Serotonergic Effects on Interoception

Interoception is the signaling, perception, and interpretation of internal physiological states. A causal link between serotonin and interoception was tested by a within-participant, crossover, placebo-controlled study. Forty-seven healthy human volunteers were tested on and off a 20mg oral dose of the selective serotonin reuptake inhibitor (SSRI) citalopram. For each randomly ordered session, participants made a series of judgements about the synchrony of their heartbeat to auditory tones and expressed confidence in each judgement. Citalopram enhanced insight into the likelihood that a correct interoceptive judgement occurred, driven primarily by increased confidence in correct judgements. This effect was independent of measured physiological and subjective effects of the drug and greater than a null effect on insight into exclusively exteroceptive performance on a visual task. This finding provides a foundation for considering effects of serotonin on cognition, emotion, and behaviour in terms of higher order processing of interoceptive events.