has primary input serotonin(1+) catabolic process phenol-containing compound catabolic process serotonin metabolic process serotonin catabolic process GO:0042429 Reactome:R-HSA-380612 serotonin breakdown serotonin catabolism serotonin degradation The chemical reactions and pathways resulting in the breakdown of serotonin (5-hydroxytryptamine), a monoamine neurotransmitter occurring in the peripheral and central nervous systems, also having hormonal properties. indole-containing compound catabolic process primary amino compound catabolic process