In research dubbed “remarkable” by an accompanying editorialist, US doctors describe how current users of marijuana appear to have better blood glucose control than never or former users.
Existing cannabis smokers had lower levels of fasting insulin and were less likely to be insulin resistant than nonusers; this finding remained true even when patients with diabetes were excluded in this large sample from the National Health and Nutrition Survey (NHANES) between 2005 and 2010.
Marijuana users also had smaller waist circumferences and higher levels of HDL cholesterol than never users, Elizabeth A. Penner, from the University of Nebraska College of Medicine, Omaha, and colleagues report in their article published onlineMay 16 in the American Journal of Medicine.
“Previous epidemiologic studies have found lower prevalence rates of obesity and diabetes mellitus in marijuana users compared with people who have never used marijuana, suggesting a relationship between cannabinoids and peripheral metabolic processes,” says senior author Murray A. Mittleman, MD, DrPH, from Beth Israel Deaconess Medical Center, Boston, Massachusetts, in a statement. “But ours is the first study to investigate the relationship between marijuana use and fasting insulin, glucose, and insulin resistance.”
In an accompanying commentary, Joseph S. Alpert, MD, from University of Arizona College of Medicine, Tucson, who is also editor-in-chief of the American Journal of Medicine, wonders whether “[Tetrahydrocannabinol] THC will be commonly prescribed in the future for patients with diabetes or metabolic syndrome alongside antidiabetic oral agents or insulin for improved management of this chronic illness.
“Only time will answer this question for us,” he adds. “Nevertheless, what is very clear is that we desperately need a great deal more basic and clinical research into the short- and long-term effects of this agent in a variety of clinical settings, such as cancer, diabetes, and frailty of the elderly.”
Effects Seem to Be Related to Current Use of Cannabis
Ms. Penner and colleagues studied 4657 participants of the observational NHANES database, a nationally representative survey of US adults, who had completed a drug-use questionnaire.
Of these, 579 were current users (had self-reported smoking marijuana or hashish in the past month), 1975 had smoked marijuana in the past but were not current users, and 2103 had never inhaled or ingested marijuana. Fasting insulin and glucose were measured via blood samples following a nine-hour fast, and homeostasis model assessment of insulin resistance (HOMA-IR) was calculated to evaluate insulin resistance.
Glucose levels were lower among current users of marijuana than never users, but this difference ceased to be significant following multivariate adjustment. The researchers also found no significant association between marijuana use and triglyceride levels or systolic or diastolic blood pressure.
But compared with those who had never used cannabis, current users had 16% lower levels of fasting insulin and 17% lower HOMA-IR, findings that remained significant even after multivariate adjustment. They also had 1.63-mg/dL-higher HDL-cholesterol levels, as well as lower waist circumferences, both of which remained significant after adjustment.
And in an analysis also adjusting for body mass index, which the researchers say is a potential mediator of the link between marijuana and cardiometabolic outcomes, the associations were attenuated but remained statistically significant. The results were also not materially different when participants with diabetes mellitus were excluded.
Crucially, the best results were seen in current users of cannabis. “These associations were weaker among those who reported using marijuana at least once, but not in the past 30 days, suggesting that the impact of marijuana use on insulin and insulin resistance exists during periods of recent use,” Ms. Penner and colleagues observe.
These new findings “are indeed remarkable observations that are supported, as the authors note, by basic-science experiments that came to similar conclusions,” Dr. Alpert points out in his editorial.
Call for Much More Research Into Cannabis
With the recent legalization of medical marijuana use in the form of THC in 19 states and the District of Columbia and recreational use in 2 states, “physicians will increasingly encounter marijuana use among their patient populations,” Dr. Alpert adds. There are an estimated 17.4 million current users of marijuana in the United States, with approximately 4.6 million of these smoking it daily or almost daily.
And although there will continue to be debate regarding legislation and current medical use of cannabis, the real problem is that there “a dearth of scientific, pharmacologic, and clinical studies with this agent,” he observes, pointing out that the majority of research that does exist looks at central nervous system effects of marijuana and potential addictive qualities.
“I would like to call on the National Institutes of Health and the Drug Enforcement Administration to collaborate in developing policies to implement solid scientific investigations that would lead to information assisting physicians in the proper use and prescription of THC in its synthetic or herbal form,” he concludes.
The authors and editorialist have reported no relevant financial relationships.