In the 1960s, research surfaced linking psychedelic use to an increased risk of cancer. But a new study published in the Journal of Psychopharmacology found no such link. The researchers studied recent data from a large national survey of Americans and found that psychedelic use (e.g., LSD, MDMA, DMT) was not associated with lifetime cancer development.
Lysergic acid diethylamide (LSD) was first associated with cancer risk when a 1967 study reported chromosomal damage in human white blood cells after exposure. A series of subsequent studies were released suggesting that LSD may have carcinogenic potential, and case reports of LSD users developing cancer added to this concern.
“Beginning in the late 1960s, concerns were raised by laboratory experiments that LSD and other psychedelics might damage chromosomes and potentially cause hematological cancers such as leukemia and lymphoma,” said study author Brian S. Barnett, an assistant professor of psychiatry at the Cleveland Clinic Lerner College of Medicine of Case Western Reserve University.
“Once a potential connection between psychedelics and cancer was reported by the media, it became an important factor in psychedelics becoming Schedule 1 drugs and research into their therapeutic applications coming to an end for nearly half a century.”
However, multiple flaws have been identified in the concepts and methodologies of these early studies. For example, many of them tested LSD concentrations and durations of exposure that far exceeded reasonable dosages of LSD. Additionally, many studies did not control for use of other drugs alongside LSD.
Today, most of the available evidence suggests that psychedelics do not pose a carcinogenic risk. But Barnett and his colleagues note that research in this area largely faded out with the 70s. Now that much more epidemiological data is available, the researchers aimed to revisit and clarify the link between psychedelics and cancer risk. This topic is particularly relevant, the authors say, in light of the ongoing discussion regarding the therapeutic potential of psychedelics.
“With psychedelics now moving rapidly toward FDA approval as medications, I thought it would be interesting to use data from a U.S. government survey of tens of thousands Americans about drug use and health problems to investigate this safety question and see if there actually is any association between psychedelic use and cancer,” Barnett explained.
The researchers aimed to expand upon a 2021 population-level study by Simonsson and associates, which explored the link between lifetime psychedelic use and cancer diagnosis in the past 12 months. For the current study, the researchers explored associations between lifetime psychedelic use and lifetime cancer diagnosis. They also differentiated between cancer of any kind and hematologic cancers (e.g., leukemia, lymphoma).
Barnett and his team analyzed data from the 2015–2019 editions of the National Survey on Drug Use and Health, a nationally representative survey of Americans. Focusing on participants aged 18 and older, the final sample included 210,021 respondents. Importantly, the survey included data on a large number of confounding variables — such as age, sex, race/ethnicity, income, educational attainment, lifetime history of HIV/AIDS, and other drug use.
When controlling for confounding variables, the results revealed that lifetime psychedelic use was not associated with lifetime cancer diagnosis nor hematologic cancer diagnosis. This was true for each of the three classifications of psychedelics: tryptamine (5-MeO-DIPT, AMT, DMT), lysergamide (LSD), and phenethylamine (2C-B, mescaline, MDMA, peyote, and San Pedro).
Interestingly, when researchers did not control for confounding variables, they found that lifetime psychedelic use was associated with a lower prevalence of lifetime cancer diagnosis. The authors suggest that this association may have been driven by the lower age of respondents who reported lifetime psychedelic use.
The authors said results support the findings of Simonsson and colleagues (2021), which revealed no significant link between psychedelic use and cancer diagnosis in the past 12 months. The current study extended these findings to include lifetime diagnosis of cancer and hematologic cancer.
However, “every scientific study has limitations,” Barnett noted. “While it is unlikely that the limitations of this study would change the outcome, it’s important to know that the dataset used for the study does not provide information on the number of times participants used psychedelics (we only knew who used them during their lifetime), doses of psychedelics used, and whether participants’ psychedelic use preceded their cancer diagnosis or vice versa.”
The authors said that more research will be necessary to better understand the physiological safety of psychedelics. “Future research in this area would benefit from employing more detailed epidemiological data,” the authors wrote, “including age of first use for each psychedelic, number of lifetime uses of each psychedelic, time since last use of each psychedelic, age at each type of cancer diagnosis, and information about use of less well-known psychedelics that are gaining increased societal attention, such as ibogaine and ayahuasca.”
The study, “Is psychedelic use associated with cancer?: Interrogating a half-century-old claim using contemporary population-level data“, was authored by Brian S Barnett, Kathleen Ziegler, Rick Doblin, and Andrew D Carlo.