TNF and major depressive disorder: Participants with low levels of TNF-α were at reduced risk of MDD compared to participants with no TNF-α [those with a TNF-α of 1- <50 pg/ml titres had an aOR = 0.35(95% CI,0.10–1.16)], but as the level of TNF-α increased, the risk of MDD increased, and in particular participants with high levels of TNF-α (of 500 or above) were at a significantly increased risk of MDD [e.g. those with a TNF-α of 500- < 1000 pg/ml titres had an aOR = 3.98 (95% CI,1.29–12.33)] compared to participants with no TNF-α.