ME/CFS patients have several unique traits compared to depression and fibromyalgia, including decreased serotonin (5-hydroxytryptamine, 5-HT) levels due to upregulation of the 5-HT transporter in astrocytes, which are reported to be related to autoimmune activity via an immune-inflammatory pathway [4]. Here, SLC6A4 is linked to myalgic encephalomeyelitis/chronic fatigue syndrome.