Sleep is supposed to be simple, right? You close your eyes, drift off, and wake up ready to face another day. But a new study published in PLOS Biology suggests that what happens between those two points says far more about your brain and body than you might think. Researchers at Concordia University identified five distinct “sleep profiles,” each tied to a specific mix of mental health, cognitive ability, and behavior.

They analyzed data from 770 healthy young adults as part of the Human Connectome Project, which combines MRI brain imaging with self-reported health and lifestyle information. The research points to sleep habits as biological signals, impacting everything from mood to focus and even aggression.

1. The Restless Mind

This group had the hardest time falling asleep and the l

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