The Impact of Marijuana Use on Glucose, Insulin, and Insulin Resistance among US Adults

Penner EA, Buettner H, Mittleman MA
Am J Med. 2013 May 9. doi: 10.1016/j.amjmed.2013.03.002

Background
Marijuana use prevalence is on the increase in the United States, both for recreational and medicinal use, and physicians will thus increasingly be faced with marijuana use among patients [1,2]. Marijuana use is associated with higher caloric intake [3,4], but also with lower body mass index (BMI) [4] and lower prevalence of obesity [5] and diabetes mellitus [6]. The mechanisms that may explain this paradox are not known.
This study examined the associations between habitual marijuana use and measures of fasting glucose and insulin levels, insulin resistance and components of the metabolic syndrome in 4657 participants of the National Health and Nutrition Examination Survey (NHANES)[7].
Participants were classified as never users (n=2103), past users (smoked marijuana at least once but not in the past 30 days, n=1975) and current users (smoked marijuana at least once in the past 30 days, n=579).

Main results

• In unadjusted analyses, past and current marijuana use were associated with lower levels of fasting insulin, glucose, HOMA-IR (a measure of insulin resistance that combines fasting serum insulin and fasting plasma glucose), BMI and hemoglobin A1c. Current marijuana use was inversely associated with waist circumference.
• After adjustment for age and sex significant associations were seen between past and current use of marijuana with lower levels of fasting insulin, glucose, HOMA-IR and BMI. Current use was associated with higher HDL-C levels and lower waist circumference.
• In comparison with people who reportedly had never used marijuana, current use was associated with 16% lower fasting insulin levels (95%CI: -26 to -6), 17% lower HOMA-IR (95%CI: -27 to -6) and 1.63 mg/dL higher HDL-C levels (95%CI: 0.23-3.04). No significant dose-response relationship was found among current users.
• After adjustment for BMI, associations between current marijuana use and fasting levels of insulin, HOMA-IR and waist circumference were weaker, but remained statistically significant. Exclusion of participants with diabetes mellitus yielded comparable results.

Conclusion
These findings suggest that  marijuana has an impact on insulin and insulin resistance in periods of recent use, since the observed effects of lower fasting insulin and lower insulin resistance were attenuated in past users as compared to current users. Earlier studies in mice and men suggest a relationship between cannabinoid receptor stimulation and insulin sensitivity.
Considering the increasing use of marijuana, physicians should be aware of the effects marijuana can have on common disease processes like diabetes mellitus.

References

1.Results from the 2010 National Survey on Drug Use and Health: Volume I. Summary of National Findings. Rockville, MD: Substance Abuse and Mental Health Services Administration; 2011.
2. State Medical Marijuana Laws. National Conference of State Legislatures. Available at: http://www.ncsl.org/issues-research/health/statemedical-marijuana-laws.aspx. Accessed February 7, 2013.
3. Foltin RW, Fischman MW, Byrne MF. Effects of smoked marijuana on food intake and body weight of humans living in a residential laboratory. Appetite. 1988;11:1-14.
4. Smit E, Crespo CJ. Dietary intake and nutritional status of US adult marijuana users: results from the Third National Health and Nutrition Examination Survey. Public Health Nutr. 2001;4:781-786.
5. Le Strat Y, Le Foll B. Obesity and cannabis use: results from 2 representative national surveys. Am J Epidemiol. 2011;174:929-933.
6. Rajavashisth TB, Shaheen M, Norris KC, et al. Decreased prevalence of diabetes in marijuana users: cross-sectional data from the NationalHealth and Nutrition Examination Survey (NHANES) III. BMJ Open.
2012;2:e000494.
7.National Health and Nutrition Examination Survey, Centers for Disease Control and Prevention. Available at: http://www.cdc.gov/nchs/nhanes/about_nhanes.htm. Accessed September 10, 2012.

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