In this regard, it is interesting to note that although we did not observe an acute increase in plasma IL-4 post-WBH when compared to sham, exploratory linear mixed modeling indicated that, on a within-subjects basis, IL-4 immediately post-treatment was one of several cytokines associated with reduced HDRS depression scores across the 6-week follow-up period (F(1,97.9) = 5.61, p = 0.020). This evidence concerns the gene IL4 and major depressive disorder.