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Marijuana Use in Models for Health Outcomes

  • Christin A. Thompson
    Affiliations
    Department of Clinical Pharmacy, Pharmaceutical Economics & Policy, Leonard Schaeffer Center for Health Policy & Economics, University of Southern California, University Park Campus, Los Angeles
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  • Joel W. Hay
    Affiliations
    Department of Clinical Pharmacy, Pharmaceutical Economics & Policy, Leonard Schaeffer Center for Health Policy & Economics, University of Southern California, University Park Campus, Los Angeles
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      To the Editor:
      Using data from the continuous National Health and Nutrition Examination Survey (NHANES) to estimate the effects of current and past marijuana use on certain health outcomes associated with an increased risk of diabetes and cardiovascular disease,
      • Alberti K.G.
      • Zimmet P.
      • Shaw J.
      The metabolic syndrome—a new worldwide definition.
      Penner et al
      • Penner E.A.
      • Buettner H.
      • Mittleman M.A.
      The impact of marijuana use on glucose, insulin, and insulin resistance among US adults.
      found that marijuana users experienced improved insulin resistance, higher high-density lipoprotein cholesterol, lower insulin, lower glucose, and smaller waist circumferences compared with nonusers.
      • Penner E.A.
      • Buettner H.
      • Mittleman M.A.
      The impact of marijuana use on glucose, insulin, and insulin resistance among US adults.
      NHANES captures self-reported marijuana use and cardiometabolic risks at a single point in time for each survey respondent. These data lack behavioral or environmental variables necessary to control for unobserved differences between users and nonusers. Penner et al's
      • Penner E.A.
      • Buettner H.
      • Mittleman M.A.
      The impact of marijuana use on glucose, insulin, and insulin resistance among US adults.
      use of simple regression models to estimate a static relationship between marijuana use and health outcomes ignores unobserved cumulative mediating factors (eg, other drug use, psychological factors, personality, behavioral traits) that may correlate with both marijuana use and cardiometabolic risk factors.
      • French M.T.
      • Popovici I.
      That instrument is lousy! In search of agreement when using instrumental variables estimation in substance use research.
      Statistical analyses that fail to account for such issues are subject to biased parameter estimates and misleading results.
      • Angrist J.D.
      • Pischke J.-S.
      Mostly Harmless Econometrics: An Empiricist's Companion.
      Using the same NHANES data but using other self-reported personal consumption variables in place of marijuana in the Penner et al
      • Penner E.A.
      • Buettner H.
      • Mittleman M.A.
      The impact of marijuana use on glucose, insulin, and insulin resistance among US adults.
      estimation equations, we found that alcohol and carbohydrate consumption had even larger beneficial effects on each of these cardiometabolic risk factors than marijuana; a clearly nonsensical result. If we are to believe Penner et al
      • Penner E.A.
      • Buettner H.
      • Mittleman M.A.
      The impact of marijuana use on glucose, insulin, and insulin resistance among US adults.
      that marijuana use is great for avoiding diabetes and obesity, then beer and pizza are even better.

      References

        • Alberti K.G.
        • Zimmet P.
        • Shaw J.
        The metabolic syndrome—a new worldwide definition.
        Lancet. 2005; 366: 1059-1062
        • Penner E.A.
        • Buettner H.
        • Mittleman M.A.
        The impact of marijuana use on glucose, insulin, and insulin resistance among US adults.
        Am J Med. 2013; 126: 583-589
        • French M.T.
        • Popovici I.
        That instrument is lousy! In search of agreement when using instrumental variables estimation in substance use research.
        Health Econ. 2011; 20: 127-146
        • Angrist J.D.
        • Pischke J.-S.
        Mostly Harmless Econometrics: An Empiricist's Companion.
        Princeton University Press, Princeton2009

      Linked Article

      • The Impact of Marijuana Use on Glucose, Insulin, and Insulin Resistance among US Adults
        The American Journal of MedicineVol. 126Issue 7
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          There are limited data regarding the relationship between cannabinoids and metabolic processes. 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. To date, no study has investigated the relationship between marijuana use and fasting insulin, glucose, and insulin resistance.
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