To the Editor: In their Research Letter, Dr Pacifici and colleagues1 found that long-term users of cannabis had lower natural killer cell counts, lymphocyte proliferation, and levels of interleukin 2 (IL-2), as well as increased levels of IL-10 and transforming growth factor-β-1. The authors concluded that this pattern of results may reflect immunosuppressive properties of cannabis.
These results are the opposite of those we recently reported in a randomized, double-blind, placebo-controlled study among patients with multiple sclerosis.2 - 3 We found that plant-derived cannabinoids promoted proinflammatory cytokine production (tumor necrosis factor and IL-12p40), with no change in lymphocyte proliferation, leukocyte subsets (CD4, CD8, CD14, CD15, CD16, CD19, CD45RA, CD45RO, and CD56), or other cytokines (IL-10 and IL-12p70).
We suspect that these divergent results reflect differences in the design of our study vs that of Pacifici et al. First, because their study was cross-sectional, their results may have reflected other confounding variables. Second, Pacifici et al obtained only a single blood sample from each patient. Other longitudinal studies, however, have found that circulating immune parameters fluctuate significantly over time.4 Finally, the study design of Pacifici et al was retrospective, in which dosing, timing, and constituents of the cannabis products were poorly defined. By contrast, a prospective study design can both include detailed inclusion criteria and carefully control the use of cannabis.
Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature
Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternal
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