To determine the association between diabetes mellitus (DM) and marijuana use.
Data from the National Health and Nutrition Examination Survey (NHANES III, 1988–1994) conducted by the National Center for Health Statistics of the Centers for Disease Control and Prevention.
The study included participants of the NHANES III, a nationally representative sample of the US population. The total analytic sample was 10 896 adults. The study included four groups (n=10 896): non-marijuana users (61.0%), past marijuana users (30.7%), light (one to four times/month) (5.0%) and heavy (more than five times/month) current marijuana users (3.3%). DM was defined based on self-report or abnormal glycaemic parameters. We analysed data related to demographics, body mass index, smoking status, alcohol use, total serum cholesterol, high-density lipoprotein, triglyceride, serum 25-hydroxy vitamin D, plasma haemoglobin A1c, fasting plasma glucose level and the serum levels of C reactive protein and four additional inflammatory markers as related to marijuana use.
Main outcome measures
OR for DM associated with marijuana use adjusted for potential confounding variables (ie, odds of DM in marijuana users compared with non-marijuana users).
Marijuana users had a lower age-adjusted prevalence of DM compared to non-marijuana users (OR 0.42, 95% CI 0.33 to 0.55; p<0.0001). The prevalence of elevated C reactive protein (>0.5 mg/dl) was significantly higher (p<0.0001) among non-marijuana users (18.9%) than among past (12.7%) or current light (15.8%) or heavy (9.2%) users. In a robust multivariate model controlling for socio-demographic factors, laboratory values and comorbidity, the lower odds of DM among marijuana users was significant (adjusted OR 0.36, 95% CI 0.24 to 0.55; p<0.0001).
Marijuana use was independently associated with a lower prevalence of DM. Further studies are needed to show a direct effect of marijuana on DM.
We hypothesised that the prevalence of DM would be reduced in marijuana users due to the presence of one or more cannabinoids because of their immunomodulatory and anti-inflammatory properties.
Marijuana use was associated with a decreased prevalence of DM.
Prospective studies in rodents and humans are needed to determine a causal relationship between cannabinoid receptor activation and DM.
Until those studies are performed, we do not advocate the use of marijuana in patients at risk for DM.
Strengths and limitations of this study
Population-based national representative sample of the USA.
Marijuana use was based on self-report, and self-report of illicit substances is often underestimated on self-reports. Self-report is subjected to recall bias. However, we expect that recall bias would be similar in those with DM as those without DM and would be unlikely to bias our results.
Although current marijuana users were divided into heavy and light users based on the number of times they reported using marijuana per month, the amount of marijuana consumed, route of consumption (inhaled vs oral), duration of use and time when they quit were not reported.