A chemical in the brain and body that helps control mood, sleep, appetite, and other functions. It is often linked to feelings of well-being and happiness.
From 'sero-' based on 'serum' (the clear part of blood) + 'tonin' from 'tonic', because it was first found in blood serum that affected blood vessel tone. It was named in the mid-20th century as scientists studied neurotransmitters.
Serotonin isn’t just a 'happiness chemical'—it also affects digestion, blood flow, and more, so mood is only part of its job description. Many antidepressants work by changing how long serotonin hangs around between brain cells, tweaking the brain’s internal conversation.
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