The success of medical marijuana at alleviating chronic pain could make it a strong contender for chipping away at the American opioid epidemic.

The number of Americans touched by the opioid epidemic has reached alarming proportions. Millions of people are affected each year, and death rates from overdoses have quadrupled since 1999, numbering in the tens of thousands annually, according to the National Institute on Drug Abuse (NIDA). But there may be a less-risky alternative to opioids for alleviating certain types of chronic pain: marijuana.

A growing body of evidence suggests that cannabinoids — chemical components in Cannabis plants or certain synthetic compounds — can be effective in alleviating pain, either alongside or in place of opioids.

As medical marijuana becomes more accessible in the U.S., it could serve as a safer option for some kinds of pain relief and could even help to reduce the number of people addicted to opioids, experts told Live Science. [Marijuana: Facts About Cannabis]

Opioid misuse and dependency have spiked in recent years. Beginning in the late 1990s, doctors began prescribing opioids for pain relief more frequently, following false assurances by pharmaceutical companies that the drugs were not addictive, according to NIDA.

In 2016, opioid-related drug overdoses killed about 116 people every day, with 42,249 people dying from overdoses that year and some 11 million people misusing prescription opioids, according to the U.S. Department of Health and Human Services.

Generally prescribed for severe pain, opioids — a family of drugs that bind to opioid receptors in the body and cause feelings of euphoria — are, in fact, highly addictive, and millions of Americans misuse opioids or become dependent on the drugs. Opioids include opiates; though the terms are often used interchangeably, opiates can also refer to a class of opioids that are naturally or synthetically derived from opium.

If people who are addicted lose access to prescription opioids, they may turn to dangerous illegal opioids, such as heroin, Live Science previously reported. But experts say medical marijuana and synthetic cannabinoids have been found to be highly effective for certain types of pain relief and carry a much lower risk of addiction than opioids.

"Our own opiates"

When a person uses marijuana, cannabinoids in the drug bind to cannabinoid receptors in the human body. These receptors are part of an existing pain-mitigation network that produces endocannabinoids — "our own opiates" — and primes the body to be receptive to compounds with a similar chemical makeup, Dr. Donald Abrams, a professor of medicine at the University of California, San Francisco, told Live Science.

"We have this whole system of receptors and endogenous [internal] cannabinoids that are probably present to help us modulate the sensation of pain," Abrams said. "That makes it sort of obvious that other cannabinoids — those that come from plants — could also have some benefit for pain."

THC, or tetrahydrocannabinol, is the cannabinoid in marijuana that is chiefly responsible for the drug's psychoactive effects, and cannabidiol, or CBD, is another active cannabinoid that does not cause feelings of intoxication.

Evidence from clinical studies suggests that cannabis or cannabinoids are effective in mitigating chronic pain, neuropathic pain (pain caused by a disease or injury affecting the nervous system), and involuntary and continuous muscle contractions associated with multiple sclerosis, Dr. Kevin Hill, an associate professor of psychiatry at Harvard Medical School, told Live Science in an email.

In a study published in September 2015 in the journal JAMA, Hill reviewed 74 medical studies on marijuana use for pain relief dating from 1948 to 2015. He found that there were positive results across 24 trials for patients with chronic pain, neuropathic pain and multiple sclerosis. [Marijuana: Effects of Weed on Brain and Body]

Cannabinoids are also highly effective against pain caused by symptoms associated with some cancers, researchers reported in a study published in 2016 in the journal Progress in Neuro-Psychopharmacology & Biological Psychiatry. Indeed, one type of cannabinoid, sold under the brand name Sativex, is approved in Canada for treating pain that accompanies certain cancers, according to the study.

An alternative to opioids

But how do cannabinoids stack up against opioids?

Marijuana has been shown to produce mild dependence in people; cannabinoids affect brain processes that regulate rewards and reward-seeking behavior, much as other addictive substances, such as opioids, do, scientists reported in a study published in 2007 in the journal Dialogues in Clinical Neuroscience.

But unlike opioid dependence, marijuana dependence can generally be reversed through cognitive behavioral therapy and abstinence without debilitating withdrawal symptoms such as vomiting, diarrhea, insomnia and anxiety, according to the study.

Another side effect of opioid use can be cognitive impairment, which may discourage doctors from escalating doses enough to provide adequate pain relief, according to a study published in 2004 in the journal Pain Management Nursing. However, some cannabinoid compounds — those that do not have a psychotropic effect — can enable patients to reduce their pain without feeling "out of it," Abrams told Live Science.

"I've had patients with cancer who've been put on high doses of opiates, and they find they can't communicate with their family," Abrams said. "Once they have effectively weaned themselves off their opiates onto cannabis, they find it much easier to communicate with their loved ones, while also achieving relief of their pain." (Patients should talk to their doctor before switching drugs.) [Medical Marijuana: Benefits, Risks & State Laws]

And a survey of patients who used both opioids and cannabis for pain found that participants reported a higher satisfaction rate with cannabis than with opioides, Amanda Reiman, a medical marijuana researcher and community relations representative for the cannabis brand Flow Kana, reported in a study published in June 2017 in the journal Cannabis and Cannabinoid Research.

In that study and in prior surveys conducted by Reiman, patients reported the same top three reasons why they turned to cannabis over prescription opioids for pain mitigation: a smaller chance of experiencing withdrawal with cannabis, fewer negative side effects, "and that cannabis was more effective than their other medication," according to Reiman, who also previously served as the California policy manager for the Drug Policy Alliance.

Of the 2,897 medical cannabis patients who served as study participants, ninety-seven percent affirmed that cannabis use enabled them to decrease their opioid doses. Furthermore, 81 percent reported that cannabis when used alone was more effective than cannabis combined with opioids, Reiman and her co-authors wrote in the study.

"Individuals that were choosing to use cannabis instead of opiates to treat pain were doing so because they were having these much better experiences," she told Live Science.

In another study, published in 2011 in the journal Clinical Pharmacology and Therapeutics, patients who were using opioids for pain relief were introduced to vaporized cannabis in clinical trials and under controlled conditions. Scientists reported that the subjects' pain was decreased significantly when they used cannabinoids, suggesting that cannabinoids could enable patients to use opioids in lower doses, and thereby experience fewer side effects.

Risks and restrictions

However, there are also risks accompanying the potential medical benefits of cannabinoid use. Some are associated with THC, which in some people can lead to increased anxiety, or worsening psychotic disorders or mood disorders, Hill said. In elderly people, disorientation from THC's effects could increase the risk of falling, Abrams added.

And cannabinoids may not be a safe choice for people with underlying cardiac disease, because the compounds can affect blood pressure and can accelerate heart rate, Abrams said.

Recent legislation reflects a changing national view of marijuana, with the drug now legally available for medical use in 29 states, the District of Columbia, Guam and Puerto Rico, and for recreational use in eight states and the District of Columbia, according to the National Conference of State Legislatures (NCSL). Possessing small amounts of the drug has also been decriminalized in 22 states and the District of Columbia, the NCSL reported.

However, one of the biggest obstacles to the more widespread use of medical marijuana for pain is the drug's accessibility, Reiman told Live Science.

In states that don't allow medical marijuana, "opiates are going to be way easier and less risky to access than cannabis," Reiman said.

Persistent stigma

Even in states where medical marijuana use is legal, persistent stigma can lead patients to hesitate to turn to cannabinoids to treat their pain, Reiman reported in the June 2017 study.

"Though we were surveying medical cannabis patients in the state of California — where there is an active program — a great deal of our respondents said that they would be more likely to use cannabis as a substitute if it were less stigmatized and more readily available," Reiman said.

Similar findings were presented in 2015 in another study, this one published in the Journal of Psychoactive Drugs, in which researchers wrote that "stigma emerged as a primary and recurring issue as it related to both the process of becoming a medical marijuana user, and remaining one."

Study participants reported that their decisions about using medical marijuana were colored by widely accepted stereotypes of all marijuana users as "stoners," and this factored into their decisions about whom they told about their medical marijuana use, according to the study.

"There was obviously that kind of negative stigma of using marijuana that I'd be looked upon as kind of an addict or a drug user more than a patient," one of the subjects responded.

The scientists also noted that when stigma is attached to a patient's medical condition, it can result in the patient receiving lesser-quality health care, and a fear of experiencing that type of discrimination may hold people back when considering the use of medical marijuana — even if they prefer it to opioids.

"There's still a lack of patient protection — the hardest thing about cannabis now is accessing it in a way that doesn't put someone at risk," Reiman said.

Original article on Live Science.