your System?

The effects of marijuana can last for two to ten hours, depending on a few factors:

  • How much you have
  • How much THC it had (concentrates, or extracts, that you vape are among the most potent forms of weed)
  • Your body weight and body fat
  • Your metabolism
  • Whether or not you’ve eaten
  • Whether or not you have a tolerance

But well past the time you feel the high, marijuana can still be in your system, even up to 90 days, depending on how often or how much marijuana you use.  There are two factors that affect detection: if you’re a regular user and the kind of test. For example, hair tests are the most sensitive. Here’s what the studies have shown:

  • First time smokers: Tests may detect it for about 3 days.
  • Someone who smokes marijuana three or four times per week: Tests may detect it for 5–7 days.
  • Daily smokers: Tests may detect it in for 30+ days.

As far as how sensitive each type of test is, here they are in order of how long they can detect marijuana in your system:

  1. Hair tests are the most sensitive tests, detecting THC for up to 90 days after use. They’re also known for false positives.
  2. Urine tests can detect marijuana for 3–30 days after use.
  3. Saliva tests can detect marijuana for approximately 24 hours after use, but some can pick it up even up to 72 hours.
  4. Blood tests can only detect THC for a few hours.

Are There Risks to Using Marijuana?

“Many people think of cannabis as low risk, which can be true, but people like psychiatrists that say it’s harmful are also right. It can be not too harmful for people who have low risk for other mental health disorders and who use it less frequently, but it can be dangerous for people with risk factors and those who use it more frequently,” explains Jasleen Chhatwal, MD, chief medical officer and director of the Mood Recovery Program at Sierra Tucson, a leading residential and outpatient treatment center for substance abuse disorders, trauma-related issues, chronic pain, mood and anxiety, and other co-occurring disorders.

“Risk factors for adverse mental health effects are family risk of depression, depression with psychosis, bipolar disorder. These people are at higher risk of these conditions already. Marijuana can precipitate that,” she says. “Another thing we notice is that the younger people are when they start using marijuana, the riskier it can be, particularly for adolescents whose brain is still developing. Research has shown a general decline in IQ, understanding or knowledge as well as verbal language.”

Marijuana: A “Gateway” Drug?

While some call marijuana “a gateway drug,” increasing the likelihood of trying other drugs, others insist you can’t be addicted to marijuana, and you certainly can’t overdose on it like you can other illicit drugs. Dr. Chhatwal agrees that overdose resulting in death has not occurred, but marijuana does affect the brain’s addiction center, potentially leading to other drug use and dependence.

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“Yes, you can be addicted to marijuana. In fact, almost 30 percent of people who use marijuana meet the criteria for cannabis use disorder, which is how we determine dependence,” she says. “When we talk about dependence–or addiction–we mean that you feel like you need to take it to function, you need to take higher amounts to achieve the same effects, and when you stop you feel withdrawal. We talk about the amount of time you spend thinking about it and the time spent trying to procure it. We are seeing that kind of dependence occurs in people who use it more consistently. The higher the potency, the stronger the withdrawal symptoms, such as difficulty sleeping, irritability, loss of appetite or nausea, restlessness.”

So What About Medical Marijuana?

While marijuana has been legalized for medicinal use in 33 states, the drug is still classified by the Food and Drug Administration and the Drug Enforcement Administration among other Class 1 substances with no proven medical uses. Such classification has limited research and kept marijuana federally illegal. Still, while the medicinal benefits of THC remain controversial, the benefits of CBD, or cannabidiol, the non-intoxicating component of the cannabis plant, have been more widely accepted.

Marijuana products have been found to provide a wide variety of benefits, from pain control and stress management to the treatment of seizures and PTSD.

“There are pretty clear areas in medicine–non-mental health–where marijuana has been found to be beneficial,” Dr. Chhatwal says. “For example, relieving nausea from chemotherapy and muscle spasms from degenerative diseases, relief from irritable bowel syndrome and other gastrointestinal discomfort, and improvement in appetite, which makes it useful in end-of-life care.”

The problem, she adds, is that research on these benefits is small, and much more needs to be done over a longer time period to fully understand the risk versus the reward.

Marijuana: Risk vs. Reward

“As a physician, I try not to be on either side. Still, seeing cannabis legalized recreationally throughout the country is a little scary for me,” Dr. Chhatwal concludes. “People want an easy answer, and there is no easy answer – we have to do a risk-benefit analysis and do our due diligence. I don’t even prescribe ibuprofen to people and say take as much as you want!

“When it comes to marijuana it needs to be the same way. We have to do long-term research and there has to be a safety net,” she continues. “People are thinking it’s a panacea because it grows out of the ground, but the truth is, you can’t eat everything that grows out of the ground.”

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Last Updated: May 27, 2021