New CED – Sleep and Drugs Practice Test

Sleep onset latency is the time it takes to fall asleep after lights out—the moment you first enter sleep, usually the first epoch of Stage N1 non-REM sleep. This measures sleep initiation, not how long the night lasts or when REM sleep begins. So if lights go off at 10:00 and you reach the first sleep stage at 10:15, the SOL is 15 minutes.