HTR1A and myalgic encephalomeyelitis/chronic fatigue syndrome: Many signs, symptoms and anomalies of ME/CFS have been linked to 5HT (and downstream mediators), but studies involving SSRIs require cautious interpretation as these drugs initially increase extracellular 5HT, before activating the 5HT1A autoreceptors to decrease 5HT and induce effect (Andrews et al., 2015).