Fig. 2From: Cytokines in primary headache disorders: a systematic review and meta-analysisForest plots of IL-6, TNF-α, and IL-8 levels in migraine compared to healthy controls. Abbreviations: IL, interleukin; IV, inverse variance; I2, measure of heterogeneity; SD, standard deviation; TNF-α, tumour necrosis factor alphaBack to article page