system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What causes people to sleep walk?

This morning I woke up to a kitchen full of snack wrappers and sugar all over my counters; but neither my bf or me remembers getting up and snacking in the middle of the night (or why the sugar was out and everywhere). So either one of us sleep walked or someone broke in last night and helped themselves to some snacks. Either way, it’s made me wonder- what causes people to sleep walk?
gpt
You don’t dream right away during a sleep cycle.  Right before your dreaming period begins, your body releases chemicals that have a paralyzing effect.  So when you dream, your body doesn’t really move much, just your eyes (REM stands for rapid eye movement).  For a typical person, dreaming ends before the paralyzing effect wears off.

In a sleep walker, the dreaming period outlasts the paralyzing effect.  This is usually caused by high serotonin levels (the natural version of melatonin).  Most people’s serotonin levels decrease as they approach puberty which is why most sleepwalkers are children.  High stress can trigger your body to produce more serotonin because your body thinks you need more deep, restful sleep.