Kaiser Permanente study suggests higher risk of later hypertension, coronary heart disease
An analysis of nearly 350,000 pregnancies found a higher likelihood of later high blood pressure and coronary heart disease among those who used cannabis before or early in pregnancy.
The study, published in JACC Advances, is consistent with other research suggesting cardiovascular health issues related to cannabis use, though the study authors said more research is needed to understand what the association may mean for patients.
“People with evidence of cannabis use before or during early pregnancy had a higher risk of developing hypertension and coronary heart disease in the years after pregnancy,” said lead author Kelly Young-Wolff, PhD, MPH, a research scientist with the Kaiser Permanente Division of Research (DOR). “This study cannot prove that cannabis caused those outcomes, but the association remained after we accounted for important cardiovascular risk factors, including nicotine and alcohol use.”
The researchers had a unique opportunity to examine cannabis use because the prenatal care process in Kaiser Permanente Northern California includes cannabis screening. This study used data from that screening collected between 2011 and 2023, and followed the patients’ cardiovascular outcomes through 2023, up to 13 years following pregnancy.
They found 12.2% of the patients used cannabis before pregnancy and 6.9% used cannabis during early pregnancy.
Among the cannabis users, the analysis found a 35% increased risk of hypertension and 47% increased risk of coronary heart disease in the years after pregnancy compared with the patients who did not use cannabis. Coronary heart disease includes heart attack, angina, and coronary artery disease.
The researchers did not find a statistically significant increased risk of arrhythmia (abnormal heart beat), stroke, or blood clots in the pregnant patients who used cannabis.
The analysis took into consideration other risk factors for cardiovascular disease, such as smoking tobacco. Of the whole group, 8.7% used nicotine, while nicotine use was more common among just the cannabis users (26.9%). The increased risk of hypertension and coronary heart disease also appeared among pregnant patients who did not use nicotine but did use cannabis.
“The similar findings among patients without evidence of nicotine use suggest that tobacco or other nicotine products do not fully explain the results,” Young-Wolff said. “Still, other factors we could not measure may have influenced the results. We see this as an important signal that warrants more research.”
The study examines a vulnerable population and provides insight to physicians who can use the information to counsel their pregnant patients, said co-author Jamal S. Rana, MD, PhD, a cardiologist with The Permanente Medical Group and DOR adjunct investigator. “There’s not as much awareness about cannabis posing health risks in pregnancy, and this study adds a new dimension to our prevention efforts,” he said.
Other research has suggested that the THC in cannabis can cause inflammation of the endothelial lining of heart arteries, Rana said.
“This study is an important first step in understanding how cannabis use before and during pregnancy may relate to cardiovascular health later on,” Young-Wolff said. “The large cohort and universal prenatal screening give us unusually strong data, but we still need studies that can look at mode of use, frequency, product potency, and changes in cannabis use over time.”
The study is part of a large prenatal cannabis research portfolio at the Division of Research. “Cardiovascular health risks are an important part of our larger prenatal cannabis research effort, and it is good to see useful insights come out of this work,” said senior author Lyndsay Avalos, PhD, a DOR research scientist.
Future research on this topic should look at issues such as the mode of cannabis use, how often it is used, product strength, and the role of screening and education in prevention of related cardiovascular risk, the authors said.
The study was funded by the National Institute on Drug Abuse.
Additional co-authors were Kevin Kong, MPH, Stacey Alexeeff, PhD, and Nina Oberman, MPH, of the Division of Research; and Neal Benowitz, MD, of the University of California, San Francisco.
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About the Kaiser Permanente Division of Research
The Kaiser Permanente Division of Research conducts, publishes, and disseminates epidemiologic and health services research to improve the health and medical care of Kaiser Permanente members and society at large. KPDOR seeks to understand the determinants of illness and well-being and to improve the quality and cost-effectiveness of health care. Currently, DOR’s 720-plus staff, including 73 research and staff scientists, are working on nearly 630 epidemiological and health services research projects. For more information, visit divisionofresearch.kp.org.
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