However, the significant association between CSF MCP-1 and ALS was lost for the ES generated by mean concentration, s.d. and sample size group (12 studies, Hedges' g = 0.459, 95% CI = −0.011 to 0.93, P = 0.056), and the heterogeneity increased approximately 10% (Q = 48.921, d.f. = 11, I2 = 77.515, P < 0.001). Here, CCL2 is linked to amyotrophic lateral sclerosis.