Is marijuana use associated with lower inflammation? Results from waves III and IV of the national longitudinal study of adolescent to adult health.

Background: Some research suggests that marijuana use facilitates an anti-inflammatory response, yet the relationship between marijuana use and inflammation, as measured by C-reactive protein (CRP), remains poorly understood. The present study examined the association between recency of marijuana use and serum C-reactive protein levels in a nationally representative sample of adults.

Methods: Data from Waves III and IV (N = 13,166) of the National Longitudinal Study of Adolescent to Adult Health was utilized. Past 30 day marijuana use was assessed in Waves III and IV, and past year marijuana use was also assessed at Wave IV. CRP was dichotomized with a cutpoint of 3 mg/L. Logistic regression analyses examined the association between marijuana use and CRP levels at Wave IV.

Results: Past 30 day marijuana use was reported by 23.5% and 17.7% of participants at Wave III and Wave IV respectively, and 23.6% of participants reported past year marijuana use during Wave IV. Marijuana use was associated with lower CRP levels in bivariate analyses. However, these associations attenuated after adjusting for sociodemographic and health-related covariates.

Conclusions: Though marijuana and lower CRP levels were initially associated, the effect of marijuana use on CRP was later explained by gender, BMI, and anti-inflammatory medication use. This suggests that marijuana use does not confer an anti-inflammatory effect and recency of use is not relevant. Given expanding marijuana use legislation and discourse surrounding the consequences of marijuana for health, continued research is needed to elucidate the effect of marijuana on inflammation and subsequent risk of chronic disease.