HTR5A and myalgic encephalomeyelitis/chronic fatigue syndrome: ME/CFS develops more in conditions of adversity (Heim et al., 2006; Nater et al., 2011), and patients show evidence of overactive limbic circuits (Nakatomi et al., 2014), elevated brain 5HT (Bakheit et al., 1992; Dinan et al., 1997; Sharpe et al., 1997), 5HT1A desensitization throughout the limbic system (Cleare et al., 2005), and numerous symptoms indicative of an inability to control the many functions modulated by 5HT (e.g., fatigue, proprioception, dyspnea, sensory sensitivity, dysautonomia, hypothyroidism, glucose control, immune function).