Nicotine delays sleep onset by 10–30 minutes and reduces total sleep time, with evening use having the strongest effect REM sleep is suppressed by 15–30% in nicotine users, affecting dreaming, memory consolidation, and emotional regulation Evening vapers have 2–3x higher insomnia risk compared to non-users or morning-only vapers Sleep gets worse before it gets better after quitting — 1–3 weeks of withdrawal insomnia, then gradual improvement over 3–6 months Nicotine-free vapes have minimal sleep