TNF-α levels were significantly increased in both mania (SMD 1.74, 95% CI 0.88 to 2.59, P < 0.0001, I2 = 93%, k = 7, n = 515) and bipolar depression (SMD 2.09, 95% CI 0.82 to 3.36, P < 0.001, I2 = 94%, k = 6, n = 334) but not significantly different in euthymia (SMD 0.33, 95% CI −0.13 to 0.79, P = 0.16, I2 = 82%, k = 8, n =  522) (Fig. 3(a)). The gene discussed is TNF; the disease is bipolar disorder.