Updated 6/10/19

Each year, surgeons perform over 100,000 kidney, liver, and other solid organ transplants. Every 12 minutes, a new person is added to the organ transplant waiting list, and every day, 21 people die waiting for an organ match.

As more patients have turned to medical cannabis to treat their conditions, that choice has put the patient in a catch 22 situation.

Despite the high number of organ placements, recipient demand for donor organs still far outweighs the available supply. Nearly 120,000 patients are waiting for an organ, and in many cases, patients wait over a year for a match. The donor-recipient matching process for liver, kidney, and other organ transplants is very complex. Physicians consider many parameters, like disease progression and the patient’s functional status. An ideal match minimizes organ rejection while maximizing the patient’s long-term survival.

Organ donors and recipients have traditionally not been selected if they use cannabis. As more patients have turned to medical cannabis to treat their conditions, that choice has put the patient in a catch 22 situation: the very remedy that brings relief is also likely the reason for removal from the organ wait list. The same goes for organ donors.

Who Decides?

In the United States, two groups oversee organ donation: the Centers for Medicare and Medicaid Services (CMS) and the United Network for Organ Sharing (UNOS). UNOS policies strive to match donor organs with transplant candidates in ways that save as many lives as possible and provide transplant recipients with the best possible chances for long-term survival.

UNOS only considers criteria based on medicine or logistics; they do not consider social characteristics like income, insurance coverage or lifestyle choices. Together, UNOS and the CMS set organ donation criteria and accredit transplant hospitals around the nation. Additionally, the nation’s Organ Procurement Organizations (OPO), a network of 58 federally-designated centers across the country and territories, has the role of evaluating deceased organ donors, data which UNOS and CMS consider in future organ allocation criteria.

Accredited transplant hospitals provide their inclusion and exclusion criteria to CMS for review and approval. Patients are evaluated on multiple factors including surgical, medical, and psychosocial risks. Transplant centers are held to extremely high standards designed to achieve outcomes that exceed expectations at the 1- and 3-year post-surgery milestones.

As such, transplant hospital medical directors can and often do set more stringent donor-recipient criteria. While all OPOs hospitals strictly adhere to ensuring there is no racial or gender discrimination in the process, OPO medical directors otherwise have free reign to use any other criteria as a disqualifying factor. While some hospitals are stricter than others, certain hospitals also take on riskier patients, such as patients who have a higher cardiac risk.

Why Does Cannabis Not Mix?

Many transplant centers have living donor programs and are required to have CMS-evaluated stringent protocols regarding how they evaluate living donors. These donors undergo an extensive evaluation, which includes an independent living evaluation and a psychosocial evaluation, both required by both UNOS and CMS.

While transplant programs across the country have different rules regarding marijuana use in a living donor, most treat marijuana use the same way they treat tobacco use. Both are a risk, and donors are asked to demonstrate a stopped use for 30 days.

Cannabis may also interact with immunosuppressant drugs given post-transplant. Smokers have increased risk of lung infections, and since transplant candidates already have compromised immune systems, doctors say cannabis use can significantly increase the risk of contracting deadly Aspergillosis fungal infections during the transplant process.

“How much risk does cannabis really pose versus the benefit that the patient potentially gets from getting the transplant?” David Klassen, Chief Medical Officer at UNOS

Maine is an example of more stringent transplant criteria. After two organ recipients who were cannabis smokers died from the fungal infection, Maine enacted a policy to remove cannabis consumers from the waitlist. Once cannabis-free, they can be added back in.

In an interview with CNN, UNOS chief medical officer Dr. David Klassen said that while Aspergillosis is a devastating complication of any transplant, how often is it really linked to cannabis use? Klassen described it as a matter of cost-benefit: “How much risk does cannabis really pose versus the benefit that the patient potentially gets from getting the transplant?”

Is the Tide Turning?

Indeed, Klassen’s question is the question, and more hopsitals realize the need for a consistent answer.

In a recent journal publication entitled “Marijuana use in transplantation: a call for clarity,” researchers cited the variation among transplant hospitals regarding cannabis policies as reported in the results of a survey sent to the American Society of Transplantation (AST) membership. The survey was designed to compare policies with actual observed complications clearly attributed to cannabis use. About 8% of the AST membership responded, noting tremendous variations in transplant approval processes—some even had wide policy differences within a single hospital. Respondents also noted a big disconnect between perceived risk of medical cannabis use and actual observed complications.

In another survey, researchers reported a lack of “consensus among experts regarding marijuana use in transplantation patients.” While the team cited a few individual case reports of kidney and heart complications as well as drug interaction issues like tacrolimus toxicity, the researchers also cited studies that show no difference in survival rates of cannabis users versus non-users, like the ones below.

Liver Transplants

Does cannabis use affect the outcome of a liver transplant? This research team looked retrospectively at nearly 1,000 adults who were evaluated for liver transplant at a large medical center. Patients could not be current cannabis consumers to be placed on the list, and prior cannabis use was either self-reported by patients or validated in urine tests. The prevalence of cannabis use in these patients was nearly 50%, and was not associated with worse outcomes on the transplant list. The same cannot be said of illicit drug use.

It seems that transplant hospitals may be trending—albeit slowly—toward including cannabis as one of many holistic evaluation criteria rather than a standalone exclusion. 100 UNOS-approved liver transplant programs were questioned about liver transplants, typically needed by patients with either advanced hepatitis or alcoholic liver disease. Most programs require candidates to be “substance-abstinent” for at least six months before being considered for a donor organ.

About half of the programs responded to the survey, stating that about 28% of patients used cannabis but were required to discontinue use prior to surgery. About 14% had active cannabis consumers as transplant patients. These researchers noted that policies for cannabis, alcohol, and even drug use have become more flexible but remain highly variable across the country.

Heart & Lung Transplants

The heart and lung transplant institutions also have no consensus regarding cannabis use, and for that matter, neither do physicians around the globe. This team conducted an international survey of 360 heart transplant providers from 26 countries, and found that 64% of respondents favored placement of advanced, end-stage heart failure patients on the transplant list even if they had used legal cannabis. Only about 27% favored list placement of recreational cannabis consumers. Most organ providers (68%) required the cannabis abstinence period.

Researchers who have delved into the issue show that these policies are driven largely by attitude and case reports rather than by a large body of scientific evidence. Science has shown that cannabis smokers are at increased risk of lung infections, emphysema, and lung cancer, but should the person be considered a bad organ donor choice?

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This research team says no. They looked at six years of retrospective data to answer that question, and found no evidence that cannabis use affected lung donor organ viability. There was no difference in patient outcomes regarding lungs from healthy donors and lungs from cannabis smokers.

Publicity of cases in which the organ donation process has failed a patient only add fuel to the fire, like the case of 19-year-old Riley Hancey, who was denied a double lung transplant in his home state of Utah. Hancey contracted a severe form of pneumonia that left both lungs scarred and collapsed, yet he tested positive for THC and was denied a slot on the transplant list. Months later, Hancey’s parents successfully got their son the operation in Pennsylvania, but his body was too weak and he died shortly after surgery.

In the same CNN interview, Dr. James Whiting, surgical director of the transplant program at Maine Medical Center said that the transplant community’s goal is of course to use as many organs as possible. “That’s why we’re here. So when we turn someone down, it’s a personal failure in many ways.” Whiting told CNN that conversations regarding medical marijuana use are ongoing, and that he feels that doctors will find a way for people who use cannabis to be listed and transplanted.

Kidney Transplants

Another research team looked at retrospective single-institution kidney transplant data from 2000 to 2016. Donors and recipients were divided into cannabis and non-cannabis groups, and their outcomes were compared. There were no noticeable differences in patient outcomes; in fact, long-term kidney function was nearly identical. The researchers concluded that studies like theirs could help increase the donor organ pool, and they hope their published results will add to the ongoing conversation.

Should Higher-Risk Donors Be Considered?

Given the demand for organs and longer waitlists, some governments like the UK are considering higher-risk organ donations for patients in extreme need who would otherwise not get a transplant. UK data shows that nearly 25% of patients in the decade between 2005 and 2015 died waiting for a transplant, so the National Health Service is looking into alternate donors for patients with debilitating lung conditions like cystic fibrosis and COPD/emphysema.

The risk, particularly for lung cases, is much higher in the UK where consumers tend to smoke both cannabis and tobacco. In contrast, Americans tend to smoke only cannabis. There are definitely two sides to the coin. In the case of lung transplants, why would a recipient want an organ exposed to the same harms as the diseased lung the patient is receiving the transplant for?

However, as of yet, there is no scientific evidence linking lung cancer to cannabis consumption, so people on the waitlist might be willing to take a higher-risk organ, given the alternative.

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Jacqueline Havelka Jacqueline Havelka is a contributing writer for Leafly. She's a rocket scientist turned writer, having worked in the space program for many years managing experiments on the Space Station and Shuttle. Jacqueline currently owns her own firm, Inform Scientific, specializing in technical and medical writing and research program management. When she’s not writing, she is likely watching college football. View Jacqueline Havelka's articles