Serotonin is often referred to as the body’s “feel-good” neurotransmitter because of its powerful role in regulating mood, appetite, and emotional well-being. While serotonin is indirectly related to sleep — in fact, it's a precursor to melatonin — it is not the primary hormone responsible for regulating the sleep-wake cycle. The brain uses serotonin to help produce melatonin, but serotonin’s main functions lie in mood stabilization, anxiety regulation, and digestive function. While low serotonin levels can contribute to depression or sleep disturbances, they don’t directly initiate or manage the body's internal clock. Many antidepressants work by increasing serotonin levels, which can indirectly improve sleep, but this doesn’t make serotonin the main sleep hormone. That title goes to melatonin, which is triggered by darkness and actively guides your body toward sleep. Serotonin sets the stage, but melatonin cues the curtain to fall.