CRHR2 and myalgic encephalomeyelitis/chronic fatigue syndrome: This work hypothesizes that ME/CFS is caused by CRFR2 upregulation in the raphé nuclei and limbic system, observed in vivo (Waselus et al., 2009; Lebow et al., 2012; Wood et al., 2013), with symptoms explained by the known effects of CRFR2 activation on this subset of 5HT neurons (Waselus et al., 2005; Kirby et al., 2008; Lukkes et al., 2008).