Serotonergic Effects on Interoception
Interoception is the signalling, perception, and interpretation of internal physiological states. Much of the psychopharmacology of interoception is still undiscovered. However, psychiatric disorders associated with changes of interoception, including depressive, anxiety, and eating disorders are often treated with selective serotonin reuptake inhibitors (SSRIs). The causal effect of acute changes of serotonin transmission on interoceptive cognition was tested by a within-participant, crossover, placebo-controlled study. Forty-seven healthy human volunteers (31 female, 16 male) were tested both on and off a 20mg oral dose of the commonly prescribed SSRI citalopram. For each randomly ordered session, participants made judgments on the synchrony of their heartbeat to auditory tones and expressed confidence in each of these judgments. Citalopram enhanced insight into the likelihood that ones interoceptive judgment had been correct, driven primarily by enhanced confidence for correct responses. This effect was independent of measured cardiac and subjective effects of the drug. This novel result is evidence that acute serotonin changes can alter metacognitive insight into the reliability of inferences based on interoceptive information, which is a foundation for considering effects of serotonin on cognition and emotion in terms of effective top-down regulation of interoceptive influence on mental states.